In-Depth Notes on Immunity and Immune Response

  • Immunity Acquisition

    • Two main categories:
    • Natural Immunity
      • Active Natural Immunity: Your body produces antibodies after natural exposure to pathogens.
      • Passive Natural Immunity: Antibodies transferred from mother to child. (e.g., through placenta or breast milk)
    • Artificial Immunity
      • Active Artificial Immunity: Immunization via vaccines, where the body learns to produce antibodies against weakened or inactive pathogens.
      • Passive Artificial Immunity: Transfer of antibodies from another individual (e.g., convalescent plasma from a COVID-19 survivor).

  • Innate vs. Adaptive Immunity

    • Innate Immunity: Nonspecific, immediate response, includes physical barriers and certain immune cells (e.g., phagocytes).
    • Adaptive Immunity:
    • Slower Response: Requires time to recognize and process antigens.
    • Specific Response: Involves B and T lymphocytes targeting specific pathogens.

  • B Cells and T Cells

    • B Cells:
    • Originates in the bone marrow and matures in it.
    • Activated by antigens, differentiates into:
      • Memory B Cells: Remembers past infections.
      • Plasma Cells (Effector B Cells): Secretes antibodies targeting pathogens.
    • T Cells:
    • Originates from stem cells in the bone marrow but matures in the thymus.
    • Types:
      • CD4 T Cells (Helper T Cells): Activate other immune cells.
      • CD8 T Cells (Cytotoxic T Cells): Directly kill infected cells.

  • Antibody Structure and Classes

    • General Structure: Y-shaped, with a constant region and a variable region (where antigen binding occurs).
    • Classes of Antibodies (Immunoglobulins):
    • IgG:
      • Most abundant in circulation, crosses placenta, provides passive natural immunity to newborn.
    • IgM:
      • First antibody produced in response to infection, indicates active primary immune response.
    • IgA:
      • Found in secretions (saliva, tears), plays role in mucosal immunity.
    • IgE:
      • Involved in allergic reactions and responses to parasites.
    • IgD:
      • Less understood, found on the surface of B cells, involved in their activation.

  • Immune Response Phases

    • Primary Immune Response: Initial response to a pathogen, involves gradual increase in specific antibodies.
    • Secondary Immune Response: Faster and stronger due to memory cells (e.g., memory B and T cells) that recognize previously encountered pathogens.

  • Optimization:

    • Process by which antibodies mark pathogens for destruction by immune cells (e.g., through opsonization).

  • Importance of Cell-Mediated Immunity: Involves direct attack by T cells and other immune cells against infected or cancerous cells, crucial in eliminating intracellular pathogens.