Cell Mediated Immunity - Dr. Hussein - 5th PPT PDF

CELL MEDIATED IMMUNITY - DR. HUSSEIN (5TH PPT) 1. What activates T lymphocytes in cell-mediated immunity? A: Cell-associated microbes. 2. What are the phases of T cell responses? A: Antigen recognition, costimulation, cytokine secretion, clonal expansion, and differentiation. 3. What role do ad...

CELL MEDIATED IMMUNITY - DR. HUSSEIN (5TH PPT) 1. What activates T lymphocytes in cell-mediated immunity? A: Cell-associated microbes. 2. What are the phases of T cell responses? A: Antigen recognition, costimulation, cytokine secretion, clonal expansion, and differentiation. 3. What role do adhesion molecules play in T cell activation? A: They help stabilize the interaction between T cells and antigen-presenting cells. 4. What is the role of costimulation in T cell activation? A: It enhances T cell responses by providing a second signal for activation, in addition to antigen recognition. 5. What are cytokines' role in T cell activation? A: They promote T cell proliferation, differentiation, and function. 6. What is clonal selection and expansion? A: The process by which specific T cells proliferate after recognizing an antigen. 7. What is the effector function of CD4+ T lymphocytes? A: They activate macrophages and other immune cells by secreting cytokines like IFN-gamma. 8. What is the effector function of CD8+ cytotoxic T lymphocytes (CTLs)? A: CTLs kill infected cells by recognizing MHC class I-associated peptides and releasing cytotoxic molecules. 9. How do naive T cells home to lymph nodes? A: By L-selectin binding to high endothelial venules (HEVs). 10. How do effector T cells home to sites of infection? A: Through the interaction of E-selectin, P-selectin, integrins, and chemokines. 11. What is the role of selectins in T cell migration? A: They mediate the initial binding of T cells to the endothelium at sites of infection. 12. What is the role of LFA-1 in T cell migration? A: LFA-1 binds to ICAM-1, facilitating firm adhesion of T cells to the endothelium. 13. What induces E-selectin and P-selectin expression? A: TNF-alpha, IL-1, and LPS. 14. What is the immune response to Listeria monocytogenes mediated by? A: Cell-mediated immunity, specifically T cells. 15. How does adoptive transfer of immune T cells affect Listeria infection? A: It reduces bacterial burden in recipient mice, demonstrating T cell-mediated protection. 16. What cytokine activates macrophages in response to intracellular microbes? A: IFN-gamma, secreted by activated T cells. 17. What is the role of CD40-CD40L interaction in macrophage activation? A: CD40L on T cells engages CD40 on macrophages, enhancing their microbicidal activity. 18. What cytokines are produced by activated macrophages? A: TNF, IL-1, and IL-12, which promote inflammation and T cell activation. 19. How do TH1 and TH2 cells differ in response to infections? A: TH1 cells activate macrophages to kill intracellular microbes, while TH2 cells inhibit macrophage activation. 20. How do CD8+ CTLs kill infected cells? A: By releasing perforin and granzymes, which induce apoptosis in infected cells. 21. What are perforins and granzymes? A: Perforins form pores in target cells, and granzymes enter through these pores to trigger apoptosis. 22. How do CD4+ and CD8+ T cells cooperate in intracellular infections? A: CD4+ T cells activate macrophages to kill vesicular microbes, and CD8+ T cells kill cells with cytoplasmic microbes. 23. How do microbes evade cell-mediated immunity? A: By inhibiting phagosome-lysosome fusion, antigen presentation, or proteasomal activity. 24. How does Mycobacterium tuberculosis evade immune responses? A: By inhibiting phagosome-lysosome fusion through its cord factor. 25. How does herpes simplex virus (HSV) evade immune detection? A: By interfering with the TAP transporter, which prevents antigen presentation. 26. How do cytomegalovirus (CMV) and Epstein-Barr virus (EBV) evade the immune system? A: By inhibiting proteasomal activity and removing MHC I from the endoplasmic reticulum (ER). 27. What role does IL-10 play in microbial evasion of immunity? A: It inhibits macrophage activation, as seen in EBV infection. 28. How do soluble cytokine receptors help microbes evade immunity? A: By inhibiting effector cell activation, as seen with Poxvirus producing soluble IL-1R and IFN-gammaR. 29. What is the importance of MHC class I in cell-mediated immunity? A: MHC class I presents cytoplasmic antigens to CD8+ CTLs for recognition and killing of infected cells. 30. What is the role of MHC class II in cell-mediated immunity? A: MHC class II presents antigens from vesicular microbes to CD4+ T cells, leading to macrophage activation. 31. What is the role of integrins in T cell-mediated killing? A: Integrins stabilize the binding between CTLs and target cells during cytotoxic action. 32. What are cytokines, and how do they affect immune responses? A: Cytokines are signaling molecules that regulate immune cell function, such as activating T cells and macrophages. 33. How do TH1 cells contribute to immunity against intracellular pathogens? A: They secrete IFN-gamma, activating macrophages to kill ingested microbes. 34. What is the primary function of CD8+ cytotoxic T lymphocytes (CTLs)? A: To directly kill virus-infected or cancerous cells. 35. How does the immune system respond to Listeria monocytogenes infection? A: By activating macrophages to kill the bacteria, a process dependent on T cell responses. 36. How does CD40L expression on T cells affect macrophages? A: It binds CD40 on macrophages, enhancing their ability to kill microbes. 37. What is the significance of IFN-gamma in cell-mediated immunity? A: It activates macrophages to kill intracellular pathogens and is a key cytokine in TH1 responses. 38. How do pathogens like Mycobacterium tuberculosis inhibit macrophage function? A: By preventing the fusion of phagosomes with lysosomes, thus evading destruction. 39. What is the result of granzyme release by CD8+ T cells? A: Induction of apoptosis in infected target cells. 40. How do TH1 and TH2 responses affect the outcome of intracellular infections? A: TH1 promotes microbial killing by macrophages, while TH2 can inhibit this process, affecting infection outcomes.