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Cell mediated and antibody mediated immunity by waqar ahmed baber
- 1. Hafiz Waqar AhmedBaber 560-FBAS/BSBT/S14 Department of Biotechnology Faculty of Basic and applied sciences
- 2. Cell mediated and Antibodymediated immunity
- 3. Antigens Antigens have2 characteristics Immunogenicity: Ability to provoke immune response Reactivity:Ability of antigen to react specifically with antibodies it provoked Entire microbes may act as antigen Typically, just certain small parts of large antigen molecule triggers response (epitope or antigenic determinant)
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- 5. Cellular Immunity Tcells attack foreign cells and diseased host cells; memory of Ag Three classes of T cells 1. Cytotoxic T cells (Tc cells) carry out attack 2. Helper T cells: help promote Tc cell and B cell action and nonspecific defense mechanisms 3. Memory T cells: provide immunity from future exposure to antigen
- 6. MHC Proteins Membrane glycoproteins,bind to antigens, encoded by chromosome 6, form MHC. 2 Classes of MHC Proteins Class I: found in membranes of all nucleated cells Pick up small peptides in cell and carry them to the surface: T cells ignore normal peptides abnormal peptides or viral proteins activate T cells to destroy cell Class II: found in membranes of antigen- presenting cells (APCs) found in lymphocytes Antigenic fragments
- 7. Antigens and MHCProteins Figure 22–16a (Navigator)
- 8. Antigen-Presenting Cells (APCs) Responsible for activating T cells against foreign cells and proteins Phagocytic APCs : Free and fixed macrophages: in connective tissues Kupffer cells: of the liver Microglia: in the CNS
- 9. Pinocytic APCs Langerhanscells: in the skin Dendritic cells: in lymph nodes and spleen
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- 11. Mechanism of Tcell recognition and activation
- 12. Antigen Recognition InactiveT cell receptors: recognize Class I or Class II MHC proteins recognize a specific antigen Binding occurs when MHC protein matches antigen
- 13. TC cell Recognition Antigen presentation MHC-I proteins found on nearly all nucleated body cells display peptides produced by host cells TC cell activation 1. binding of cytotoxic T cells (CD8 cells) to abnormal peptides on MHC-I and 2. costimulation via a cytokine triggers clonal selection: clone of identical T cells against cells with same epitope
- 14. TH cell Recognition Antigen presentation role of MHC-II proteins found only on antigen presenting cells display only foreign antigens stimulate helper T cells (CD4 cells)
- 15. CD Markers Alsocalled cluster of differentiation markers: in T cell membranes molecular mechanism of antigen recognition more than 70 types: designated by an identifying number CD3 Receptor Complex Found in all T cells
- 16. CD8 Markers Foundon cytotoxic T cells and suppressor T cells Respond to antigens on Class I MHC proteins CD4 Markers Found on helper T cells Respond to antigens on Class II MHC proteins CD8 or CD4 Markers - Bind to CD3 receptor complex Prepare cell for activation
- 17. Costimulation For Tcell to be activated, it must be costimulated: by binding to stimulating cell at second site which confirms the first signal
- 18. 2 Classes ofCD8 T Cells Activated by exposure to antigens on MHC proteins: one responds quickly: producing cytotoxic T cells and memory T cells the other responds slowly: producing suppressor T cells
- 19. TH cell Activation 1.binding of helper T cells (CD4 cells) to epitope displayed on MHC-II of APC 2. costimulation via a cytokine 3. triggers clonal selection
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- 21. Activation of HelperT Cells Figure 22–18 Helper T Cells - Activated CD4 T cells divide into: active helper T cells: secrete cytokines memory T cells: remain in reserve
- 22. Attack Phase: Roleof Helper T Cells Secretes interleukins attract neutrophils, NK cells, macrophages stimulate phagocytosis stimulate T and B cell mitosis and maturation Coordinate humoral and cellular immunity
- 23. Figure 22–17 (Navigator) Activationof Cytotoxic T Cells Also called killer T cells Seek out and immediatel y destroy target cells
- 24. Actions of CytotoxicT Cells 1. Release perforin: to destroy antigenic cell membrane 2. Secrete poisonous lymphotoxin: to destroy target cell 3. Activate genes in target cell: that cause cell to die
- 25. Slow Response Cantake up to 2 days from time of first exposure to an antigen, for cytotoxic T cells to reach effective levels
- 26. Memory Tc Cells Produced with cytotoxic T cells Stay in circulation Immediately form cytotoxic T cells: if same antigen appears again
- 27. Suppressor T Cells Secrete suppression factors Inhibit responses of T and B cells After initial immune response Limit immune reaction to single stimulus
- 28. 4 Functions ofCytokines 1. Stimulate T cell divisions: produce memory T cells accelerate cytotoxic T cell maturation 2. Attract and stimulate macrophages 3. Attract and stimulate NK cells 4. Promote activation of B cells
- 29. Figure 22–19 Pathways ofT Cell Activation
- 30. Humoral Immunity Recognition B cell receptors bind antigen, take in and digest antigen then display epitopes on its MHC-II protein After costimulation by TH cell, divide repeatedly, differentiate into plasma cells, produce antibodies specific to that antigen Attack antibodies bind to antigen, render it harmless, ‘tag it’ for destruction Memory some B cells differentiate into memory cells
- 31. Humoral Immunity -Recognition 21- 31
- 32. B Cells Responsiblefor antibody-mediated immunity Attack antigens by producing specific antibodies Millions of populations, each with different antibody molecules Sensitization Corresponding antigens in interstitial fluids bind to B cell receptors B cell prepares for activation Preparation process is sensitization
- 33. Figure 22–20 (Navigator) BCell Sensitization and Activation During sensitization, antigens are taken into the B cell, processed, reappear on surface, bound to Class II MHC protein
- 34. Helper T Cells Sensitized B cell is prepared for activation, but needs helper T cell activated by same antigen B Cell Activation Helper T cell binds to MHC complex: secretes cytokines that promote B cell activation and division
- 35. B Cell Division Activated B cell divides into: plasma cells -Synthesize and secrete antibodies into interstitial fluid Memory B cells-Like memory T cells remain in reserve to respond to next infection
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