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  • 1. Specific Host Defenses: TheSpecific Host Defenses: TheImmune ResponseImmune Response
  • 2. The Immune ResponseThe Immune ResponseImmunityImmunity: “Free from burden”. Ability of: “Free from burden”. Ability ofan organism to recognize and defend itselfan organism to recognize and defend itselfagainstagainst specificspecific pathogens or antigens.pathogens or antigens.Immune ResponseImmune Response: Third line of defense.: Third line of defense.Involves production of antibodies andInvolves production of antibodies andgeneration of specialized lymphocytesgeneration of specialized lymphocytesagainst specific antigens.against specific antigens.AntigenAntigen: Molecules from a pathogen or: Molecules from a pathogen orforeign organism that provoke a specificforeign organism that provoke a specificimmune response.immune response.
  • 3. The Immune System is the Third Lineof Defense Against Infection
  • 4. Innate or Genetic ImmunityInnate or Genetic Immunity: Immunity an: Immunity anorganism is born with.organism is born with.Genetically determined.Genetically determined.May be due to lack of receptors or otherMay be due to lack of receptors or othermolecules required for infection.molecules required for infection.Innate human immunity to canine distemper.Innate human immunity to canine distemper.Immunity of mice to poliovirus.Immunity of mice to poliovirus.Acquired ImmunityAcquired Immunity:Immunity that an:Immunity that anorganismorganism developsdevelops during lifetime.during lifetime.Not genetically determined.Not genetically determined.May be acquired naturally or artificially.May be acquired naturally or artificially.Development of immunity to measles in response toDevelopment of immunity to measles in response toinfection or vaccination.infection or vaccination.
  • 5. Components of Human Immune System
  • 6. Types of Acquired ImmunityTypes of Acquired ImmunityI. Naturally Acquired ImmunityI. Naturally Acquired Immunity: Obtained in: Obtained inthe course of daily life.the course of daily life.A. Naturally Acquired Active ImmunityA. Naturally Acquired Active Immunity::AntigensAntigens or pathogens enter body naturally.or pathogens enter body naturally.Body generates an immune response to antigens.Body generates an immune response to antigens.Immunity may be lifelong (chickenpox or mumps)Immunity may be lifelong (chickenpox or mumps)or temporary (influenza or intestinal infections).or temporary (influenza or intestinal infections).B. Naturally Acquired Passive ImmunityB. Naturally Acquired Passive Immunity::AntibodiesAntibodies pass from mother to fetus via placentapass from mother to fetus via placentaor breast feeding (or breast feeding (colostrumcolostrum).).No immune response to antigens.No immune response to antigens.Immunity is usuallyImmunity is usually short-livedshort-lived (weeks to months).(weeks to months).Protection until child’s immune system develops.Protection until child’s immune system develops.
  • 7. Types of Acquired Immunity (Continued)Types of Acquired Immunity (Continued)II. Artificially Acquired ImmunityII. Artificially Acquired Immunity: Obtained by: Obtained byreceiving a vaccine or immune serum.receiving a vaccine or immune serum.1. Artificially Acquired Active Immunity1. Artificially Acquired Active Immunity::AntigensAntigens are introduced in vaccines (are introduced in vaccines (immunizationimmunization).).Body generates an immune response to antigens.Body generates an immune response to antigens.Immunity can be lifelong (oral polio vaccine) or temporaryImmunity can be lifelong (oral polio vaccine) or temporary(tetanus toxoid).(tetanus toxoid).2. Artificially Acquired Passive Immunity2. Artificially Acquired Passive Immunity::PreformedPreformed antibodiesantibodies ((antiserumantiserum) are introduced into body) are introduced into bodyby injection.by injection.Snake antivenom injection from horses or rabbits.Snake antivenom injection from horses or rabbits.Immunity is short lived (half life three weeks).Immunity is short lived (half life three weeks).Host immune system does not respond to antigens.Host immune system does not respond to antigens.
  • 8. SerumSerum: Fluid that remains after blood has clotted: Fluid that remains after blood has clottedand cells have been removed.and cells have been removed.AntiserumAntiserum: Serum containing antibodies to a: Serum containing antibodies to aspecific antigen(s). Obtained from injecting anspecific antigen(s). Obtained from injecting ananimal (horse, rabbit, goat) with antigen (snakeanimal (horse, rabbit, goat) with antigen (snakevenom, botulism or diphtheria toxin).venom, botulism or diphtheria toxin).SerologySerology: The study of reactions between: The study of reactions betweenantibodies and antigens.antibodies and antigens.Gamma GlobulinsGamma Globulins: Fraction of serum that: Fraction of serum thatcontains most of the antibodies.contains most of the antibodies.Serum SicknessSerum Sickness: Disease caused by multiple: Disease caused by multipleinjections of antiserum. Immune response toinjections of antiserum. Immune response toforeign proteins. May cause fever, kidneyforeign proteins. May cause fever, kidneyproblems, and joint pain. Rare today.problems, and joint pain. Rare today.
