INNATE IMMUNE DEFENSES

INNATE IMMUNE DEFENSES

1. PHYSICAL AND CHEMICAL BARRIERS

   • Skin, respiratory tract, digestive tract and urinary tract
     • Secretion of oil glands, mucus, saliva, tears, milk and acidic pH in stomach

2. INFLAMMATORY RESPONSE

   • Injured tissue cells and mast cells release histamine and other chemical mediators
     • Redness, heat, swelling and pain
     • Macrophages and dendritic cells phagocytize phatogens and release cytokines
       • Neutrophils and monocytes (macrophages) squeeze through capillary wall and phagocytize phatogens
         • Blood clot form (prevent blood loss)

3. PHAGOCYTES AND NATURAL KILLER CELLS

   • Neutrophils
     • Leave the bloodstream and phagocytize bacteria
     • Release antimicrobial peptides and enzyme that digest bacteria
     • Generate free radicals (superoxide and h2o2) to kill engulfed bacteria
   • Eosinophils
     • Phagocytic
       • Attack animal parasites (tapeworms) - too large to be phagocytized
   • Macrophages and dendritic cells
     • Engulf phatogens
       • Stimulate T cells in lymph nodes
   • Natural killer (NK) cells
     • Large, granular lymphocytes
     • Kill virus-infected cells and cancer cells (cell-to-cell contact)
       • Seek for cells that lack MHC-I molecules
         • Do not increase in numbers after stimulation

4. PROTECTIVE PROTEINS

   • Complement
     • Plasma protein produce by liver and activated by phatogens
     • Enhanced inflammation
       • Increase phagocytosis- bind to phatogens
         • Membrane attack complexes- produce hole
           • Fluid and salts enter (burst)
   • Interferons
     • Cytokines that affect the behavior of other cells
       • Made by virus-infected cells
         • Treat certain cancers and viral infections (hepatitis C)
     • Bind to virus infected cells
       • Slow metabolism and interfere with viral replication