Skip to Main Content


Immune system components: balanced response by these components ensures elimination of threat with minimal damage to surrounding tissues (Table 73-1).

  • Innate immunity:

    • Pattern recognition receptors (PRRs) = present on most cells, recognize pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs). Lead to the production of cytokines and chemokines to contain threat and recruit cellular components of the immune system. Include the toll-like receptors (Table 73-2), Toll-like and Nod-like receptors, RIG-like receptors, and C-type lectin receptors.

    • Opsonins = mark pathogens or cells for clearance by phagocytes.

    • Complement = opsonize or directly lyse pathogens via assembly of the membrane attack complex.

    • Cells = including neutrophils, monocytes/macrophages, dendritic cells, and natural killer cells.

  • Adaptive immunity:

    • T cells.

      • CD4+ helper T cells:

        • Th1: Triggered by bacteria and viruses. Primary cytokines include IL-2, IFN-γ, TNF.

        • Th2: Triggered by parasites and allergic reactions. Primary cytokines include IL-4, IL-5, IL-10.

        • Th17: Very inflammatory. Primary cytokine is IL-17.

      • CD8+ cytotoxic T cells: Kill infected cells.

    • B cells.

      • Plasma B cells: Antibody factories.

      • Memory B cells: Provide long-term protection.

TABLE 73-1

Examples of Key Effector Molecules of the Innate Immune System

TABLE 73-2

Key Pattern Recognition Receptors from the Toll-Like Receptor Family


Excessive inflammation: can cause collateral damage to tissues.

  • Symptoms: fever or hypothermia, tachycardia, tachypnea, abnormally ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.