The Immune System

The Body’s Defense Pathogens are everywhere. We stay healthy because our body has defenses to keep pathogens out. The immune system fights infection through the production of cells that inactivate unwanted cells A lymphocyte engulfing an invader

Nonspecific Defenses fight or defend against any pathogen First line of defense: Skin Mucus Sweat Tears Second line of defense: inflammatory response fever interferons (fight viruses)

Specific Defenses guard against certain invaders When a pathogen gets past the body’s nonspecific defenses, the immune system attacks. The antigen (invader) triggers the immune response. Future attacks will be met by memory cells

Organs of the Immune System

Humoral Immunity-B cells B lymphocytes (B cells) provide immunity against antigens and pathogens in body fluids B cells recognize invader and produce large numbers of plasma cells and memory B cells Plasma cells release antibodies Antibodies are proteins that recognize & bind to antigens As antibodies overcome infection, plasma cells die off and stop producing antibodies Memory B cells remain in blood stream so they can make plasma cells immediately if ever exposed to the same pathogen again

Cell Mediated Immunity-T Cells Killer T cells track down and destroy bacteria, fungi, protists, or other foreign tissue. Primary defense against the body’s own cells when they have become cancerous or infected by pathogens Helper T cells produce memory T cells. Memory T cells will attack if the same pathogen ever returns. Suppressor T cells shut down the killer T cells when the infection is under control.

HIV attacks T cells HIV (Human Immunodeficiency Virus) attacks the body’s T cells. The immune system is disabled. Victim is not able to fight infection HIV eventually causes AIDS

Vaccines Edward Jenner invented first vaccine in 1769 Injected boy with cowpox virus (weak similar virus to smallpox) Later injected with deadly smallpox virus. Boy had immunity to the virus Vaccines are weakened or “killed” virus or bacteria pathogen. The body responds by creating an immunity to the pathogen (antibodies)