Innate & Adaptive Immunity

• Innate Immunity


  Natural immune response which prevents or limits infection
• Adaptive Immunity


  Acquired response which eradicates infection
• Differences between Innate and Adaptive Immunity

  • Resistance: Unaltered on repeated infection (Innate) vs Improved by repeated infection (Adaptive)
  • Specificity: Generally effective against all organisms (Innate) vs Specific for stimulating organisms (Adaptive)
  • Effector Cells: Phagocytes, Macrophages & Neutrophils, NK Cells, Mast Cells, Eosinophils (Innate) vs Lymphocytes, T-Cells & B-Cells (Adaptive)
  • Effector Molecules: Lysosome, Complement Interferons, Alpha, Beta & Gamma Defensins, Lactoferrin (Innate) vs Antibodies & Cytokines (Adaptive)
• Surface Epithelia


  • Epithelial cells line and protect surfaces of the body in contact with the environment
• Mechanisms of Surface Epithelial Protection

  • Mechanical: Cells are joined by tight junctions, Flow of air or fluid across the epithelium, Mucus production and movement by cilia
  • Chemical: Fatty acids and salty sweat in the skin, Lysosome in saliva, sweat and tears, Low pH and pepsin in the stomach, Defensins in the airway and GI tract, Acidity of urine, vaginal lactic acid
  • Microbiological: Symbiotic bacteria compete for nutrients
• Phagocytes


  • Phagocytes engulf, digest and destroy bacteria
• Macrophages


  • Large mononuclear cells found in tissue, Circulate in blood as monocytes
• Neutrophils


  • Multi-lobes nucleus, PMN cells, Many granules in cytoplasm, Circulate in blood (most abundant in white blood cells)
• Eosinophils


  • Bi-lobed nucleus and prominent granules released on contact with parasites and ticks, Found mainly in tissue and low level in circulation, Toxic MBP, ECP EDN
• Mast Cells


  • Found in tissue alongside blood vessels and under epithelial layers, Protect mucosal surfaces, Activated mast cells release histamine in allergic reactions
• Natural Killer (NK) Cells

  • A large granular cytotoxic lymphocyte, Releases lytic granules to kill virus infected cells and some tumour cells, Found in blood, Activated by IFNα, β
• B Cells


  • Formed in bone marrow and carry immunoglobulins on cell surface, Carries receptor that bind one specific antigen, Activated during adaptive immune response to mature into active plasma cells that produce large quantities of specific antibody, The antibodies are secreted into body fluid, blood, and lymph fluid, B cells provide antibody mediated immunity
• T Cells


  • Produced in bone marrow but mature in thymus gland, Antigen receptor on T Cells are known as T Cell Receptors (TCR), During adaptive immune response T Cells divide and proliferate and become activated, Active T Cells must come in close physical contact with their target cells to destroy it, T Cells provide cell mediated immunity
• Antigens


  Antibody generators, Foreign proteins or peptides