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Adaptive Immunity - Humoral and Cellular Mechanisms

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Terms in this set (23)

  • What are the two overlapping arms of adaptive immunity?
    Humoral immunity (antibody-mediated) and cellular immunity (cell-mediated).
  • What is the main function of humoral immunity?
    Antibodies produced by B lymphocytes circulate in body fluids, temporarily inactivate targets, and mark them for destruction by phagocytes or complement.
  • What distinguishes cellular immunity from humoral immunity?
    Cellular immunity involves T lymphocytes acting directly by killing infected cells or indirectly by releasing chemicals to enhance inflammation or activate other immune cells.
  • What are non-self antigens?
    Substances that provoke an adaptive immune response, usually large, complex molecules not normally found in the body.
  • What are antigenic determinants?
    Specific parts of an antigen that antibodies and lymphocyte receptors bind to; most antigens have multiple determinants.
  • What are self-antigens and why are MHC proteins important?
    Self-antigens are protein molecules on cell surfaces not antigenic to self but antigenic to others; MHC proteins present antigens to T cells for recognition.
  • What are the three main cell types in the adaptive immune system?
    B lymphocytes, T lymphocytes, and antigen-presenting cells (APCs).
  • Where do B and T lymphocytes originate and mature?
    Both originate in red bone marrow; B cells mature in bone marrow, T cells mature in the thymus.
  • What is immunocompetence and self-tolerance in lymphocyte maturation?
    Immunocompetence is the ability to recognize a specific antigen; self-tolerance is unresponsiveness to self-antigens.
  • What happens during positive and negative selection of T cells in the thymus?
    Positive selection ensures T cells recognize self-MHC; negative selection eliminates T cells that bind self-antigens to prevent autoimmunity.
  • What is clonal selection in lymphocyte activation?
    The process where a naive lymphocyte's first encounter with its specific antigen leads to its activation, proliferation, and differentiation.
  • What roles do antigen-presenting cells (APCs) play?
    APCs engulf antigens and present fragments to T cells; major types include dendritic cells, macrophages, and B cells.
  • How are B cells activated and what do they differentiate into?
    B cells are activated when antigens bind and cross-link their receptors; they proliferate and differentiate mainly into plasma cells that secrete antibodies.
  • What is the difference between primary and secondary humoral immune responses?
    Primary response occurs on first antigen exposure with a lag phase; secondary response is faster, stronger, and longer-lasting due to memory cells.
  • What is active humoral immunity?
    Immunity from B cells producing antibodies after encountering antigens naturally or via vaccination.
  • What is passive humoral immunity?
    Immunity gained by receiving ready-made antibodies, without B cell activation or memory formation.
  • Describe the basic structure of an antibody.
    Y-shaped protein with two identical heavy chains and two identical light chains, variable regions form antigen-binding sites, constant regions determine antibody class.
  • Name the five major classes of immunoglobulins (antibodies).
    IgM, IgA, IgD, IgG, and IgE.
  • What are the four main mechanisms of antibody action?
    Neutralization, agglutination, precipitation, and complement fixation.
  • How does neutralization work as an antibody defense mechanism?
    Antibodies block specific sites on pathogens or toxins, preventing them from binding to host cells.
  • What is agglutination in antibody function?
    Antibodies bind multiple antigens on cells, causing clumping that facilitates removal.
  • Explain precipitation as an antibody mechanism.
    Antibodies cross-link soluble antigens, forming complexes that precipitate and are phagocytized.
  • What is complement fixation by antibodies?
    Antibodies bound close together on a cell surface trigger complement activation, leading to cell lysis and enhanced inflammation.