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Adaptive Immunity and Antigen Recognition in Microbiology

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  • What is an antigen?

    An antigen is any molecule or molecular structure that can be recognized by the immune system and elicit an immune response.
  • Define epitope.

    An epitope is the specific part of an antigen that is recognized and bound by a T or B cell receptor.
  • What is a hapten?

    A hapten is a small molecule that is not immunogenic by itself but can elicit an immune response when attached to a larger carrier molecule.
  • Explain immunogenicity.

    Immunogenicity is the ability of an antigen to provoke an immune response, influenced by factors like size, complexity, and foreignness.
  • What role do T cell receptors (TCRs) play in antigen recognition?

    T cell receptors recognize processed antigen fragments presented by MHC molecules on antigen-presenting cells.
  • How do B cell receptors (BCRs) recognize antigens?

    B cell receptors bind directly to native antigens in their natural form without processing.
  • How is receptor diversity generated in T and B cells?

    Receptor diversity arises through somatic recombination of gene segments encoding the variable regions of TCRs and BCRs.
  • Define self-tolerance in adaptive immunity.

    Self-tolerance is the immune system's ability to avoid attacking the body’s own cells and molecules.
  • How are immature T and B cells screened for self-tolerance?

    Immature T and B cells undergo negative selection in the thymus and bone marrow to eliminate cells that strongly react to self-antigens.
  • What is the cellular branch of adaptive immunity?

    The cellular branch involves T cells that directly kill infected cells or help other immune cells.
  • Name key effector cells of the cellular adaptive immune response.

    Key effector cells include cytotoxic T cells (CD8+) and helper T cells (CD4+).
  • What are the two types of MHC molecules?

    The two types are MHC class I and MHC class II molecules.
  • How does MHC class I present antigens?

    MHC class I presents endogenous antigens from inside the cell to CD8+ cytotoxic T cells.
  • How does MHC class II present antigens?

    MHC class II presents exogenous antigens from outside the cell to CD4+ helper T cells.
  • How do MHC molecules impact transplant rejection?

    Differences in donor and recipient MHC molecules cause immune recognition of transplanted tissue as foreign, leading to rejection.