15 course immunology كورس المناعة

3,765 views
3,605 views

Published on

Dr.Ehab

Published in: Education

15 course immunology كورس المناعة

  1. 1. *- Immune respons : its characterized by the produuction of proteins ( Igs) and specificially reactive lymphocytes (T-cells ) when an animal encounters a foreign macromolecules or cells. The inducing substances are called antigens i.e. antibody generators or immunogens.*- Immunogenicity : it the inherent ability of the immunogen (complete antigen ) to induce a specific immune response and to react with the products of this response (i.e. antibodies or the immune reactive lymphocytes) .*- Antigenicity : It is the ability of the foreign substance to react with the products of that response .Therefore, Antigens are the ligands that react with the products of an immune responseAlso, the immunogenicity & antigenicity are two interchangeable terms which will beused during discussion of the immune reponse during the period of this course.In addition, HAPTEN HAS AN ANTIGENICITY but HAPTEN PLUSPROTIEN CARRIER IS IMMUNOGEN
  2. 2. Overview of the Immune System Immune System Adaptive Innate (Specific) (Nonspecific) o line of defense 2 1o line of defense Protects/re-exposureCellular Components Humoral Components Cellular Components Humoral Components Interactions between the two systems
  3. 3. Comparison of Innate and Adaptive Immunity Innate Immunity Adaptive Immunity* No time lag * A lag period* Not antigen specific * Antigen specific* No memory developed Memory developed
  4. 4. Functions of the Immune System (Self/Non-self Discrimination)• To protect from pathogens • Intracellular (e.g. viruses and some bacteria and parasites) • Extracellular (e.g. most bacteria, fungi and parasites)• To eliminate modified or altered self
  5. 5. Infection and Immunity Balance infection immunity Bolus of infection x virulenceDisease = immunity
  6. 6. Effects of the Immune System• Beneficial: • Protection from Invaders • Elimination of Altered Self• Detrimental: • Discomfort and collateral damage (inflammation) • Damage to self (hypersensitivity or autoimmunity)
  7. 7. Innate (Nonspecific) Immunity
  8. 8. Innate Host Defenses Against Infection• Anatomical barriers – Mechanical factors – Chemical factors – Biological factors• Humoral components – Complement – Coagulation system – Cytokines• Cellular components – Neutrophils – Monocytes and macrophages – NK cells – Eosinophils
  9. 9. Anatomical Barriers - Mechanical FactorsSystem or Organ Cell type MechanismSkin Squamous epithelium Physical barrier DesquamationMucous Membranes Non-ciliated epithelium Peristalsis (e.g. GI tract) Ciliated epithelium (e.g. Mucociliary elevator respiratory tract) Epithelium (e.g. Flushing action of nasopharynx) tears, saliva, mucus, urine
  10. 10. Anatomical Barriers - Chemical FactorsSystem or Organ Component MechanismSkin Sweat Anti-microbial fatty acidsMucous Membranes HCl (parietal cells) Low pH Tears and saliva Lysozymes and Phospholipase A Defensins (respiratory & GI Antimicrobial tract) Sufactants (lung) Opsonin
  11. 11. Anatomical Barriers - Biological Factors System or Organ Component MechanismSkin and mucous Normal flora ☻Antimicrobial substancesmembranes ☻Competition for nutrients and colonization
  12. 12. Natural immune response (i-Humoral Components) Component MechanismComplement ☻- Lysis of bacteria and some viruses ☻- Opsonin ☻- Increase in vascular permeability ☻- Recruitment and activation of phagocytic cells ☻- With the help of antibodies, they can destroy the pathogensCoagulation ☻- Increase vascular permeabilitysystem ☻- Recruitment of phagocytic cells ☻- Β-lysine from platelets (a cationic detergent)Lactoferrin and ☻- Compete with bacteria for iron, therefore,transferrin cause bacterial death.Lysozymes ☻- Breaks down bacterial cell walls causing their lysis.Cytokines (Interleukins ☻- They had various immunological effects, Interferons)
  13. 13. Interferons (IFNs ) They are natural proteins produced by the cells of the immune system of mostvertebrates in response to challenges by foreign agents such as viruses, bacteria,parasites and tumor cells. Interferons belong to the largeclass of glycoproteins known as cytokines.;The discovery of interferonWhile aiming to develop an improved vaccine for smallpox, two Japanese virologists,working at the then Institute for Infection Disease at the University of Tokyo, noticed thatrabbit-skin or testis previously inoculated with UV-inactivated virus exhibited inhibitedviral growth inhibitory factor, and began to characterise it by fractionation of the UV-.irradiated viral homogenates using an ultracentrifuge:Functions of inteferons.Interferons in general have several effects in commonThey are antiviral and possess antioncogenic properties ►Macrophage and natural killer lymphocyte activation, and enhancement of major ►histocompatibility complex glycoprotein classes I and II, and thus presentation of.foreign (microbial) peptides to T cellsIn a majority of cases, the production of interferons is induced in response to ►microbes such as viruses and bacteria and their products (viral glycoproteins, viralRNA, bacterial endotoxin, bacterial flagella, CpG DNA), as well as mitogens and, tumor12interleukin- ,2interleukin ,1other cytokines, for example interleukinnecrosis factor and colony-stimulating factor, that are synthesised in the response.to the appearance of various antigens in the body
  14. 14. Their metabolism and excretion take place mainly in the liver and kidneys. They rarelypass the placenta and the blood-brain barrierType I interferonsIFN-α and IFN-β are secreted by many cell types including lymphocytes )NK cells, B-cells and T-cells), macrophages, fibroblasts, endothelial cells, osteoblasts and others.They stimulate both macrophages and NK cells to elicit and anti-viral response, andare also active against tumors. IFN-ω is released by leukocytes at the site of viral.infection or tumorsType II interferonsIFN-γ is involved in the regulation of the immune and inflammatory responses; inhumans, there is only one type of interferon-gamma. It is produced in activated T-cellsand natural killer cells. IFN-γ has some anti-viral and anti-tumor effects, but these are.generally weak1 However, this cytokine potentiates the effects of the type I IFNs. IFN-γ released by Thcells recruits leukocytes to a site of infection, resulting in increased inflammation. Italso stimulates macrophages to kill bacteria that have been engulfed. IFN-γ releasedcells is also important in regulating the1 by Thresponse. As IFN-γ is vitally implicated in the regulation of immune response, its 2 Thproduction can lead to autoimmune disorders
  15. 15. Autoimmune diseasesi-What are autoimmune diseases?Our bodies have an immune system that protects us from disease and infection. But ifyou have an autoimmune disease, your immune system attacks itself by mistake, andyou can get sick. Autoimmune diseases can affect connective tissue in your body (thetissue which binds together body tissues and organs). Autoimmune disease can affectmany parts of your body, like your nerves, muscles, endocrine system (system thatdirects your body’s hormones and other chemicals), and digestive system. Autoimmunity is the failure of an organism to recognize its own constituentparts (down to the sub-molecular levels) as "self", which results in an immuneresponse against its own cells and tissues. Any disease that results from such anaberrant immune response is termed an autoimmune disease. Autoimmune diseases,therefore are a large group of diseases characterized by abnormal functioning of theimmune system that causes your immune system to produce antibodies against yourown tissues - the prominent examples being Crohns disease, Diabetes Type 1,Coeliac disease, Systemic Lupus Erythematosus (SLE), Sjögrens syndrome andRheumatoid arthritis (RA). Prognosis of Autoimmune diseasesAlthough autoimmune diseases are chronic, the course they take is unpredictable.A doctor cannot foresee what will happen to the patient based on how the diseasestarts. Patients should be monitored closely by their doctors so environmental factors