  • 9. Duality of Immune SystemDuality of Immune SystemI. Humoral (Antibody-Mediated) ImmunityI. Humoral (Antibody-Mediated) ImmunityInvolves production of antibodies against foreignInvolves production of antibodies against foreignantigens.antigens.Antibodies are produced by a subset of lymphocytesAntibodies are produced by a subset of lymphocytescalledcalled B cellsB cells..B cells that are stimulated will actively secreteB cells that are stimulated will actively secreteantibodies and are calledantibodies and are called plasma cellsplasma cells..Antibodies are found inAntibodies are found in extracellular fluidsextracellular fluids (blood(bloodplasma, lymph, mucus, etc.) and the surface of B cells.plasma, lymph, mucus, etc.) and the surface of B cells.Defense against bacteria, bacterial toxins, and virusesDefense against bacteria, bacterial toxins, and virusesthat circulate freely in body fluids,that circulate freely in body fluids, beforebefore they enterthey entercells.cells.Also cause certain reactions against transplantedAlso cause certain reactions against transplantedtissue.tissue.
  • 10. Antibodies are Produced by B Lymphocytes
  • 11. Antibodies are Proteins that Recognize Specific Antigens
  • 12. Duality of Immune System (Continued)Duality of Immune System (Continued)II. Cell Mediated ImmunityII. Cell Mediated ImmunityInvolves specialized set of lymphocytes calledInvolves specialized set of lymphocytes called T cellsT cellsthat recognize foreign antigens on the surface of cells,that recognize foreign antigens on the surface of cells,organisms, or tissues:organisms, or tissues:Helper T cellsHelper T cellsCytotoxic T cellsCytotoxic T cellsT cellsT cells regulateregulate proliferation and activity of other cellsproliferation and activity of other cellsof the immune system: B cells, macrophages,of the immune system: B cells, macrophages,neutrophils, etc.neutrophils, etc.Defense against:Defense against:Bacteria and viruses that are inside host cells and areBacteria and viruses that are inside host cells and areinaccessible to antibodies.inaccessible to antibodies.Fungi, protozoa, and helminthsFungi, protozoa, and helminthsCancer cellsCancer cellsTransplanted tissueTransplanted tissue
  • 13. Cell Mediated Immunity is Carried Out by T Lymphocytes
  • 14. AntigensAntigensMost areMost are proteinsproteins or largeor large polysaccharidespolysaccharides fromfroma foreign organism.a foreign organism.MicrobesMicrobes: Capsules, cell walls, toxins, viral capsids,: Capsules, cell walls, toxins, viral capsids,flagella, etc.flagella, etc.NonmicrobesNonmicrobes: Pollen, egg white , red blood cell: Pollen, egg white , red blood cellsurface molecules, serum proteins, and surfacesurface molecules, serum proteins, and surfacemolecules from transplanted tissue.molecules from transplanted tissue.Lipids and nucleic acids are only antigenic whenLipids and nucleic acids are only antigenic whencombinedcombined with proteins or polysaccharides.with proteins or polysaccharides.Molecular weight of 10,000 or higher.Molecular weight of 10,000 or higher.HaptenHapten: Small foreign molecule that is not antigenic. Must be: Small foreign molecule that is not antigenic. Must becoupled to acoupled to a carriercarrier molecule to be antigenic. Once antibodiesmolecule to be antigenic. Once antibodiesare formed they will recognize hapten.are formed they will recognize hapten.
  • 15. AntigensAntigensEpitopeEpitope::Small part of an antigen that interactsSmall part of an antigen that interactswith an antibody.with an antibody.Any given antigen may have severalAny given antigen may have severalepitopes.epitopes.Each epitope is recognized by a differentEach epitope is recognized by a differentantibody.antibody.
