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Immune system
- 2. Overview of the Immune System Immune System Innate (Nonspecific) 1o line of defense Adaptive (Specific) 2o line of defense Protects/re-exposure Cellular Components Humoral Components Cellular Components Humoral Components Interactions between the two systems
- 3. Innate Immunity Adaptive Immunity Comparison of Innate and Adaptive Immunity • No memory • No time lag • Not antigen specific • A lag period • Antigen specific • Development of memory
- 4. Cells of the Immune System Immune System Myeloid Cells Lymphoid Cells Granulocytic Monocytic T cells B cells Neutrophils Basophils Eosinophils Macrophages Kupffer cells Dendritic cells Helper cells Suppressor cells Cytotoxic cells Plasma cells NK cells
- 5. Development of the Immune System ery pl mye neu mφ lym nk thy CD8+ CD4+ CTL TH2 TH1
- 6. Function 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
- 7. Infection and Immunity Balance infection immunity Bolus of infection x virulence immunity Disease =
- 8. • Beneficial: • Protection from Invaders • Elimination of Altered Self • Detrimental: • Discomfort and collateral damage (inflammation) • Damage to self (hypersensitivity or autoimmunity) Effects of the Immune System
- 9. Overview of the Immune System Immune System Innate (Nonspecific) Adaptive (Specific) Cellular Components Humoral Components Cellular Components Humoral Components
- 10. 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
- 11. Anatomical Barriers - Mechanical Factors System or Organ Cell type Mechanism Skin Squamous epithelium Physical barrier Desquamation Mucous Membranes Non-ciliated epithelium (e.g. GI tract) Peristalsis Ciliated epithelium (e.g. respiratory tract) Mucociliary elevator Epithelium (e.g. nasopharynx) Flushing action of tears, saliva, mucus, urine
- 12. Anatomical Barriers - Chemical Factors System or Organ Component Mechanism Skin Sweat Anti-microbial fatty acids Mucous Membranes HCl (parietal cells) Tears and saliva Low pH Lysozyme and phospholipase A Defensins (respiratory & GI tract) Antimicrobial Sufactants (lung) Opsonin
- 13. Anatomical Barriers - Biological Factors System or Organ Component Mechanism Skin and mucous membranes Normal flora Antimicrobial substances Competition for nutrients and colonization
- 14. Humoral Components Component Mechanism Complement Lysis of bacteria and some viruses Opsonin Increase in vascular permeability Recruitment and activation of phagocytic cells Coagulation system Increase vascular permeability Recruitment of phagocytic cells Β-lysin from platelets – a cationic detergent Lactoferrin and transferrin Compete with bacteria for iron Lysozyme Breaks down bacterial cell walls Cytokines Various effects
- 15. Cellular Components Cell Functions Neutrophils Phagocytosis and intracellular killing Inflammation and tissue damage Macrophages Phagocytosis and intracellular killing Extracellular killing of infected or altered self targets Tissue repair Antigen presentation for specific immune response NK and LAK cells Killing of virus-infected and altered self targets Eosinophils Killing of certain parasites
- 17. • Characteristic nucleus, cytoplasm • Granules • CD 66 membrane marker Phagocytes - Neutrophils (PNMs) Blood film showing a monocyte (left) and two neutrophils © Bristol Biomedical Image Archive Used with permission
- 18. primary granules contain cationic proteins, lysozyme, defensins, elastase and myeloperoxidase secondary granules contain lysozyme, NADPH oxidase components, lactoferrin and B12-binding protein azurophilic; characteristic of young neutrophils; specific for mature neutrophils Characteristics of Neutrophil Granules
- 19. Phagocytes - Macrophages • Characteristic nucleus • Lysosomes • CD14 membrane marker Large Lymphocyte, giemsa stained peripheral blood film © Dr Peter Darben, Queensland University of Technology clinical parasitology collection. Used with permission
- 20. Phagocyte Response to Infection • The SOS 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
- 21. Attachment via Receptors: IgG FcR ScavengerR Complement R Toll-like R Initiation of Phagocytosis
- 22. Phagocytosis • Attachment •Pseudopod extension •Phagosome formation •Granule fusion •Phagolysosome formation
- 23. Toxic compounds – Superoxide anion (O2 -), Hydrogen peroxide (H2O2), Singlet oxygen (1O2) and Hydroxyl radical (OH*) Respiratory Burst Oxygen-Dependent Myeloperoxidase-Independent Reactions Pentose-P + NADPH G-6-P-dehydrogenase Glucose +NADP+ NADPH oxidase Cytochrome b558 NADP+ + O2 - NADPH + O2 Superoxide dismutase H2O2 + 1O2 2O2 - + 2H+ 2O2 - + H2O2 OH* + OH - + 1O2