  16. 16. or triggers that may worsen the disease can be discussed and avoided and new medicaltherapy can be started as soon as possible. Frequent visits to a doctor are important inorder for the physician to manage complex treatment regimens and watch for medicationside effects.Who is at risk for getting autoimmune diseases?Most autoimmune diseases occur in women, and most often during their childbearing years.Some of these diseases also affect African American, American Indian, and Latina women morethan white women. These diseases tend to run in families, so your genes, along with the wayyour immune system responds to certain triggers or things in the environment, affect yourchances of getting one of these diseases. If you think you may have an autoimmune disease,ask your family members if they have had symptoms like yours. The good news is that if youhave an autoimmune disease, there ARE things you can do to feel better!What are the most common symptoms of autoimmune diseases?There are more than 80 types of autoimmune diseases. Learning the symptoms of some of themore common autoimmune diseases can help you recognize the signs if you get one. But someautoimmune diseases share similar symptoms. This makes it hard for doctors to find out if youreally have one of these diseases, and which one it might be. This can make your trip to doctorslong and stressful. The most common symptoms of the autoimmune diseases includetiredness, depression , sensitivity to cold, weight gain, muscle weakness and cramps, dry hairtough skin, constipation and sometimes there are no symptoms
  17. 17. Natural immune response ii-Cellular ComponentsCell FunctionsNeutrophils ☻-Phagocytosis and intracellular killing ☻- Inflammation and tissue damageMacrophages ☻- Phagocytosis and intracellular killing ☻- Extracellular killing of infected or altered self targets ☻- Tissue repair ☻- Antigen presentation for specific immune responseNK and LAK cells ☻- Killing of virus-infected cells and altered self targetsEosinophils ☻- Killing of certain parasites
  18. 18. Phagocytosis andIntracellular Killing
  19. 19. Phagocyte Response to Infection • The Signals –N-formyl methionine-containing peptides –Clotting system peptides –Complement products –Cytokines released by tissue macrophages • Phagocyte response –Vascular adherence –Diapedesis –Chemotaxis –Activation –Phagocytosis and killing
  20. 20. Phagocytosis Steps of Phagocytosis •Attachment •Pseudopod extension •Phagosome formation •Granule fusion •Phagolysosome formation
  21. 21. Initiation of Phagocytosis Attachment via Receptors: IgG FcR Complement R ScavengerR Toll-like R
  22. 22. Phagocytes - Neutrophils (PNMs) ☻- Characteristic nucleus and cytoplasm ☻- specific granules ☻- CD 66 membrane marker
  23. 23. Phagocytes - Macrophages • Characteristic nucleus • Lysosomes • CD14 membrane marker
  24. 24. Natural Killer (NK) cells  Also known as large granular lymphocytes (LGL)  Kill virus-infected or malignant cells  Identified by the presence of CD56 & CD16 and absence of CD3  Activated by IL2 and IFN-γ to become LAK cells
  25. 25. What are Natural Killer Cells?Natural killer (NK) cells are an important first line of defense against newly arising malignant cells andcells infected with viruses, bacteria, and protozoa. They form a distinct group of lymphocytes with noimmunological memory and are independent of the adaptive immune system. Natural killer cellsconstitute 5 to 16 percent of the total lymphocyte population. Their specific function is to kill infected andMost of us have enough natural killer cells (cell .).cancerous cells (AAA Reference Laboratories, Inccounts) in our body, however many of us dont have enough natural killer cells that are active. Theseinactive natural killer cells are present in great numbers in our blood, lymph nodes, organs, and tissue,but they are not killing foreign invaders such as infectious organisms and malignant cells that constantlyaffect all of us.What You Should Know about Natural Killer Cells Activity?It is known that:Almost all cancer patients have very low levels of natural killer cell activity: usually 0 to 20Many patients with chronic diseases including Fibromyalgia and Chronic Fatigue Syndrome have low levels inthe range of 10 to 30.A wide variety of Auto Immune Disorders including Rheumatoid Arthritis, Lupus, Multiple Sclerosis andothers have low levels in the 10 to 30 rangeMost patients with chronic and/or recurrent infections (such as Staph, Sinusitis, Bronchitis, Tonsillitis,Pneumonia, and ear infections, etc.) have low levels in the 10 to 50 rangeMany patients with symptomatic EBV, CMV, HPV and other chronic viral infections are in the 0-20 rangeIt is also known that, there is a direct age related decrease in natural killer cell activity from 20 to 80yearsof age which may partially explain why the risk of cancer increases with each decade of lifeLow natural killer cell activity is a significant independent risk factor for the future development of cancer,as well as other chronic diseases and illnesses. Also, low natural killer cell activity is a strong predictor of poor prognosis of survival for cancer patients.Therefore, the higher the natural killer cell activity in patients with cancer the better their prognosis is forsurvival
  26. 26. Non-specific Killer CellsNK and LAK cells They all kill foreignADCC (K) cell and altered selfActivated macrophages targetsEosinophils
  27. 27. Intracellular Killing Pathways a-Respiratory Bursta-1- Oxygen-Dependent Myeloperoxidase-Independent Reactions + G-6-P-dehydrogenaseGlucose +NADP Pentose-P + NADPH NADPH oxidase - NADPH + O2 NADP++ O2 Cytochrome b558 - Superoxide dismutase 2O2 + 2H+ H2O2 + 1O2 - - 2O2 + H2O2 OH* + OH + 1O2Toxic compounds are : Superoxide anion (O2 -), Hydrogen peroxide (H2O2), Singlet oxygen (1O2) and Hydroxyl radical (OH*)
  28. 28. Respiratory Burst (continued) a-2- Oxygen-Dependent Myeloperoxidase-Dependent Reactions - myeloperoxidase - H2O2 + Cl OCl + H2O - 1O - 2OCl + H2O 2 + Cl + H2OToxic compounds: Hypochlorous acid (OCl-), and Singlet oxygen (1O2)
  29. 29. Respiratory Burst (continued) Detoxification Reactions Superoxide dismutase -2O2 + 2H+ H2O2 + O2 Catalase 2 H2O2 H2O + O2
  30. 30. b-Oxygen-Independent Killing in the PhagolysosomeEffector Molecule Function Damage to microbialCationic proteins (cathepsin) membranes Hydrolyses mucopeptidesLysozyme in the cell wallLactoferrin Deprives pathogens of ironHydrolytic enzymes (proteases) Digests killed organisms
  31. 31. Summary of Intracellular Killing Pathways Intracellular Killing Oxygen Oxygen Dependent IndependentMyleoperoxidase Myleoperoxidase Dependent Independent
  32. 32. Nitric Oxide Dependent Killing TNF TNF Nitric Oxide Nitric Oxide
  33. 33. Lymphokine Activated Killer (LAK) cell kills kills transformed malignant and malignant cells cells
  34. 34. Regulation of NK Cell Function •MHC I •KIR •KAR •KAL •No Killing •Killing
  35. 35. Their metabolism and excretion take place mainly in the liver and kidneys. They rarelypass the placenta and the blood-brain barrierType I interferonsIFN-α and IFN-β are secreted by many cell types including lymphocytes )NK cells, B-cells and T-cells), macrophages, fibroblasts, endothelial cells, osteoblasts and others.They stimulate both macrophages and NK cells to elicit and anti-viral response, andare also active against tumors. IFN-ω is released by leukocytes at the site of viral.infection or tumorsType II interferonsIFN-γ is involved in the regulation of the immune and inflammatory responses; inhumans, there is only one type of interferon-gamma. It is produced in activated T-cellsand natural killer cells. IFN-γ has some anti-viral and anti-tumor effects, but these are.generally weak1 However, this cytokine potentiates the effects of the type I IFNs. IFN-γ released by Thcells recruits leukocytes to a site of infection, resulting in increased inflammation. Italso stimulates macrophages to kill bacteria that have been engulfed. IFN-γ releasedcells is also important in regulating the1 by Thresponse. As IFN-γ is vitally implicated in the regulation of immune response, its 2 Thproduction can lead to autoimmune disorders
  36. 36. Autoimmune diseasesAutoimmunity is the failure of an organism to recognize its own constituent parts(down to the sub-molecular levels) as "self", which results in an immune responseagainst its own cells and tissues. Any disease that results from such an aberrantimmune response is termed an autoimmune disease. Autoimmune diseases, thereforeare a large group of diseases characterized by abnormal functioning of the immunesystem that causes your immune system to produce antibodies against your owntissues - the prominent examples being Crohns disease, Diabetes Type 1, Coeliacdisease, Systemic Lupus Erythematosus (SLE), Sjögrens syndrome and Rheumatoidarthritis (RA). Prognosis of Autoimmune diseasesAlthough autoimmune diseases are chronic, the course they take is unpredictable. Adoctor cannot foresee what will happen to the patient based on how the diseasestarts. Patients should be monitored closely by their doctors so environmental factorsor triggers that may worsen the disease can be discussed and avoided and newmedical therapy can be started as soon as possible. Frequent visits to a doctor areimportant in order for the physician to manage complex treatment regimens andwatch for medication side effects.