  • 16. Epitopes: Antigen Regions that Interactwith Antibodies
  • 17. AntibodiesAntibodiesProteinsProteins that recognize and bind to a particularthat recognize and bind to a particularantigen with very highantigen with very high specificityspecificity..Made in response to exposure to the antigen.Made in response to exposure to the antigen.One virus or microbe may have severalOne virus or microbe may have several antigenicantigenicdeterminant sitesdeterminant sites, to which different antibodies, to which different antibodiesmay bind.may bind.Each antibody has at least two identical sitesEach antibody has at least two identical sitesthat bind antigen:that bind antigen: Antigen binding sitesAntigen binding sites..Valence of an antibodyValence of an antibody: Number of antigen: Number of antigenbinding sites. Most arebinding sites. Most are bivalentbivalent..Belong to a group of serum proteins calledBelong to a group of serum proteins calledimmunoglobulins (Igs).immunoglobulins (Igs).
  • 18. Antibody StructureAntibody StructureMonomerMonomer: A flexible Y-shaped molecule with: A flexible Y-shaped molecule withfour protein chains:four protein chains:2 identical2 identical lightlight chainschains2 identical2 identical heavyheavy chainschainsVariable RegionsVariable Regions: Two sections at the end of: Two sections at the end ofY’s arms. Contain theY’s arms. Contain the antigen binding sitesantigen binding sites(Fab)(Fab). Identical on the same antibody, but vary. Identical on the same antibody, but varyfrom one antibody to another.from one antibody to another.Constant RegionsConstant Regions: Stem of monomer and lower: Stem of monomer and lowerparts of Y arms.parts of Y arms.Fc regionFc region: Stem of monomer only. Important: Stem of monomer only. Importantbecause they can bind to complement or cells.because they can bind to complement or cells.
  • 19. Antibody Structure
  • 20. Immunoglobulin ClassesImmunoglobulin ClassesI. IgGI. IgGStructure:Structure: MonomerMonomerPercentage serum antibodies:Percentage serum antibodies: 80%80%Location:Location: Blood, lymph, intestineBlood, lymph, intestineHalf-life in serum:Half-life in serum: 23 days23 daysComplement Fixation:Complement Fixation: YesYesPlacental Transfer:Placental Transfer: YesYesKnown Functions:Known Functions: Enhances phagocytosis,Enhances phagocytosis,neutralizes toxins and viruses, protects fetus andneutralizes toxins and viruses, protects fetus andnewborn.newborn.
  • 21. Immunoglobulin ClassesImmunoglobulin ClassesII. IgMII. IgMStructure:Structure: PentamerPentamerPercentage serum antibodies:Percentage serum antibodies: 5-10%5-10%Location:Location: Blood, lymph, B cell surface (monomer)Blood, lymph, B cell surface (monomer)Half-life in serum:Half-life in serum: 5 days5 daysComplement Fixation:Complement Fixation: YesYesPlacental Transfer:Placental Transfer: NoNoKnown Functions:Known Functions: First antibodies producedFirst antibodies producedduring an infection. Effective against microbes andduring an infection. Effective against microbes andagglutinating antigens.agglutinating antigens.
  • 22. Immunoglobulin ClassesImmunoglobulin ClassesIII. IgAIII. IgAStructure:Structure: DimerDimerPercentage serum antibodies:Percentage serum antibodies: 10-15%10-15%Location:Location: Secretions (tears, saliva, intestine, milk),Secretions (tears, saliva, intestine, milk),blood and lymph.blood and lymph.Half-life in serum:Half-life in serum: 6 days6 daysComplement Fixation:Complement Fixation: NoNoPlacental Transfer:Placental Transfer: NoNoKnown Functions:Known Functions: Localized protection ofLocalized protection of mucosalmucosalsurfaces. Provides immunity to infant digestivesurfaces. Provides immunity to infant digestivetract.tract.
  • 23. Immunoglobulin ClassesImmunoglobulin ClassesIV. IgDIV. IgDStructure:Structure: MonomerMonomerPercentage serum antibodies:Percentage serum antibodies: 0.2%0.2%Location:Location: B-cell surface, blood, and lymphB-cell surface, blood, and lymphHalf-life in serum:Half-life in serum: 3 days3 daysComplement Fixation:Complement Fixation: NoNoPlacental Transfer:Placental Transfer: NoNoKnown Functions:Known Functions: In serum function is unknown.In serum function is unknown.On B cell surface, initiate immune response.On B cell surface, initiate immune response.