- 24. Respiratory Burst Oxygen-Dependent Myeloperoxidase-Dependent Reactions myeloperoxidase OCl - + H2O H2O2 + Cl - 2OCl - + H2O 1O2 + Cl - + H2O Toxic compounds – Hypochlorous acid (OCl-), and Singlet oxygen (1O2)
- 25. Respiratory Burst Detoxification Reactions H2O2 + O2 Superoxide dismutase H2O + O2 Catalase 2O2 - + 2H+ 2 H2O2
- 26. Oxygen-Independent Killing in the Phagolysosome Effector Molecule Function Cationic proteins (cathepsin) Damage to microbial membranes Lysozyme Hydrolyses mucopeptides in the cell wall Lactoferrin Deprives pathogens of iron Hydrolytic enzymes (proteases) Digests killed organisms
- 27. Summary of Intracellular Killing Pathways Intracellular Killing Oxygen Dependent Oxygen Independent Myleoperoxidase Dependent Myleoperoxidase Independent
- 28. Nitric Oxide Dependent Killing TNF TNF Nitric Oxide Nitric Oxide
- 29. Non-specific Killer Cells NK and LAK cells ADCC (K) cell Activated macrophages Eosinophils They all kill foreign and altered self targets
- 30. 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
- 31. Lymphokine Activated Killer (LAK) cell kills malignant cells kills transformed and malignant cells
- 32. Regulation of NK Cell Function •MHC I •KIR •KAR •KAL •No Killing •Killing
- 33. K Cells morphologically undefined mediate ADCC have Fc receptor recognize antibody coated targets could be NK cells (IgG), macrophages (IgG), eosinophils (IgE) or other cells (IgG)
- 34. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Basic immunology Investigation strategies and methods May 2007
- 35. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Definitions • Immune system = cells, tissues, and molecules that mediate resistance to infections • Immunology = study of structure and function of the immune system • Immunity = resistance of a host to pathogens and their toxic effects • Immune response = collective and coordinated response to the introduction of foreign substances in an individual mediated by the cells and molecules of the immune system
- 36. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Role of the immune system • Defense against microbes • Defense against the growth of tumor cells • kills the growth of tumor cells • Homeostasis • destruction of abnormal or dead cells (e.g. dead red or white blood cells, antigen-antibody complex)
- 37. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Immune System 1. Organs 2. Cells 3. Molecules
- 38. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Immune System: (1) organs • Tonsils and adenoids • Thymus • Lymph nodes • Spleen • Payer’s patches • Appendix • Lymphatic vessels • Bone marrow
- 39. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Immune system: (2) cells • Lymphocytes • T-lymphocytes • B-Lymphocytes, plasma cells • natural killer lymphocytes • Monocytes, Macrophage • Granulocytes • neutrophils • eosinophils • basophils
- 40. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Immune system: (3) molecules • Antibodies • Complement • Cytokines • Interleukines • Interferons
- 41. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Two types of immunity 1. Innate (non-adaptive) • first line of immune response • relies on mechanisms that exist before infection 2. Acquired (adaptive) • Second line of response (if innate fails) • relies on mechanisms that adapt after infection • handled by T- and B- lymphocytes • one cell determines one antigenic determinant
- 42. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Innate immunity • Based on genetic make-up • Relies on already formed components • Rapid response: within minutes of infection • Not specific • same molecules / cells respond to a range of pathogens • Has no memory • same response after repeated exposure • Does not lead to clonal expansion
- 43. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Innate immunity: mechanisms • Mechanical barriers / surface secretion • skin, acidic pH in stomach, cilia • Humoral mechanisms • lysozymes, basic proteins, complement, interferons • Cellular defense mechanisms • natural killer cells neutrophils, macrophages,, mast cells, basophils, eosinophils Neutrophil NK Cell Monocyte Macrophage Basophils & Mast cells Eosinophils
- 44. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Adaptive immunity: second line of response • Based upon resistance acquired during life • Relies on genetic events and cellular growth • Responds more slowly, over few days • Is specific • each cell responds to a single epitope on an antigen • Has anamnestic memory • repeated exposure leads to faster, stronger response • Leads to clonal expansion