  37. 37. What are autoimmune diseases?Our bodies have an immune system that protects us from disease and infection. But ifyou have an autoimmune disease, your immune system attacks itself by mistake, and youcan get sick. Autoimmune diseases can affect connective tissue in your body (the tissuewhich binds together body tissues and organs). Autoimmune disease can affect manyparts of your body, like your nerves, muscles, endocrine system (system that directs yourbody’s hormones and other chemicals), and digestive system.Who is at risk for getting autoimmune diseases?Most autoimmune diseases occur in women, and most often during their childbearingyears. Some of these diseases also affect African American, American Indian, and Latinawomen more than white women. These diseases tend to run in families, so your genes,along with the way your immune system responds to certain triggers or things in theenvironment, affect your chances of getting one of these diseases. If you think you mayhave an autoimmune disease, ask your family members if they have had symptoms likeyours. The good news is that if you have an autoimmune disease, there ARE things youcan do to feel better!What are the most common symptoms of autoimmune diseases?There are more than 80 types of autoimmune diseases. Learning the symptoms of someof the more common autoimmune diseases can help you recognize the signs if you getone. But some autoimmune diseases share similar symptoms. This makes it hard fordoctors to find out if you really have one of these diseases, and which one it might be.This can make your trip to doctors long and stressful. The most common commonsymptoms of the autoimmune diseases include tiredness depressionsensitivity to cold weight gain muscle weakness and cramps dry hair tough skinconstipation sometimes there are no symptoms
  38. 38. What are Natural Killer Cells?Natural killer (NK) cells are an important first line of defense against newly arising malignant cells andcells infected with viruses, bacteria, and protozoa. They form a distinct group of lymphocytes with noimmunological memory and are independent of the adaptive immune system. Natural killer cellsconstitute 5 to 16 percent of the total lymphocyte population. Their specific function is to kill infected andMost of us have enough natural killer cells (cell .).cancerous cells (AAA Reference Laboratories, Inccounts) in our body, however many of us dont have enough natural killer cells that are active. Theseinactive natural killer cells are present in great numbers in our blood, lymph nodes, organs, and tissue,but they are not killing foreign invaders such as infectious organisms and malignant cells that constantlyaffect all of us.What You Should Know about Natural Killer Cells Activity?It is known that:Almost all cancer patients have very low levels of natural killer cell activity: usually 0 to 20Many patients with chronic diseases including Fibromyalgia and Chronic Fatigue Syndrome have low levels inthe range of 10 to 30.A wide variety of Auto Immune Disorders including Rheumatoid Arthritis, Lupus, Multiple Sclerosis andothers have low levels in the 10 to 30 rangeMost patients with chronic and/or recurrent infections (such as Staph, Sinusitis, Bronchitis, Tonsillitis,Pneumonia, and ear infections, etc.) have low levels in the 10 to 50 rangeMany patients with symptomatic EBV, CMV, HPV and other chronic viral infections are in the 0-20 rangeIt is also known that, there is a direct age related decrease in natural killer cell activity from 20 to 80yearsof age which may partially explain why the risk of cancer increases with each decade of lifeLow natural killer cell activity is a significant independent risk factor for the future development of cancer,as well as other chronic diseases and illnesses. Also, low natural killer cell activity is a strong predictor of poor prognosis of survival for cancer patients.Therefore, the higher the natural killer cell activity in patients with cancer the better their prognosis is forsurvival
  39. 39. Complement: HistoryDiscovered in 1894 by BordetIt represents lytic activity of fresh serumIts lytic activity destroyed when heated at 56C for 30 min
  40. 40. Complement functions• Host benefits: – Opsonization to enhance phagocytosis – Phagocyte attraction and activation – Lysis of bacteria and infected cells – Regulation of antibody responses – Clearance of immune complexes – Clearance of apoptotic cells• Host detriments: – Inflammation, anaphylaxis
  41. 41. Proteins of the complement system (nomenclature)• C1(qrs), C2, C3, C4, C5, C6, C7, C8, C9• factors B, D, H and I, properdin (P)• mannose binding lectin (MBL), MBL associated serine proteases (MASP-1 MASP-2)• C1 inhibitor (C1-INH, serpin), C4-binding protein (C4-BP), decay accelerating factor (DAF), Complement receptor 1 (CR1), protein- S (vitronectin)
  42. 42. Definitions• C-activation: alteration of C proteins such that they interact with the next component• C-fixation: utilization of C by Ag-Ab complexes• Hemolytic units (CH50): dilution of serum which lyses 50% of a standardized suspension of Ab-coated r.b.c• C-inactivation: denaturation (usually by heat) of an early C-component resulting in loss of hemolytic activity• Convertase/esterase: altered C-protein which acts as a proteolytic enzyme for another C-component
  43. 43. Activation product of complement proteins (nomenclature)Activated component are usually over-lined: e.g.C1qrsWhen enzymatically cleaved, the larger moiety,binds to the activation complex or membraneand the smaller peptide is released in themicroenvironmentLetter “b” is usually added to the larger,membrane-binding, peptide and “a” to thesmaller peptide (e.g., C3b/C3a, C4b/C4a,C5b/C5a), EXCEPT C2 (the larger, membrane-binding moiety is C2a; the smaller one is C2b)
  44. 44. Pathways of complement activationCLASSICAL LECTIN ALTERNATIVE PATHWAY PATHWAY PATHWAY antibody antibodydependent independent Activation of C3 and generation of C5 convertase activation of C5 LYTIC ATTACK PATHWAY
  45. 45. Components of the Classical Pathway C3 C4C1 complex
  46. 46. Classical PathwayGeneration of C3-convertase
  47. 47. Classical PathwayGeneration of C3-convertase _____ C4b2a is C3 convertase C4b
  48. 48. Classical PathwayGeneration of C5-convertase ________ C4b2a3b is C5 convertase; it leads into the Membrane Attack Pathway C3b C4b
  49. 49. Biological Activities of Classical Pathway ComponentsComponent Biological ActivityC2b Prokinin; cleaved by plasmin to yield kinin, which results in edemaC3a Anaphylotoxin; can activate basophils and mast cells to degranulate resulting in increased vascular permeability and contraction of smooth muscle cells, which may lead to anaphylaxisC3b Opsonin Activation of phagocytic cellsC4a AnaphylaotoxinC4b Opsonin 54
  50. 50. C1-inhibitor deficiency:hereditary angioedema
  51. 51. Components of mannose-binding lectin pathway MBL MASP1
  52. 52. Mannose-binding lectin pathway _____ C4b2a is C3 convertase; it will lead to the generation of C5 convertase MASP1 MBL
  53. 53. Components of the alternative pathwayC3
  54. 54. Spontaneous C3 activationGeneration of C3 convertase C3 i b C3b C3iBb complex has a very short half life
  55. 55. C3-activation the amplification loopIf spontaneously-generated C3b is not degraded C3b b C3 b
  56. 56. C3-activationthe amplification loop C3 b b C3b C3b
  57. 57. General IntroductionThe immune system is a set of mechanisms that protect an organism from◙.infection by identifying and killing pathogensThis task is extremely difficult, since pathogens range from viruses to parasitic worms ◙. and these diverse threats must be detected with absolute specificity amongst normal cells and tissuesPathogens are also constantly evolving new ways to avoid detection by the immune ◙.system and successfully infect their hosts.To meet this challenge, multiple mechanisms have evolved to recognize and neutralize pathogens ◙These mechanisms include antimicrobial peptides called defensins, pattern ◙.recognition receptors, and the complement systemMore sophisticated mechanisms, however, developed relatively recently, with the ◙evolution of vertebrates. The immune systems of vertebrates such as humansconsist of many types of proteins, cells, organs, and tissues, which interact in an.elaborate and dynamic networkAs part of this more complex immune response, the vertebrate system adapts over ◙.time to recognize particular pathogens more efficientlyThe adaptation process creates immunological memories and allows even ◙more effective protection during future encounters with these pathogens.This.process of acquired immunity is the basis of vaccination
  58. 58. General Introduction (continued)◙Disorders in the immune system can cause diseases.◙Immunodeficiency diseases occur when the immune system is less active than normal, resulting in recurring and life-threatening infections.◙Immunodeficiency can either be the result of a genetic disease, such as severe combined immunodeficiency, or be produced by pharmaceuticals or an infection, such as the acquired immune deficiency syndrome (AIDS) that is caused by the retrovirus HIV .◙In contrast, autoimmune diseases result from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Common autoimmune diseases include rheumatoid arthritis, diabetes mellitus type 1 and lupuserythematosus.◙ Therefore, immunity or the resistance is the sum of all naturally occurring and acquired defense mechanisms that protect the organism from infectious diseases.and the study of this mechanisms that a host has evolved to get rid itself of pathogens and other foreign substances.◙The immune system so, has at least three major functional properties that distinguish it from all the bodys other defenses:
  59. 59. Immunity (resistance):It the sum of all naturally occurring defense mechanismsthat protect the organism (or host) from infectiousdiseases. In addition, it include the study of themechanisms that a host has evolved to get rid itself fromthe invading pathogens and other foreign substances.. immune system so, has at least three majorThefunctional properties that distinguish it from all the bodysother defenses:The first: Is its extreme specificity, the ability to recognize and distinguish among a large or vast number of different target molecules, and to respond (or not respond) to each of these individually
  60. 60. Second: The immune system discriminates between self (body ingredients ) and non self ( foreign bodies), so that it normally coexists peacefully with all of the immunerable proteins and other organic materials that make up the host but responds vigorously against foreign substances, including cells or tissues from other people .Third: The immune system has memory, that is, the ability to be molded by its experiences so that subsequent encounters with a particular foreign pathogen provoke more rapid and more vigorous responses than occurred at the initial encounter.
