The Body's DefensesImage result for medieval castle attack









  1. Surface defenses
  2. Nonspecific (innate) immunity
  3. Adaptive immunity

Cells of the immune system

  1. White blood cells (leukocytes)
    1. Lymphocytes
      • B-cells: antibody production
      • T-cells: cell-mediated immunity
      • Natural Killer cells: cancer/virus cell surveillance
    2. Mononuclear cells
      • Monocytes: precursors of macrophages
      • Macrophages: phagocytosis, antigen presentation, cytokine release
        • MHC-II antigen, IgG receptor, C3b receptor
        • Secrete cytokines -- inflammation, fever
    3. Granulocytes
      • Neutrophils (PMN): phagocytosis, inflammation; pus
      • Eosinophils: defense vs. parasites
      • Basophils: histamine release
  2. Tissue (resident) cells
    1. Mast cells
    2. Resident (tissues) macrophages
      • Kupffer cells (liver)
      • Microglia
      • Alveolar macrophages
      • Intraglomerular mesangial cells
    3. Dendritic cells (skin, liver, lymph nodes, spleen, blood, thymus)
      • phagocytosis
      • antigen presentation (MHC-II)
      • cytokine release
  3. Immune system organs

Innate Immunity

A. Complement

B. Phagocytosis 

  1. Opsonization - coating of pathogen surface to mark it for phagocytosis
  2. Opsonin-independent mechanisms

Phagocytes respond to chemoattractant mediators, e.g. C5a

C. Inflammation

  1. Signs:
  2. Causes
    1. Tissue damage (wound/trauma): endothelial cells --> IL-1, 6
    2. Pathogens (via macrophages, complement)
  3. Inflammatory Response
  4. Results of inflammation

D. Fever

  1. Macrophage, damages tissues release cytokines s.a. IL-1 and TNF-a
  2. IL-1 & TNF-a  stimulate hypothalamus via prostaglandin synthesis to increase temperature
  3. Increased temperature stimulates immune system and inhibits pathogens

E. Cytokines

  1. Cytokines are chemical mediators released by immune system cells
  2. Cytokines have several important functions
  3. Many cytokines are released by macrophages
  4. 3 major classes:

F. Interferon

  1. IFN-a and IFN-b
  2. Produced by virally infected cells and lymphocytes
  3. Stimulate neighboring cells to produce anti-viral proteins

G. Chemotaxis

  1. Attraction of phagocytes to site of infection

H. Acute Phase Response

  1. Triggered by IL1, IL6, TNF-a, inflammation, tissue injury, PGE2, INF
  2. Promotes host defense