48.Cellular immunity. Cell-cell interactions in the immune response. T- and B-cell receptors and their activation.
Covers cellular immunity, its effector arms and the roles of CD4 and CD8 T cells, then the three T helper subsets (Th0, Th1, Th2) and how they regulate one another through cytokines. It goes on to hapten–carrier cell cooperation in T-dependent antibody responses, T-independent antibody responses with their type 1 and type 2 forms, NK and LAK cell activation, and the two-signal model of T and B cell activation. A comparison of T-dependent and T-independent B cell responses and a note on the MHC class I and II peptide lengths are included.
Topic 48 of 63 in the MU Pleven syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 8 sections, about 990 words (7 min of reading), with 55 flashcards.
In this note
Cellular immunity. Cell-cell interactions in the immune response. T- and B-cell receptors and their activation.
Cellular Immunity
T Cells and Their Functions
Cell–Cell Interactions in Antibody Responses to Exogenous T-Dependent Antigens
Antibody Responses to T-Independent Antigens
Activation of Natural Killer (NK) Cells
T Cell Activation
B Cell Activation
Cellular Immunity
Cellular immunity is an immune response that does not involve antibodies. Instead, it relies on the activation of phagocytes, antigen-specific cytotoxic T lymphocytes, and the release of cytokines in response to antigen exposure.
CD4⁺ T helper cells play a central role by providing protection against different pathogens. Cytotoxic T cells (CD8⁺) induce cell death by apoptosis without the direct use of cytokines; therefore, cytokines are not always present in cell-mediated immune responses.
Cellular immunity protects the body through several coordinated mechanisms. It activates antigen-specific cytotoxic T lymphocytes that induce apoptosis in body cells displaying foreign antigen epitopes, such as virus-infected cells, cells containing intracellular bacteria, and cancer cells expressing tumour antigens. It also activates macrophages and natural killer (NK) cells, enhancing their ability to destroy pathogens. In addition, cellular immunity stimulates cells to secrete a wide range of cytokines that regulate both adaptive and innate immune responses.
This arm of immunity is directed mainly against microbes that survive within phagocytes and microbes that infect non-phagocytic cells. It is particularly effective against virus-infected cells, but also contributes to defense against fungi, protozoa, intracellular bacteria, and cancer cells. Cellular immunity also plays a major role in transplant rejection.
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