  61. 61. A- Non a specific or innate immune response:This consists of the pre-existing defenses of ananimal, such as barrier layers and secretions.It has the following properties: i- It does not exhibit high specificity. ii- It does not depend on a complete (specific) recognition of the antigen. iii- A single mechanism protect against many pathogen. B- Specific or adaptive immune response: This response involves the cells of the immune system and frequently leads to a stateof immune memory, and finally destroying theinvading organisms.
  62. 62. Comparison between the non-specific and the specific immunity Non-specific Immunity Specific Immunity Response is antigen- Response is antigen- independent (Not antigen- dependent (antigen-specific) specific)There is immediate maximal There is a lag time between response exposure and maximal responseExposure to the Pathogen did Exposure to the Pathogen not produce immunological produce immunological memory memory
  63. 63. 2- The Non-Specific (Innate Immune) Response1- First defense line: a-Anatomical barriers: - Skin which physically preventing the interaction between the host and the pathogen. - Intestinal movement and mucus coating their walls. - Oscillation of broncho-pulmonary cilia. b-secretory molecules: -These secretions include organic acids in skin secretions, thiocyanate in saliva, low molecular weight fatty acids, bile acids in lower gastric intestinal tract, transferring, lactoferrin, lyzozyme, interferons, fibronectin, complement, etc. in serum, interferons and tumor necrosis factor at the site of inflammation.
  64. 64. 2. Second defense line: They represent the Cellular components, and they include phagocytic cells either polynuclear phagocytes or mononuclear phagocytes and NK cells. Polynuclear phagocytes: Neutrophils (Polymorph nuclear cells PMNs) are the most important cellular components in bacterial destruction. They are relatively large and most abundant white blood cells (65% of leucocytes) with lobed nucleus and cytoplasmic granules (lysosomes All phagocytic cells have receptors for a variety of molecules. Most pertinent to non-specific immune response are receptors for IgG-Fc, complement, interferon, TNF and certain bacterial components. Receptor interactions with these ligands promote phagocytosis and activation for efficient killing of pathogens
  65. 65. The figure shows a Neutrophil in a blood film Example of Phagocytosis: A macrophage attacking E.coli
  66. 66. Chemotactic response to inflammatory stimulus And the steps of this type of response1- Adherence 2- Diapedesis 3- going to the inflammatory site 4- Re-activation of adherence via histamine and thrombin secretions.
  67. 67. Histopathology of bladder shows eggs ofSchistosoma haematobium surrounded by intenseinfiltrates of eosinophils
  68. 68. 3-Front defense line: The major physiologic roles of natural killer cell (NK cells) appear to be in the early host defense against microbial agents. Nk cells, therefore, help to protect against a range of infections before the T-cell and B-cell response have developed. NK cells may thus function as a bridge between the innate and the acquired immune systems, acting as a front line of defense , while producing cytokines to promote the development of a specific immune response.NK cells and their activation
  69. 69. 1- Derived from bone marrow.2- Lack most markers for T and B cells (no TCR or CD3).3- Don’t undergo thymic maturation.4- Express CD56, a specific NKs marker5- Express a low affinity receptor for Fc portion of IgG called FcR (CD16), also expressed on granulocytes and macrophages.6-Cytokines especially IL -2 promotes further differentiation in to lymphokine – activated killer cells (LAK).
  70. 70. Acute-phase ResponseMost soluble mediators of innate immune response arefound in relatively small amounts, with the exception of C3,in the serum under normal conditions.The concentrations of several of these proteins, however,can increase as much as 1000-fold during seriousinfections, as part of accordinated protective reaction calledthe hepatic acute-phase-response. In this response, theliver temporarily increases its synthesis of more thanadozen different serum proteins that participate in anti-microbial defense, including complement factors C3 and B,the mannose binding proteins, C-reactive protein, serumamyloid protein P, and others.The response occurs when hepatocytes are exposed tocertain cytokines
  71. 71. 3.1 Cells of the immune system
  72. 72. Immunity (resistance): It the sum of all naturally occurring defense mechanisms that protect human from infectious disease Non – specific Specific Naturally acquired ( Innate ) ( Acquired )- Mucous membranes- Phagocytic cells - Placental transfer of antibodies( Passive )- Enzymes in secretion - Recovery from disease ( Active )-Interferons ( α,β,γ) - - Administration of antitoxin ( Passive )- NKCs- - Vaccinations ( Active )-Skin-. Macrophages- Artificially acquired
  73. 73. Natural ( Innate ) Specific ( Adaptive )-Less specific . or- Skin & mucous membrane . (Acquired)-NK cells .- Complement cascade .- Phagocytosis .- C- reactive protein . Active Passive-Induced by contact with foreign antigens .- - Induced by antibody performed in -- Consist of clinical infection , immunization with live or - another host- killed infectious agents or their toxins . - - Ab injected in the incubation period -- Long term. - - Short term .
  74. 74. Naturally acquired Artificially acquiredactive passive active passiveFirst: Non – specific Immunity ( Innate):- This is a physiologic mechanism which is inherent or innate with the - following properties A single mechanisms Do not depends on specific Protect It does not exhibit specificity recognition of a foreign Against material many paths
  75. 75. Definition :- the body forms his OWN IMMUNITY when stimulated (sensitized ) by introduction of immunogenic agent. Natural InfectionTypes *living attenuated vaccine * killed vaccine . Artificial bacterial products *Endotoxins. * Exotoxins. Others .Characters :- * slowly developed . *longer duration(and leave a potential immunity , so there is A rapid response in the future to the Same antigen ) leads to ?? *-Homogenous antibodies *- Cellular defense mechanism play a role Mechanism of Acquired immunity :- Humeral Ab Cellular T_Cells
  76. 76. classification of acquired Immunity:-- passive Acquired Immunity :-Definition: acquired Immunity by given already form antibodies or antitoxic serum or gammaglobulins from normal or convalescent individuals or Trans placental or lactation . Trans placental . NaturalTypes Lactation (Colostrum). Antitoxin serum tetanus. (Anti_ cobra venom) Artificial Gamma globulins.- characters :- * -Rapidly developed . * -Short duration .[ Rapidly eliminated in 2-4 WKS due to the formation of anti – antibodies (a disadvantage )]. *-Heterogeneous antibodies . * -Cellular mechanism not stimulated . (No memory ).* - Side effects:- *- Hyper sensitivity reactions against the foreign serum *-Neurological affection in some cases ( Encephalitis ). *-Superadded in infections e.g. (AIDS & HEPAT) .
  77. 77. - Humoral immunity - Cellular immunity . Antibody mediated immunity. - Cell mediated immunity . ( B- lymphocyte) - (T- lymphocytes-Mediated) help help CD4 CD8 B- lymphocyte Helper T- LYMPH . Cytotoxic T-lymphocyte(Protection is mediated bythe produced antibodies) TH1 TH2
  78. 78. Haematopoietic stem cell Lymphoid stem cell Myeloerythroid progenitor NK cellB-lymphocyte T-lymphocyte monocyte neutrophil eosinophil macrophage basophile RBC platelets
  79. 79. * B- Lymphocytes This cell type consists ( 20 – 25%) of the total peripheral lymphocytes n mammals , they mature in bone marrow , then, migrate to secondary lymphoid organs ( e.g. spleen & Lymph nodes ) .* Upon exposure to antigen , B-Lymphocytes are stimulated to proliferate ,(large lymphocytes) differentiate and mature into LARGE PLASMA CELLS * The large mature B-Lymphocytes have short life span ( days to weeks ) . Secreted Immunoglobulins or Humoral antibodies L-CHAIN Antibody H-CHAIN
  80. 80. * Some large mature B-Lymphocytes (B- cells ) can be converted into small B- cells which have long life span This type of cells isSecondary involved in the Immune Memory cells And serve asResponseActivation & differentiation of B-Lymphocytes , in certain instances , needs a Helper T- Lymphocytes activity to enhance the above toprocesses in that B-Lymphocytes.