  • 24. Immunoglobulin ClassesImmunoglobulin ClassesV. IgEV. IgEStructure:Structure: MonomerMonomerPercentage serum antibodies:Percentage serum antibodies: 0.002%0.002%Location:Location: Bound to mast cells and basophilsBound to mast cells and basophilsthroughout body. Blood.throughout body. Blood.Half-life in serum:Half-life in serum: 2 days2 daysComplement Fixation:Complement Fixation: NoNoPlacental Transfer:Placental Transfer: NoNoKnown Functions:Known Functions: Allergic reactions. PossiblyAllergic reactions. Possiblylysis of worms.lysis of worms.
  • 25. How Do B Cells Produce Antibodies?How Do B Cells Produce Antibodies?B cells develop fromB cells develop from stem cellsstem cells in the bonein the bonemarrow of adults (liver of fetuses).marrow of adults (liver of fetuses).After maturation B cells migrate to lymphoidAfter maturation B cells migrate to lymphoidorgans (lymph node or spleen).organs (lymph node or spleen).Clonal SelectionClonal Selection: When a B cell encounters an: When a B cell encounters anantigen it recognizes, it is stimulated and dividesantigen it recognizes, it is stimulated and dividesinto many clones calledinto many clones called plasma cellsplasma cells, which, whichactively secrete antibodies.actively secrete antibodies.Each B cell produces antibodies that willEach B cell produces antibodies that willrecognize only one antigenic determinant.recognize only one antigenic determinant.
  • 26. Clonal Selection of B Cells is Causedby Antigenic Stimulation
  • 27. Humoral Immunity (Continued)Humoral Immunity (Continued)ApoptosisApoptosisProgrammed cell death (“Falling away”).Programmed cell death (“Falling away”).Human body makes 100 million lymphocytesHuman body makes 100 million lymphocytesevery day. If an equivalent number doesn’t die,every day. If an equivalent number doesn’t die,will develop leukemia.will develop leukemia.B cells that do not encounter stimulating antigenB cells that do not encounter stimulating antigenwill self-destruct and send signals to phagocyteswill self-destruct and send signals to phagocytesto dispose of their remains.to dispose of their remains.Many virus infected cells will undergo apoptosis,Many virus infected cells will undergo apoptosis,to help prevent spread of the infection.to help prevent spread of the infection.
  • 28. Humoral Immunity (Continued)Humoral Immunity (Continued)Clonal SelectionClonal SelectionClonal SelectionClonal Selection: B cells (and T cells) that: B cells (and T cells) thatencounter stimulating antigen will proliferate intoencounter stimulating antigen will proliferate intoa large group of cells.a large group of cells.Why don’t we produce antibodies against ourWhy don’t we produce antibodies against ourown antigens? We have developedown antigens? We have developed tolerancetolerance totothem.them.Clonal DeletionClonal Deletion: B and T cells that react against: B and T cells that react againstselfself antigens appear to be destroyed during fetalantigens appear to be destroyed during fetaldevelopment. Process is poorly understood.development. Process is poorly understood.
  • 29. Consequences of Antigen-Antibody BindingConsequences of Antigen-Antibody BindingAntigen-Antibody ComplexAntigen-Antibody Complex: Formed when an: Formed when anantibody binds to an antigen it recognizes.antibody binds to an antigen it recognizes.AffinityAffinity: A measure of binding strength.: A measure of binding strength.1. Agglutination:1. Agglutination: Antibodies cause antigensAntibodies cause antigens(microbes) to clump together.(microbes) to clump together.IgM (decavalent) is more effective that IgG (bivalent).IgM (decavalent) is more effective that IgG (bivalent).HemagglutinationHemagglutination: Agglutination of red blood cells.: Agglutination of red blood cells.Used to determine ABO blood types and to detectUsed to determine ABO blood types and to detectinfluenza and measles viruses.influenza and measles viruses.2. Opsonization:2. Opsonization: Antigen (microbe) is covered withAntigen (microbe) is covered withantibodies that enhances its ingestion and lysis byantibodies that enhances its ingestion and lysis byphagocytic cells.phagocytic cells.
  • 30. Consequences of Antibody Binding
  • 31. Humoral Immunity (Continued)Humoral Immunity (Continued)3. Neutralization:3. Neutralization: IgG inactivates viruses byIgG inactivates viruses bybinding to their surface and neutralize toxins bybinding to their surface and neutralize toxins byblocking their active sites.blocking their active sites.4. Antibody-dependent cell-mediated cytotoxicity:4. Antibody-dependent cell-mediated cytotoxicity:Used to destroy large organisms (e.g.: worms).Used to destroy large organisms (e.g.: worms).Target organism is coated with antibodies andTarget organism is coated with antibodies andbombarded with chemicals from nonspecificbombarded with chemicals from nonspecificimmune cells.immune cells.5. Complement Activation:5. Complement Activation: Both IgG and IgMBoth IgG and IgMtrigger the complement system which results intrigger the complement system which results incell lysis and inflammation.cell lysis and inflammation.
