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Adaptive Immunity quiz #1

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  • What are the main differences between B cell receptors and T cell receptors in the adaptive immune system?
    B cell receptors can bind directly to free antigens, while T cell receptors only recognize antigens that are presented on the surface of other cells via MHC proteins. Structurally, B cell receptors are similar to antibodies with heavy and light chains, whereas T cell receptors have alpha and beta chains.
  • How does the adaptive immune system achieve specificity and diversity in antigen recognition?
    The adaptive immune system achieves specificity and diversity through genetic recombination of variable, joining, and other gene segments in B and T cell receptors, resulting in a vast array of unique antigen receptors capable of recognizing many different antigens.
  • What is the role of Major Histocompatibility Complex (MHC) proteins in antigen presentation?
    MHC proteins display antigen fragments on the cell surface. MHC class I is found on all body cells and presents intracellular antigens, while MHC class II is found on antigen-presenting cells and presents extracellular antigens to T cells.
  • Describe the process of clonal selection and its significance in the adaptive immune response.
    Clonal selection occurs when a lymphocyte with a receptor specific to an antigen is activated, leading to its proliferation into a clone of effector and memory cells. This ensures a targeted and amplified immune response against the specific pathogen.
  • What are the primary functions of cytotoxic T cells and helper T cells?
    Cytotoxic T cells kill infected cells by inducing cell death, while helper T cells assist in activating other immune cells, such as B cells and cytotoxic T cells, by secreting cytokines.
  • How do vaccines provide immunity against infectious diseases?
    Vaccines introduce antigens from pathogens (often in weakened or inactivated forms) to prime the immune system, leading to the formation of memory cells. This allows for a rapid and strong secondary immune response upon future exposure to the pathogen.
  • Explain the difference between the primary and secondary immune responses.
    The primary immune response occurs upon first exposure to an antigen and is slower with lower antibody production. The secondary response is faster and stronger due to the presence of memory cells generated during the primary response.
  • What mechanisms do antibodies use to neutralize or eliminate pathogens?
    Antibodies neutralize pathogens by binding and blocking their activity, promote opsonization to enhance phagocytosis, cause agglutination (clumping) of pathogens, and activate complement proteins to destroy pathogens.
  • How does the adaptive immune system prevent autoimmunity?
    During lymphocyte maturation, cells with receptors that bind self-molecules are destroyed or deactivated, preventing the immune system from attacking the body's own tissues.
  • Why does HIV infection lead to immunodeficiency, and what is AIDS?
    HIV infects and destroys CD4+ helper T cells, which are essential for activating both B cells and cytotoxic T cells. The loss of these cells weakens the immune system, leading to AIDS (Acquired Immune Deficiency Syndrome), where the body cannot effectively fight infections.