- 45. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Adaptive Immunity: active and passive Active Immunity Passive Immunity Natural clinical, sub-clinical infection via breast milk, placenta Artificial Vaccination: Live, killed, purified antigen vaccine immune serum, immune cells
- 46. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Adaptive immunity: mechanisms • Cell-mediated immune response (CMIR) • T-lymphocytes • eliminate intracellular microbes that survive within phagocytes or other infected cells • Humoral immune response (HIR) • B-lymphocytes • mediated by antibodies • eliminate extra-cellular microbes and their toxins Plasma cell (Derived from B-lymphocyte, produces antibodies)
- 47. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Cell-mediated immune response 1. T-cell • recognizes peptide antigen on macrophage in association with major histo-compatibility complex (MHC) class • identifies molecules on cell surfaces • helps body distinguish self from non-self 2. T-cell goes into effectors cells stage that is able to kill infected cells
- 48. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists T lymphocytes 2 types • helper T- lymphocytes (CD4+) • CD4+ T cells activate phagocytes to kill microbes • cytolytic T-lymphocyte (CD8+) • CD8+ T cells destroy infected cells containing microbes or microbial proteins
- 49. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Cell mediated immune response Primary response • production of specific clones of effector T cells and memory clones • develops in several days • does not limit the infection Secondary response • more pronounced, faster • more effective at limiting the infection Example - cytotoxic reactions against intracellular parasites, delayed hypersensitivity (e.g., Tuberculin test) and allograft rejection
- 50. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Humoral immune response 1. B lymphocytes recognize specific antigens • proliferate and differentiate into antibody-secreting plasma cells 2. Antibodies bind to specific antigens on microbes; destroy microbes via specific mechanisms 3. Some B lymphocytes evolve into the resting state - memory cells
- 51. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Antibodies (immunoglobulins) •Belong to the gamma-globulin fraction of serum proteins •Y-shaped or T-shaped polypeptides • 2 identical heavy chains • 2 identical light chains • All immunoglobulins are not antibodies •Five kinds of antibodies • IgG, IgM, IgA, IgD, IgE
- 52. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists IgG • 70-75% of total immuniglobulin • Secreted in high quantities in secondary exposures • Cross the placenta • Major functions / applications • neutralize microbes and toxins • opsonize antigens for phagocytosis • activate the complement • protect the newborn • 4-fold rise or fall indicates active infection • A single positive sample indicates past exposure
- 53. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists IgM • Secreted initially during primary infection • Cannot cross the placenta • Major functions / applications • secreted first during primary exposure • activates the complement • used as a marker of recent infection •Presence in newborn means infection •Single positive sample in serum or CSF indicates recent or active infection •Used to detect early phase of infection
- 54. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists IgA • Monomeric in serum • Dimeric with secretory component in the lumen of the gastro-intestinal tract and in the respiratory tract • Major function / application • neutralizes microbes and toxins •Sero-diagnosis of tuberculosis •Synthicial respiratory virus tests
- 55. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists IgD • Monomeric • Major functions / applications • present on the surface of B lymphocytes • functions as membrane receptor • role unclear • has a role in antigen stimulated lymphocyte differentiation
- 56. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Serodiagnosis of infectious and non infectious allergies (e.g., allergic bronchopulmonary aspergillosis, parasitic diseases) IgE • Mediates type I hypersensitivity • Monomeric • Major functions / applications • associated with anaphylaxis • plays a role in immunity to helminthic parasites