  81. 81. T-Lymphocytes :-*- THEY CONSTITUTE 65 -80 10 of total peripheral lymphocytes .*- They have long life span ( months to years ).*- They mature in thymus gland before migrating to lymphoid organs*- Upon exposure to antigen , T -cell proliferate . How ever , their specific effectors molecules are not secreted and remains firmly Attached to their cellular membranes Giving what is called cell-mediated immune response*- They are involved in a variety of cell-mediated immunological responses defense against malignant cells graft rejection hyper sensitivity reactions bacteria & protozoa Fungi viruses
  82. 82. T-CELLST-HELPER (TH) T-SUPRESSOR(TS) T-CYTOTOXIC (TCs) T-DELAYEDT- Helper :Their Surface Antigen : is T4 (CD4) . Helper- *They Promote Maturation Of Antigen . *Stimulated B and T cells. Sensitivity And Cells ( TdH) Enhance their responseT – suppressor cells: * Their Surface antigen is T8(CD8). and * they suppress the effect of T – helper cells . T-CELL MEDIATED i.e. *Suppress T &B – response . IMMUNITYT –cytotoxrc: * their Surface antigen T8(CD). (Tcmi ) * they specifically destroy target cells.virus infected cells unacceptable grafted cells tumor cellsT – delayed hypersensitivity & T cell mediated immunity.CD4 (T4) *they are responsible for delayed hypersensitivity reactions to different antigens , particularly those of intra cellular parasites & contact allergen .In general : * some of the stimulated T-cells release soluble substanceslymphokines that modulate the behavior of other cells.
  83. 83. *- most antigens which have a small number of epitopes and require carrier needT – cell cooperation with B- cells for antibodies production . * Deficiency of B – cells (andor) T-helper cellsleads to defective synthesis of antibodies.* its over activity lead to Autoimmune disorders the majority of B-lymphocytes express both surface IgM & IgD, very few expresssurface IgG & IgA or IgE in the circulation.*the majority of B-cells also carry class 2 major histocompatibility complex )class ПMHC) products which are functionally important in Regulation of immune response
  84. 84. 2- T cell ActivationWhen a T cell encounters an antigen presenting cell (APC), the specificity ofits TCR determines the outcome.Only if the TCR recognizes its particular antigen MHC combination doesactivation occur.The recognition of appropriately presented antigen activates T cells toproliferate, differentiate and perform their effector functions. Activation of helper T-cells leads to the production of lymphokines thatpromote cellular and humoral immune responses, whereas activation ofcytotoxic T cells results in killing of the antigen bearing cells.
  85. 85. Co -operation of innate & specific Immunity in Host defense against infection *Antibodies promote Phagocytosis or activate complement to kill microbes *T-lymphocytes enhance phogocytic and microbial functions of macrophages INNATE IMMUNITY SPECIFIC IMMUNITY complement In direct lyses by C. + +BACTERIA PHOGOCYTE PHOGOCYTE Opsonization B-Lymph INEFFECTIVE BACTERIA And Phagocytosis Direct lyses + SERM Bacterial lyses + COMPLEMENT BACTERIA B-Lymph a Ab b LYSISBACTERIA s Cell + MediatedBACTERIA PHOGOCYTE bacteria T-Lymph response
  86. 86. Embryo Liver stem cell In Bone marrow central or primary lymphoid organs (tissues)SecondaryLymphoidOrgansSpleen or +Bone marrow + A9 A9 T_Cells B_Cells Effector PLASMA Killer cells memory cells CELLS B T HUMORAL ANTIBODIES
  87. 87. Specific memory and self-limitation of Immune response Ag A Secondary anti A infection response Serum Primary Anti A AB RESPONSE weeks 12 weeks*- Antigen enhance THE production of specific Antibody A.*- the secondary response to Ag A is more rapid and larger then the primary response ( memory cells ) .*- Antibodies Titer decline ( with time ) after each immunization .
  88. 88. Specific immune response : It is developed as a result of exposure to a variety of agents capable of inducing an immune response ( i.e. immunogens ) vaccines microbes that colonize Macro molecules in the diet in the bodyA special case Antigen in the form of hapten Hapten is a micomolecule may be conjugate with a carrier protein in the blood to be immunogen (antigen) Specific immune response Humoral cellular B. Cells T-CELLS *- They are two interrelated & interdependent mechanisms .
  89. 89. Specific immune response can be further Classified according to its components intoprimary secondaryInitial exposure to a particular on farther orInfectious agent or immunogen repeated exposureInduction phase of lymphocytes to antigen ( same )proliferation T-CELLS B-CELLS PLASMA CELLS increased resistance develops Sensitized T-CELLS Antibodies Cellular Immune response humoral through Humoral Cellular response response
  90. 90. Acquired immune responseHas both good ( desirable ) andBad ( undesirable ) consequence undesirable DesirableProtection Allergies (hypersensitivity)From infectionsagents Autoimmune diseases Immune responseControl ofPre-cancerous Graft rejectiongrowths
  91. 91. Interactions & functions of the major components of the immune systemANTIBODY – MEDIATED CELL MEDIATED REPONSE IMMUNE RESPONSE Two major componentsMain defense against T-HLPER & MACROPHAGES Cytotoxic* exteracellular, encapsulatedpathogenic bacteria Intracellular bacteria T-CELLSe.g. streptococci & staphylococci * ( mycobacterium &tuberculosis) Viruses*Neutralizations of toxins e.g.( • * Fungi Acts bytetanus) Destroying* viruses ) Hepatitis C,A,B…….(• Virus- infected cells
  92. 92. T-CELLS B-CELLS LYMPHOKINES HELPER CYTOTOXIC IL-2,IL-4.IL-5 CD4 CD8PLASMA CELL IL_2 IL_2ANTIBODIES Neutralize ACTIVATED HELPER Activated Toxins + AND MACRO PHAGES Cytotoxic cells COMPLEMENT + INHIBIT Kill NEUTROPHILS INTRACELLULAR Virus – infected Bacteria cells KILLING OF & BACTERIA fungi
  93. 93. VIRUS infection cell MHC Class I T-Cell receptor virus MHC Killing Class II CD8 IgM CYTOTOXIC T-Cell RECEPTOR B-CELLS CD4 ( T_HELPER ) INTERLEUKIN-4 INTERLEUKIN-5VIRUS ANTIGEN Defense mechanism against viral infectionVIRUS
  94. 94. *- Recognition of phases :- antigen recognition ( binding of Ag to specificreceptor on mature lymphocyte ( exist prior to ag exposure )*- activation proliferation & differentiation of lymphocytes is the sequenceof events induced in lymphocytes as result of Ag recognition .*- Effectors phases elimination of antigen [ is the stage of the responseAt which the sensitized cells perform the function that (eliminate of Ag)Some antigen – stimulated lymphocytes die by process called programmed celldeath ( apaptosis ). Elimination OF AgT OR + AgB Phagocytosis NATIVE complement LYMPHOCYTES Recognition ACTIVATION Effector programmed cell phase phase PHASE Death
  95. 95. Immunogenicety ability to induce immune responseAntigenicity ability of the substance to react specifically withimmune system must be Antigenic Immunogenic are not necessary to beHappen is incomplete antigen ( di nitro phenol or penicillin)It cannot stimulate humoral or cellular reactions but can react with theseproducts specifically so it is Antigenic not immunogenicIf they reacted with larger carrier protein (e.g., albumin , globulin orsynthetic poly peptide ) . It will be ImmunogenicAnimals injected with this hapten – proteinComplex will make antibodies to this hapten ,Only if it is ( hapten ) covalently linked tothe carrier (chemically bonded)
  96. 96. CARRIER HAPTEN ANTIBODYPRTOCAL PROTEIN i NO YES NO II YES NO Anti carrier only III YES YES Anti carrier only ( not chemically linked) IV YES YES Anti carrier (CHEMICALLY LINKED ) & Anti hapten
  97. 97. Immune response :- its characterized by the production of proteins called immunoglobulins( Igs) and specificially reactive lymphocytes (T-cells ), which carry their own effector molecules on their surfaces, whenan animal encounters a foreign macromolecules or cells .The inducing substances are called antigens i.e ( antibody generators )or immunogens*- Immunogenicity & antigenicity : Interchangeable terms used during discussion of the immune reponse. *- Immunogenicity : it the inherent ability of asubstance ( Immunogen (complete antigen ) to induce a specific immune response and to react withthe product of this response .*- Antigenicity : the ability of the inducing substance (Antigen) to react with the products of the immune response (i.e. the antibodies and|or the effector molecules of the T-lymphocytes). .HAPTEN HAS AN ANTIGENIC Properties but the HAPTEN PLUSPROTIEN CARRIER IS IMMUNOGEN Antigens are the a ligands that react with the products of animmune response .