  • 32. Consequences of Antibody Binding
  • 33. Immunological MemoryImmunological MemoryAntibody Titer:Antibody Titer: The amount of antibody in theThe amount of antibody in theserum.serum.Pattern of Antibody Levels During InfectionPattern of Antibody Levels During InfectionPrimary Response:Primary Response:AfterAfter initialinitial exposure to antigen, no antibodies areexposure to antigen, no antibodies arefound in serum for several days.found in serum for several days.A gradual increase in titer, first of IgM and thenA gradual increase in titer, first of IgM and thenof IgG is observed.of IgG is observed.Most B cells become plasma cells, but some B cellsMost B cells become plasma cells, but some B cellsbecome long livingbecome long living memory cellsmemory cells..Gradual decline of antibodies follows.Gradual decline of antibodies follows.
  • 34. Immunological Memory (Continued)Immunological Memory (Continued)Secondary Response:Secondary Response:Subsequent exposure to the same antigen displaysSubsequent exposure to the same antigen displaysa faster and more intense antibody response.a faster and more intense antibody response.Increased antibody response is due to theIncreased antibody response is due to theexistence of memory cells, which rapidly produceexistence of memory cells, which rapidly produceplasma cells upon antigen stimulation.plasma cells upon antigen stimulation.
  • 35. Antibody Response After Exposure to Antigen
  • 36. T Cells and Cell Mediated ImmunityT Cells and Cell Mediated ImmunityAntigens that stimulate this response are mainlyAntigens that stimulate this response are mainlyintracellularintracellular..Requires constant presence of antigen to remainRequires constant presence of antigen to remaineffective.effective.Unlike humoral immunity, cell mediated immunityUnlike humoral immunity, cell mediated immunityis not transferred to the fetus.is not transferred to the fetus.Cytokines:Cytokines: Chemical messengers of immune cells.Chemical messengers of immune cells.Over 100 have been identified.Over 100 have been identified.Stimulate and/or regulate immune responses.Stimulate and/or regulate immune responses.Interleukins:Interleukins: Communication between WBCs.Communication between WBCs.InterferonsInterferons: Protect against viral infections.: Protect against viral infections.ChemokinesChemokines: Attract WBCs to infected areas.: Attract WBCs to infected areas.
  • 37. T Cells and Cell Mediated ImmunityT Cells and Cell Mediated ImmunityCellular Components of Immunity:Cellular Components of Immunity:T cells are key cellular component of immunity.T cells are key cellular component of immunity.T cells have an antigen receptor that recognizesT cells have an antigen receptor that recognizesand reacts to a specific antigen (and reacts to a specific antigen (T cell receptorT cell receptor).).T cell receptor only recognize antigens combinedT cell receptor only recognize antigens combinedwithwith majormajor histocompatabilityhistocompatability (MHC) proteins(MHC) proteins ononthethe surfacesurface of cells.of cells.MHC Class I: Found on all cells.MHC Class I: Found on all cells.MHC Class II: Found on phagocytes.MHC Class II: Found on phagocytes.Clonal selection increases number of T cells.Clonal selection increases number of T cells.
  • 38. T Cells Only Recognize Antigen Associatedwith MHC Molecules on Cell Surfaces
  • 39. T Cells and Cell Mediated ImmunityT Cells and Cell Mediated ImmunityTypes of T cellsTypes of T cells1. T Helper (T1. T Helper (THH) Cells:) Cells: Central role in immuneCentral role in immuneresponse.response.Most are CD4Most are CD4++Recognize antigen on the surface of antigen presentingRecognize antigen on the surface of antigen presentingcells (e.g.: macrophage).cells (e.g.: macrophage).Activate macrophagesActivate macrophagesInduce formation of cytotoxic T cellsInduce formation of cytotoxic T cellsStimulate B cells to produce antibodies.Stimulate B cells to produce antibodies.