- 57. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Sequential IgM-IgG humoral response •IgM • produced as a first response to many antigens • levels remain high transiently •IgG • produced after IgM • higher levels persist in small amounts throughout life • produced in large amounts during secondary response • persistence of antigen sensitive ‘memory cells’ after primary response
- 58. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists IgM – IgG sequential response First stimulus Time Second stimulus Antibody titer IgM IgG Anamnestic response
- 59. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Failure of immune response • Immune response helps individuals defend against • microbes • some cancers • Immune response can fail • hypersensitivity reactions • immunodeficiency
- 60. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Hypersensitivity reactions • Cause cell damage through excessive immune response to antigens • Hypersensitivity • overreaction to infectious agents • Allergy • overreaction to environmental substances • Autoimmunity • overreaction to self
- 61. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Immunodeficiency • Loss or inadequate function of various components of the immune system • Can occur in any part or state of the immune system • physical barrier, phagocytes, B lymphocytes, T lymphocytes, complement, natural killer cells • The immuno-compromised host • has an impaired function of immune system • is at high risk of infection
- 62. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Immunodeficiency • Congenital (primary) immunodeficiency • genetic abnormality • defect in lymphocyte maturation • Acquired (secondary) immunodeficiency • results from infections, nutritional deficiencies or treatments • AIDS, chronic leukemia
- 63. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Altered immunity: immuno-compromised Disorder Compromised function Altered anatomic barrier Mucus membrane Reduction in IgA Microbe binding Gastro-intestinal tract Elevated pH Bacteria killing Change in flora Colonization resistance Immune system Innate immunity Reduction of complement Activates phagocytosis Opsonization of bacteria Membrane attack complex Neutropenia Monocytopenia Phagocytosis Bacteria killing Adaptive immunity Reduction of T cells Activation of macrophages Activation of B lymphocytes Hypo-gammaglobulinemia Neutralizes pathogens and toxins, opsonization, complement activation
- 64. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Summary (1) • Innate immunity • relies on mechanisms already existing before microbe infects host • is the first line of defense • has no memory for subsequent exposure • relies on non specific mechanisms
- 65. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Summary (2) • Adaptive immunity • develops following entry of microbe into the host • comes into action after innate immunity fails to get rid of microbe • has memory to deal with subsequent exposure • happens through specific cells • T cells (cell mediated) • B cells (antibody mediated)
- 66. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Summary (3) • Primary immune response • short lasting • smaller in magnitude • Secondary immune response • longer in duration • larger in magnitude • develop ‘memory cells’ following primary response • Failure of immune response can result in: • hypersensitivity • immunodeficiency
- 67. E P I D E M I C A L E R T A N D R E S P O N S E Laboratory Training for Field Epidemiologists Developed by the Department of Epidemic and Pandemic Alert and Response of the World Health Organization with assistance from: European Program for Intervention Epidemiology Training Canadian Field Epidemiology Program Thailand Ministry of Health Institut Pasteur Investigation strategies and methods
- 68. Overview of the Immune System Chapter 1
- 69. Immunology • The Study Of Immune System • Latin Word immunis=“exempt” • Earliest Written Reference was Thucydides 430 BC • Pasteur Was First To Successfully Apply Vaccination
- 70. Pasteur Observing Rabies Vaccination
- 71. Humoral Or Cellular Immunity? • Pasteur Did Not Know How Vaccination Worked • Behring and Kitasato (1890) Proposed Serum Was Responsible For Immunity • Elvin Kabat (1930), gamma-globulin, Antibody • Antibodies Were Present in Body Fluids=Humor • Therefore: Humoral Immunity
- 72. Innate (Non-Specific) Immunity • Innate Immunity Made Up Of 4 Forms • Anatomical, physiological, phagocytic and inflammatory • Anatomical: skin, epidermis (densely packed dead cells) • Flow of Mucus Prevents Bacterial Entry By Washing Them Away • Normal Flora Colonize Epithelial Cells Of Mucosal Surfaces, Pathogens Compete With Them For Attachment Sites
