Immune System First Line Defenses

Second Line Defense: Inflammatory Response

Second Line Defense: Temperature Response

Lymphatic System

Cell Mediated Response

Step 1: Virus enters human body Step 2: Macrophage engulfs virus and displays viral antigens on its cell surface (MHC prevents attack by other immune cells) Step 3: Helper T-cell binds to viral antigen on macrophage Step 4: Macrophage releases IL-1 which triggers Helper T-cells to release IL-2 Step 5: IL-2 triggers division of Helper T-cells and Killer T-cells Step 6: Killer T-cells bind to viral antigens on infected body cells and inject toxin Step 7: Toxin destroys infected body cell and virus

Humoral Response

Step 1: Helper T-cells secrete IL-2 and activate B-cells that recognize the antigen Step 2: Activated B-cells replicate Step 3: B-cells secrete antibodies Step 4: Antibodies bind to antigens on virus; inactivate virus and mark it for destruction Step 5: Macrophage engulfs viruses coated with antibodies Step 6: Antibodies bind to antigens on infected body cells; mark cells for destruction Step 7: Some B-cells become memory B-cells to protect against re-infection by same virus

Skin Phagocytes and Lymphocytes MHCs Lymph nodes/Blood vessels MHCs Antibodies Engulfed by macrophage/Covered with antibodies Phagocytes Displaying antigens Interleukins Killer T-cells Memory B-cells