1. Innate Defense
   1. External innate defense
      1. Skin
      2. Mucous membranes
      3. Secretions
      4. Gastric acid
   2. Internal innate defense
      1. Leukocyte
         1. Phagocytic cells
         2. Natural killer (NK) cells
      2. Defensive proteins
         1. Interferons
         2. Complement proteins
      3. Inflammatory response
      4. Lymphatic system
2. Adaptive Defense
   1. Lymphatic system
      1. B cells
         1. Humoral immune response
      2. T cells
         1. Cell-mediated immune response
            1. Helper T cells
            2. Cytotoxic T cells
   2. Antibodies
      1. Monoclonal antibodies
      2. Clonal selection
   3. Antigens
   4. Effector cells
   5. Vaccination
      1. Vaccine
3. Immune Disorders
   1. Allergies
      1. Allergens
      2. Anaphylactic shock
   2. Autoimmune diseases
      1. Systematic lupus erythematousus (SLE)
      2. Rheumatoid arthritis
      3. Insulin-dependent diabetes
      4. Multiple sclerosis (MS)
      5. Crohn's disease
   3. Immunodeficiency diseases
      1. Severe combined immunodeficiency (SCID)
      2. Hodgkin's disease
   4. AIDS
      1. HIV
      2. Promiscuity