- 73. Cell Mediated Immunity • In 1883 Ellie Metchnikoff Showed That Cells Responsible For Immune State • Phagocytes More Active In Immune Animals • She Hypothesized That Cells Responsible For Immunity, Not Serum Components • Controversy Developed But Humoral School Prevailed Till 1940 • Merrill Chase Expt (1940) with Tuberculosis Infected Animals, Immunity Thru White Blood Cell Transfers
- 74. • Physiologic Barriers – pH (stomach) – Temperature (fever) – Soluble Factors (interferons, lysozyme) • Phagocytic Barriers – Specialized Cells Perform Most Of Phagocytosis (macrophages, neutrophils) Innate (Non-Specific) Immunity
- 75. • Inflammatory Barriers – Vasodilation – Cappillary permeability – Leukocyte Infiltration • Chemotactic means • Increased Adherence • Leaky capillaries Innate (Non-Specific) Immunity
- 76. E-coli Adhering to Urinary Epithelial Cells
- 77. • C-Reactive Protein (liver) • Histamine (vasodilation, increased permeability • Kinins – Small peptides normally inactive in blood – Ex. Bradykinin (causes pain) Chemical Mediators Of Inflammation
- 78. • Close collaboration – Macrophages can secret cytokines that affect the type of adaptive immunity • Macrophages/DCs Present Antigen • Lymphocytes Increase Effectiveness of Macrophages Innate and Adaptive Immunity Collaborate
- 79. • 4 Characteristics – Memory – Diversity – Antigenic Specificity – Self/nonself recognition Adaptive Immunity
- 80. ~ 60% neutrophils (50% - 70%) ~ 3% eosinophils (>0% - 5%) ~ 0.5% basophils (>0% - 2%) ~ 5% monocytes (1% - 9%) ~ 30% lymphocytes (20% - 40%) Cell Frequency of Different Leukocytes in Healthy Individuals
- 84. • Lymphocytes – B cells, mature in Bone Marrow (CD19, CD20) • in periphery they express a unique surface antibody • Plasma cells differentiated B cell, short lifespan, antibody factory • Memory B cell (CD45RO), long life span Cells Of The Immune System
- 85. • T cells, mature in Thymus (CD3, CD4, CD8) • Two Major subsets, TH (CD4) and TC (CD8) • Third type TS not as clear • Mature T cell expresses TCR • TCR cannot recognize antigen on its own • MHC I (all nucleated cells) or MHC II (APCs) is required • TH cells secrete cytokines • TC less cytokines, more cytotoxic (virus and tumor survailance) Cells Of Immune System
- 86. • Antigen Presenting Cells • Number of Cells capable of Antigen Presentation • Dendritic Cell (DC) professional APC • Macrophages, B cells • Besides Antigen They Provide Co- stimulation • APCs are a safeguard against autoimmunity Cells Of Immune System
- 88. APC INTERACTING WITH T CELL
- 89. • B cells are specific, 100,000 identical antibodies on 1 B cell • 108 different B Cells in Bone Marrow, Enormous Diversity • Reduction To Avoid Auto-antibodies • Same for T Cells, Elimination in Thymus Specificity and Diversity
- 90. • Genetic Complex With Multiple Loci • MHC I - CTLs • MHC II - TH • MHC I+2-microglobulin – 3 classes A, B, C (human) – 2 classes K and D (mouse) • MHC II – 3 classes DP, DQ, DR (human) – 2 classes IA, IE (mouse) • Highly Polymorphic in Humans Major Histocompatibility Complex (MHC)
- 92. • First Protein Antigens Must Be Broken Down • Form Complexes With MHC I or II • Exogenous Antigens – Antigens Processed Thru Endocytic Pathway – Binding of Ags To MHC II – Expression of MHC II+Ags On Surface – CD4 T Cells Recognize Ag Thru Class II MHC • Endogenous Antigens – Antigens Processed Thru Cytosolic Pathway – Produced Within Cell, Ex. Virus Ag, Cancer Ag – MHC I Molecules Bind Ag in ER – CD8 T Cells Recognize Ag Thru MHC I Processing and Presentation of Antigens
- 93. Processing and Presentation of Antigens
- 94. • Ag Reactivity Determines Clonal Expansion • Immunologic Memory is By-product of Clonal Expansion • Humoral Primary Response – 7 Days Before Antibody Levels Rise – Antibody Titer is Low Compared to Secondary • Humoral Secondary Response – 1-2 Days Antibodies Are Detected – Antibody Titer Higher (100-1000 fold higher) – Lasts Longer Clonal Selection of Lymphocytes and Memory
- 96. • Cell Mediated Response (TH or CTL) is Similar – Primary Response 10-14 Days For Skin Rejection – Secondary Response Starts Immediately Clonal Selection of Lymphocytes and Memory
- 97. Aberrant Respones – Allergy, Asthma, Anaphylaxis ➢Asthma/Allergies Attacks Are Very Common ➢Mediated Thru IgE ➢IgE Binds Mast Cells, Basophils ➢Re-exposure Cross Links IgE ➢Causes Degranulation, Histamine, prostanoids