  • 40. Central Role of Helper T Cells
  • 41. Types of T cells (Continued)Types of T cells (Continued)2. Cytotoxic T (Tc) Cells:2. Cytotoxic T (Tc) Cells: Destroy target cells.Destroy target cells.Most are CD4 negative (CD4Most are CD4 negative (CD4--).).Recognize antigens on the surface of all cells:Recognize antigens on the surface of all cells:• Kill host cells that are infected with viruses or bacteria.Kill host cells that are infected with viruses or bacteria.• Recognize and kill cancer cells.Recognize and kill cancer cells.• Recognize and destroy transplanted tissue.Recognize and destroy transplanted tissue.Release protein calledRelease protein called perforinperforin which forms a pore inwhich forms a pore intarget cell, causing lysis of infected cells.target cell, causing lysis of infected cells.UndergoUndergo apoptosisapoptosis when stimulating antigen is gone.when stimulating antigen is gone.
  • 42. Cytotoxic T Cells Lyse Infected Cells
  • 43. Types of T cells (Continued)Types of T cells (Continued)3. Delayed Hypersensitivity T (T3. Delayed Hypersensitivity T (TDD) Cells:) Cells: Mostly TMostly Thelper and a few cytotoxic T cells that arehelper and a few cytotoxic T cells that areinvolved in some allergic reactions (poison ivy)involved in some allergic reactions (poison ivy)and rejection of transplanted tissue.and rejection of transplanted tissue.4. T Suppressor (Ts) Cells:4. T Suppressor (Ts) Cells: May shut downMay shut downimmune response.immune response.
  • 44. Nonspecific Cellular ComponentsNonspecific Cellular Components1. Activated Macrophages:1. Activated Macrophages: Stimulated phagocytes.Stimulated phagocytes.Stimulated by ingestion of antigenStimulated by ingestion of antigenLarger and more effective phagocytes.Larger and more effective phagocytes.Enhanced ability to eliminate intracellular bacteria,Enhanced ability to eliminate intracellular bacteria,virus-infected and cancerous cells.virus-infected and cancerous cells.2. Natural Killer (NK) Cells:2. Natural Killer (NK) Cells:Lymphocytes that destroy virus infected and tumorLymphocytes that destroy virus infected and tumorcells.cells.Not specific. Don’t require antigen stimulation.Not specific. Don’t require antigen stimulation.Not phagocytic, but must contact cell in order to lyse it.Not phagocytic, but must contact cell in order to lyse it.
  • 45. Relationship Between Cell-MediatedRelationship Between Cell-Mediatedand Humoral Immunityand Humoral Immunity1. Antibody Production1. Antibody ProductionT-Dependent Antigens:T-Dependent Antigens:Antibody production requires assistance from T helper cells.Antibody production requires assistance from T helper cells.A macrophage cells ingest antigen and presents it to TA macrophage cells ingest antigen and presents it to THH cell.cell.TTHH cell stimulates B cells specific for antigen to become plasmacell stimulates B cells specific for antigen to become plasmacells.cells.Antigens are mainly proteins on viruses, bacteria, foreign redAntigens are mainly proteins on viruses, bacteria, foreign redblood cells, and hapten-carrier molecules.blood cells, and hapten-carrier molecules.T-Independent Antigens:T-Independent Antigens:Antibody production does not require assistance from T cells.Antibody production does not require assistance from T cells.Antigens are mainly polysaccharides or lipopolysaccharides withAntigens are mainly polysaccharides or lipopolysaccharides withrepeating subunits (bacterial capsules).repeating subunits (bacterial capsules).Weaker immune response than for T-dependent antigens.Weaker immune response than for T-dependent antigens.
  • 46. Humoral Response to T Dependent Antigens
  • 47. Humoral Response to T Dependent Antigens
  • 48. Relationship Between Cell-MediatedRelationship Between Cell-Mediatedand Humoral Immunityand Humoral Immunity2. Antibody Dependent Cell Mediated2. Antibody Dependent Cell MediatedCytotoxicityCytotoxicityTarget cell is covered with antibodies, leaving FcTarget cell is covered with antibodies, leaving Fcportion sticking outwards.portion sticking outwards.Natural killer and other nonspecific cells that haveNatural killer and other nonspecific cells that havereceptors for Fc region are stimulated to kill targetedreceptors for Fc region are stimulated to kill targetedcells.cells.Target organism is lysed by substances secreted byTarget organism is lysed by substances secreted byattacking cells.attacking cells.Used to destroy large organisms that cannot beUsed to destroy large organisms that cannot bephagocytosed.phagocytosed.
  • 49. Destruction of Large Parasites by ADCC
  • 50. Overview of the Immune Response