  98. 98. Hapten-carrier conjugates have nativeantigenic determinants of the carrier aswell as new determinants of the hapten
  99. 99. Epitope ( - antigenic determinants ) :- are the sites either (on or) within the antigen with which antibodies or T-cells receptor reactsparatope :- the sites on antibodies which react with the antigen .epitope size ( small ) conformational linear conformational site are on antigen surface or internal that expressed only when the antigen has been partially degraded in vivovalency of antigen :- e.g multivalent i.e the antigen molecule carry a number of different epitopes ( some times 2 or>)some of which specify antibody A others specify antibody B .valency = total no . of epitopes the antigen pocesses .
  100. 100. Antigenic determinants are usually limited to those portions of the antigenthat are accessible to antibodies shownin black for this iron-containing protein
  101. 101. EPITOPE (ANTIGENIC DETEREMNANT):- The portion of Ag that binds specifically withthe binding site of Ab (paratope) or a receptor(s) on T_lymphocyteSIZE CONFORMATIONAL STRUCTURE The size and the structure of epitope are complementary to that of paratope.i.e. they must have approximately the same dimensionsWITH RESPECT TO THEIR STRUCTURE ,A g MAY HAVE THE FOLLOWINGCHRACTES :- Ag may have only a single epitope of a given specificity on its surface which iscapable to bind with antibodies , such Ag is called UNIVALENT AND UNIDETRMINANT(one kind of specificity ) for example hapten Ag may have two or more epitopes (which determine the specificity ), the A g inthis case is called MULTIVALENT (which determine the number).If the epitopes are of the same type, the Ag is called also UNIDETERMINANT(UNIDETERMINANT MULTIVALENT and if they are of different types calledMULTIDETERMINANT (specificity, MULTIDETERMINANT- MULTIVALENT ). UNIVALENT MULTIVALENT MULTIVALENT UNIDETREMNANT UNIDETREMINANT MULTIDETRMENANT
  102. 102. In an antigen, the same antigenic determinant repeated many times
  103. 103. T-dependent antigens are characterized by a few copies of many different antigenic determinants
  104. 104. .factors Affecting ImmunogenicityForeigness chemical complexity molecular sizeA – foreigness :-the immunogenic substance must be forign to prduce immune response . The greater the foreignness, the more will be the reponse *- identical twins smaller or no response *- brothers with the higher immune response same tissues compatibility the same blood groups .etc ………….B.CHEMICAL COMPLEXITY :-*- MOST of organic molecules are immunogenic expert lipids*- proteins are the strongest immunogenic substance .*-Polysaccharides most of them are haptens but they become complete Ag incases of * peneumococcal polysaccharide . * Lip polysaccharides in cell membrane of gram (– ve ) bacteria.
  105. 105. *- Glycoproteins :-Are immunogenic ex blood group Ags ( A,B,AB,O,RH )*- POLYPEPTIDES & nucleic acids :-Are weak immunogens*- lipids :- are not antigenic or immunogenicC.molecular size :- usually the larger the molecule the stronger the Immunogenicety .M.Wt below 5000 DA ARE NOT IMMUNOGENICMACRO MOLECULES are the most potent immunogens .( e.g. albumin m.wt 40.000 DaGlobulin m.wt 160 kDaMacrocyanin m.wt 1000 kDa
  106. 106. The valence of A.g increases proportionally with molecular size .Macro molecules are easily to induce phagocytic ( as example ) and easier to be phagocytosed Quaternary structure are the most ImmunogenicThe more complexity , the more Immunogenicety
  107. 107. Superantigens activate a large fraction of T cells in contrast to conventional T- dependent antigens
  108. 108. MULTIVALENT since it has only one kind of determinant but many of such determinant on each molecule Ex. Many poly saccharides & homo polymer (e-g peptide chain of the some .A. Acids .)*- some antigens are multi determinant & valent such molecules have manyepitopes of different kinds (multi specificity ) but only one of each kind ( monovalent ) Ex. Most proteins .*- High M.WT , chemically complexed compounds or polymerized proteins(quaternary structure or heteropolymerized proteins are usually .*-Multi determinant Ag ( multi specific) , multivalent Ag (more than oneepitope of each kind) )What kind &How many of such kind )
  109. 109. Antibody binding site ( Paratope ). Binding of Ag & AbAffinity :- the strength of attraction and binding between an epitope( monovalent ) of an Ag and the antigen combining site of Ab molecule ( Paratope).Avidity :- The strength with which ( multivalcnt ) Ag bind to itsantibodies ( Abs). ( chemical complexity ) This depends on the affinities of the individual combining sites of the determinants on the antigen
  110. 110. ANTIBODIES and their STRUCTURESElectrophoretic separation of serum proteins
  111. 111. ANTIBODY STRUCTUR *Classes of antibodies . IgM , IgG , IgE , IgA & IgD . CH1A = COMPLEMENT BINDING SITE Constant A Constant A CH2 Heavy chainB = NEUTROPHILS & MACRO- PHAGE BINDING SITE Hinge bonds Constant B Constant BVARIBLE = ANTIGEN BINDING SITE . CH3
  112. 112. The basic structure of immunoglobulins
  113. 113. Rotating antibody
  114. 114. ANTI BODIESPOLYCLONAL ANTI BODIES MONOCLONAL ANTIBODIES- INDUCED AGAINST WHOLE ANTIGEN . INDUCED AGAINST ONE EPITOPE .- LESS SPECIFIC (I.E . SMALL PART OF ANTIGEN )- PRESENT IN SERUM - MORE SPECIFIC . - PRODUCCED BY HYBRIDOMA EPITOPE EPITOPE TECHNOLOGY . INFECTION POLYCLONAL Ab. MONOCLONAL Ab MAb MAb MAb
  115. 115. i-Immunization II_ FUSION antigen + MICE + MYELOMA CELLS B-CELLS fusion TUMOR MICE MICEAscetic fluid selection of Desired Clonesupernatant Tissue cultureFluid HYPRID CELLS HybrIdoma technique
  116. 116. Immunoglobulins "Humoral antibodies”They are formed of two identical units each of them is formed of :- A) heavy chain B) light chain C) hing regionA) Light chain 2( lambda) but never 1 and 1K K ( Kappa ) 2B) Heavy chains :* M-Wt 53.000 - 75.000 Da*- heavy chains are hold together with (disulphide bonds) .*- Fixed region contain 2k or 2  .*- The variable region contain a mixture of K,.*- both L& H chains contains the following region : Light chain contain variable (VL) and hyper variable (VH) regions Heavy chain contain variable and hyper variable regions.
  117. 117. * Amino terminal * carboxyl terminal* The amino acids differ * A. As are similar in different on  to another specificity. * it contain the effectors domain which is responsible for the* The VL & VH are adjacent to initiation of the processeach other forming paratope . by which the body gets-rid of Ag. .* They have sub-regions of the variable region (hypervariable) It is responsible for Designation of Ab class & its These regions have extreme - distribution. variability in their A .As sequence in different antibodies - and they are responsible for binding with Ag(s) -. - )hyper variable ( CDRs}{ comptementary detemining regions
  118. 118. C) Hinge region :- * CH 1, CH 2 , CH 3 : occupies ¾ that of Heavy chains the other ¼ is VH . * The Hinge region lies between CH 1 & CH 2 . * It is flexible & allows movement between the two antibody binding sites . * The hinge region is digested by protease (e.g. pa pain ) which splits it into :-( i ) antigen binding fragments (fab) = They are 2 identical fragments containing theantigen binding site .)ii ) crystallization fragment (FC ):-It contains the effectors (
  119. 119. Structures and function Of Specific Immunoglabulins*- Ig(s) are glycoproteins in the gamma globulin fraction of serum proteins (albumin ,fibrinogen , globulins ( ,  and  ) .*- they are produced by B- lymphocytes or plasma cells in response on immunogen (or Ag ). General Ig structure :-*- 4 poly peptide chains.*- they are linked covalently by disulphide bonds*- the 4 chains , monomeric Ig structure ,arecomposed of 2 identical heavy poly peptide chains (H) 2 identical light poly peptide chains (L)*- Heavy and light chains :*- H- chain :*- Have a M.wt of 50-75 KD (Twice that of L chain )*- H chains contain  400 A.As (Twice that of L chain )*-A. As differences in the .COOH terminal portion of the heavy chain (CH) identify 5 distinct H-chains isotypes .
  120. 120. * Each H chain has 4 or 5 domains :1 domain in the variable and 3 or 4 in the constant3 IgG (  ), IgA( )&IgD( ) Or 4 Igm ( )&IgE(  )Total = 1 Variable + 3 constant or = 4constant +1 Variable Notes (1) -Each L- chain has 2 domains 1 VL 1 CL (2)- Folding of the polypeptides chains brings the hyper variable regions of the VH and VL domains into close proximity . (3)- this folding creates a 3-dimensional structure that is complementary to the epitope (last figure ) The Hinge region*- It is the portion of the H-chain between CH 1& CH 2.*- there is no homology between it and the other H- chain domains, thus .itssequence is unique (sole) for each Ig type and subclass
  121. 121. IgM & IgE do not possess a hinge region but have one more CH domain.These structure explain why both IgM & IgE have 4 domains on the CH chains butnot like the other types (which have only 3 domains on CH)*-In this region (hinge), inter chain disulphide bonds forms between the arms of the Fab fragments preventing them from folding and therefore , rendering this portion of the molecule highly susceptible to fragmentation by enzymatic attach .* -The hinge region is highly flexible and allows for movement of the Fab arms in relation to each other .This motility explain why native antibody molecule do not activate complement , whereas those in an immune complex do .This is because , the native Ab is not in the appropriate configuration t1/2 or half life of( Abs) .*- These heavy chain isotypes form the basis of the 5 Class of Immunoglabulins molecule IgG () ,IgA ( ) ,IgM ( ),IgD ( )and IgE ( ).*- H chains Classes  and  are subdivided into subclasses of molecules  1 , 2 , 3 , and 4 And   1 and  2
  122. 122. The subdivision is based on the greater similarity of A.As sequence shown bysubclasses of the same classi.e. 1 , 2 , 3 etc,. Than is shown by different classes (i.e.  ,  , or )*- The heavy chain subclasses determine immunoglobulin subclassese.g. 1 = IgG1 2 = IgG2 , 3 = IgG3 etc,.*-L-chains :- * Are composed of  200 A. As . * They are of 2 types ( K= Kappa or  = lambda ) . { based on their structural (antigenic) differences } * All Igs classes have 2K or 2 chains but not k or  k . ex. * The proportion of K/ = 3/2 (human Ig) .- chain Isotypes :-*- There is no isotypic variations in K chains*- There are 4 distinct  chains 4 different isotypes .*- All the 4 subclasses are present in each of the Ig classes i.e. in IgM , IgE , IgD etc.*- Disulphide bonds Hold together the 4 polypeptide chains in Ig molecules . -*There are 2 types of disulphide bonds-:
  123. 123. 1- Inter- chain disulphide bonds : occur between L – L chains H – H chains H – L chain Single L-L bond only in Hinge But also in Ig A2M (1) region COOH-terminal such bond can of the H chain occurs in all Ig(s)except occur under path- Ig A2M (1) which ogenic conditions. Lacks an inter chain (e.g. Bence JonesThey can be 1:15 depending disulphide bond protein ) seen inOn the class & subclass types urine of some patients with multiple myeloma
  124. 124. INTRA CHAIN DISULPHIDE BONDS :*- occurs within an individual chain .*- they are stronger than inter chain bonds .*- they no. of intra-chain disulphide bonds varies depending only on the number ofdomains in the molecular .Light chain have 2 intra-chain bonds .*- human IgG, IgA, IgD heavy chains have 4 intra_chain bonds*- human IgM , IgE heavy chains have 5 intra-chain bonds .*- Each H& L-Chain has a variable (v) and constant (c) region*- V region lies in the – NH2 terminal portion of the molecule .*- The V region has a wide variation in it’s A.A composition .*- The C region lies in the - COOH terminal end of the molecule .*- The C region has a much more constant A.A Sequence except for minor inheritedchanges
  125. 125. *- The variable regions associate with appropiate constant regions .so that a variable H – Chain regions (VH) does not occur in an variable L – Chain(VL) and Vise versa .*- However , a particular VH chain sequence may occur in more than oneH – Chain class ( i.e IgG, IgM , IgD ,IgA and IgE ) .*- Thus during class switching in an immune response e.g when B – cells changetheir production from IgM to IgG heavy chainonly the constant regions of the H (CH) changes and the antibody specificityremains the same .HYPER variable regions*- they are particular areas within the variable regionsThat are highly variable in A. As sequence .*- THESE hyper variable regions often called complentary determining regions*- THESE regions occurs at simillar A.A positions in an relatively invariantmolecules .
  126. 126. CDRs :- they are short polypeptide segments lining near A. As positions 30,50 CDR1 CDR2 CDR3 AND 90 in the variable regions of both L and H chains . FR1 FR2 FR3 FR4 variabilityFRs CDRS 89-97variable region 24-34 50-56 NO OF AgS Note :- the variability range ( index ) used is an arbitrary scales of the no. of different A.AS found in each position if 100 different Light chain were analyzed . *- the hyper variable regions are important in the structure of the Ag binding site ( paratope ) . *- L – chain have 3 hyper variable regions ( the last figure ) *- H – chain have 4 hyper variable regions although, ONLY 3 OF THE 4 have been associated with epitope recognition *- each Ig chain consists of a series of globular regions or domains enclosed by disulphide bonds ( intra or inter ) ?? Chain disulphide bond . *- The A.AS sequence of the domains show a high degree of homology ( i.e the sequences are very similar ) .
  127. 127. Structure of the variable region framework regions
  128. 128. Properties of Ig :- IgG IgA IgM IgD IgEH – CHAIN     H – CHAIN SUBCLASS 1, 2 1 2 - - -M.Wt 150 160-400 900 180 190Carbohydrate (%) 3 7 12 13 11Serum conc(mg %) 1200 200 120 3 0.05Seru t ½ ) days( 21 6 10 3 2Functions :-Complement activation ++ - ++++ - -Opsonization ++++ + - - -Antiviral activation ++ +++ + - ?Mast cell sensitization - - - - +
  129. 129. Immunoglobulin are glycoproteins :- (3-13 % of their M.WT ) OLIGOSACCHARIGES + PROTEIN*- THESE oligosaccharides are present in CH2 or CH3 .*- N -glycosidic bonds usually link N- acetylglucosamine in the carbohydrate moietyto asparagine residue in the peptide c-chain of Ab[ linkage with the enzyme N -acetylglucosamine .- Asparagine transglycosylase ] transferase*- t ½ of Abs in the circulation depends on the status of oligosaccharide side chain*- the oligosaccharide side chain of Ab terminate with galactose to which sialic acidis bind .*- when Abs have the sialic acid removed by the enzyme neuraminidase , theybecome susceptible to degradation in the liver .*- in this case the terminal galactase bind to a receptor on hepatocytes and theentire molecule is , then , interenalized to the cell for degradation viaProteolytic enzymes in lysosomes of the cells . Immunoglobulin fragments: Structure/function relationships
  130. 130. Digestion of Abs with Restriction enzymes (Immunoglobulin fragmentation) aswell as Structure/function relationships: S-S S-S F(ab)2 FC Ab
  131. 131. Restriction enzymes digestion of Abs :1) Papain : digest above hinge region so it leaves 2 Fab fragments each is monovalent S-SAnd crystalline fragment (FC) papain Fab FC Monovalent 2)Pepsin: digest away most of FCFragments below the Interchain disulphide bond(below the hinge region) it give one large fragmentsF(AB)2 which is consist of two Fabfragments joined by the disulphide bondThus , it is bivalent ,possessing the ability to bind and form agglutination S-S F(ab)2 FC Ab
  132. 132. Figure 4 Immunoglobulin fragments: Structure/function relationships
  133. 133. Classes of antibodiesThey are 5 isotypesThe class of Ab depends on the A.A: sequenceof the constant regions of the heavy chain . IgM*- Immunoglobulin M (IgM) :- * it is a pentamer ( 5 molecules ) . * they are linked together by disulphide bridges at the COOH terminal end of the heavy chains as well as an additional poly peptide chain ( joining chain) * this type of Ab account for 8-10% of the total PLASMA ANTIBODIES . * it is the most abundant Ab produced by the faetus . * it binds with viruses and bacteria*- Immunoglobulin g ( IgG ) :- * it is a monomer * it accounts of ~ 75 % of the total antibodies . * it is important for elicit ting the immune response to Ags * it is only antibody which pass through the placenta to protect the faetus.
  134. 134. *- immunoglobulin D ( IgD):- * It is a monomer ACCOUNTING FOR < 1% & TOTAL ANTIBODIS . * Its function is controversial .*- immunoglobulin E ( IgE):-* It is a monomer ( below 0.004 % & the total Abs)* It is present in spleen , tonsils , mucus membrane of lungs GI* On binding with ag it releases histamine from mast cells leading tohypersensitivity .* It provides immunity to intestinal parasites .*- immunoglobulin A ( IgA):-* MONOMER , DIMER or TRIMER( mostly dimer )* Like IgM the units are linked by disulphide and j chain * it is found in tears , saliva , intestinal treat secretions * it binds with Ag preventing them from tissue adherence , colonization ,andmaking them more phagocytosed .
  135. 135. Laboratory Methods SerologyIn vitro Ag & Ab reactions called serologyIt provide methods for i) Identification (Diagnosing) ( ii ) quantization of titre of Ab (and or) AgTitre : or the level of Ab (s) in the serum can be measured by using known AgThe titre may have diagnostic or prognosticEx. A rise in Ab titre between acute &convalescent serum can be used as adiagnostic tool for a specific diseaseThe titre is defined as the greatest dilution of serum (which contain the Ab underconsideration ) that reacts which the antigen ( i.e. gives +ve result ) .
  136. 136. - the forces involved in Ag-Ab reactions are greatly affected by various environmental factors :-*- The Ag- Ab complex is not bound firmly together .*_This complex may even dissociate spontaneously .* physiologic ph & salt concentration promote optimal union of them .*- the force of attraction tend to be weaker ina) very acidic .e.g. 0.01Mb) very alkaline medium i.e pH 4 and alkaline ( i.e. above pH 10 )- temperature :- it plays an important role : * the higher the temp ( up to 50 – 55 0 c ) , the more rapid is the rate of reaction between Ag & Ab . * the reason is the increase in kinetic motions of the reactants ( Ag & Ab )
  137. 137. various forces act to hold the Ag-Ab complex together :- * The maximum attractive forces stabilizing Ag-Ab complexesAre van der weal forces Ionic bonds 1- van der weal forces :- * occurs because of spatial fit ( the below fig ) * these forces of attraction hold Ag to Ab onlyWhen the two molecules have complementary shapes (a) puratope 2 puratope 2 Epitope 2 (a) (i) significant changes Epitope 2a In the shape of epitope 2 (b) Into 2a
  138. 138. these change precludes its ( 2a ) interactions with the matching binding site of theoriginal Ab .* When the molecules have less similar shapes ( b) , these forces are less effective(b)2-Ionic bonds :-* They are patterns of complementary electric charges on the molecule .* The electrostatic interactions tend to hold the molecules together . COO NH3 COO NH3+ COO +NH3Affinity :- the strength of attraction between a single epitope and its matchingparatope is the referred to as the affinity of the reaction between the two reactants . Ag-Ab complex of low affinity dissociate readilyAvidity :-* It is a related term to affinity* It refers to the strength of the interactions between multivalent antigens and thepopulation of Abs that they have included .
  139. 139. *- Avidity is influenced by the affinity of individual Abs for their (A) epitope (B) the valency of Ag and (C) the valency of Ab tertiary structure of protein : *- the ability of Ab to bind with Ag can be affected by altering the tertiary structure of any of themex. insulin which is composed of A&B chains Ab to either one of these chains can be produced by(a) splitting the chains(b) purifying tem(b) injecting ) .e.g. a pig)them into foreign host the pig will produces Ab to the particular chain that was injected *- if the host (pig) Abs are injected back into the animal species that supplied the original insulin (man) , the abs will not react with intact insulin molecules . *- This is because the tertiary structure of native insulin is such that the on the A & B chains are not accessible .. epitopes Now , it is generally accepted that in a given poly peptide the A .As that are spatially accessible because of Tertiary structure of this protein are only immune reactive
  140. 140. *- The physical state of the antigen is responsible for the identification of Ag –Abreactions and the naming of Abs .*- The same Ab molecule could , in fact , be described by each of the following terms :(1) Agglutinins are Abs that aggregate cellular Ags.(2) Lysins are abs that cause dissolution of cell membrane .(3) Precipitins are abs that form precipitate with soluble Ags .(4) Antitoxins are abs that neutralize toxins . procedures must be involving direct demonstration and observation of reaction .. The relative sensitivities of the tests for Ags and Abs are Presented in table 8.1 page 156 [ immunology , 3rd edn ].A- Agglutination Reactions :- a b Serve to detect and quantities Agglutinins and identify cellular Ags Bacterial cell white blood cells red blood cells .**-- when the cells intact with the appropriate Ab , they clump together and eventually Large enough to be visible form masses with naked eye
  141. 141. *- When Ab agglutinates bacteria in the body opsonization occur .*- Agglutination occurs because Abs and at least bivalent .*- Two sites on the Ab and multiple sites on the Ag Ag – Ab lattice formation that can build up into increasingly larges coupled lattice structure Example widal test :- (diagnostic test of typhoid )*-Ab of patient serum is measured by adding a constant mount Ag (e.g. salmonella typhi ) to serially diluted serum .*- After incubation , the test tubes are examined for visible agglutination .*- the last tube (i.e the highest dilation of serum ) showing agglutination is referred as the titre.
  142. 142. B- lyses Reactions :- In the presence of a complement an Ag – Ab reaction , on a cell membrane , may result in membrane damage that leads to cell lyses This phenomenon is important in the hosts defense against condition such as microbial infection or cancer ( graft cell , virus infected cells , etc…………….(*i)- Haemolysis :- In which the Hemoglobin is released from R.B.C, is a requisite phenomenon for the complement fixation test .*ii)-- bacteriolysis :- cells of gram (– ve) bacteria are undergoes immune lyses under certaincondition .*iii)-- cytolysis :- involves the destruction of other cells types (e.g. lymphocytes ). C- precipitation:- * occurs when the Ag is soluble instead of cellular *therefore a large number of molecules are required for lattice formation and alarge no .of lattice must be formed for an aggregate to be formed and visibly seen.
  143. 143. *when soluble Ag (s) come intact with specific Ab. They aggregate (i.e precipitate ) Three conditions are presentA- where the (Ag) is very low with excess Ab (zone of Ab excess ), Formation of complex occurs But Residual Ab remains in the supernatantB- As more Ag is added , large aggregate is formed In the (zone of equivalence) ,maximal Ag-Ab complex are formed and precipitatedC- Instead of reaching a plateau , this curve comes back down to zero with increasing the mount of Ag (zone of Ag excess ) * this is because the lattice size becomes too small to precipitate . * In extreme Ag excess . the complex will be trimmer i.e one Ab +2AgNote:- the soluble Immune complex are not processed efficiently by the reticuloendothelial system ,and ,this cause damage (how??)
  144. 144. Amount of precipitate Zone Of equivalence Effects of increasing amounts of Ag on the total immune precipitate obtained from a mixture of soluble Ag and its homologous AbINDIRECT HCG :Examples 1 :- determination( and or) detection of HCG by using indirect methods .(i) an Ag will be added ( HCG ) .(from the kit)(ii) Urine will be added ( excess Ag ) from a female may be pregnant .(iii) Ab to HCG will be added In case of positive In case of negative pregnancyA state of Ag excess a state of equivalence will be reachedTherefore, no precipitation therefore, precipitation occurDirect HCG assay :* (i) Ab to HCG will be added (from the kit)* (ii) Ag ( HCG of the test sample will be added) . If precipitation occur ( positive) if, no precipitation occur ( negative )
  145. 145. Hyaluronic acid (HA) assay using excessHA binding protein (HABP) :-* HABP will be added in excess ( known excess ) (ACT AS Ab)* Sample will be added ( containing HA) (ACT AS Ag)* [ A state of Ab excess no ppt ]* An radiolabelled HA will be added ( Ag )Thus, precipitation occur ( IF +ve sample) and immune complex will be separatedand quantities by radio- immune assay technique ,in case of no precipitation, thesample is negativeImmune diffusion* It used for quantization of Ag (s)* Thus, precipitate will also be demonstrated .* If an Ag – Ab reaction takes place in semisolid medium (e.g. agar ) , band ofprecipitate will be formed .* The reason of precipitation , is the diffusion of the components (Ag & Ab ) towardseach other .* A useful example is a double immune diffusion technique :-
  146. 146. Procedure :-* Ag& Ab preparations are placed in separate wells that are cut into a thin layer ofagar in a Petri dish .* The reactants diffuse towards each other through the agar until they meet anoptimal proportions [ zone of equivalence ] and forms ( ppt ) bands Solid Chevron Fig (a) Ag PPT Ag Zone of Ab equivalenceThe advantages of the procedure is that antigenic relationshipcan be detected by the precipitation pattern (s)
  147. 147. 3 basic patterns are given :(a)- in reaction of identity , the 2 Ags are similar , they will diffuse at the same rateand the two precipitations bonds merges into a solid chevron ( fig b) Aga Aga Fig b Ab2- in reactions of non-identity , the two Ags are completely different and the linesof the precipitate cross (fig c) Ayab Agac Aga Agb Fig c Aba Abb Aba Abb3- reaction of partial identity :-* It is indicated by spur formation indicating that one of theAg(s) is cross-reactive ( but not identical ) to the other one .* The spur occurs because one the Abs (b) does not react with the cross-reactingAg (Ag ac) but migrate past that Ag (Ag ac ) until it reaches an Ag (Ag ab ) that

×