The Immune System Pathogen : Viruses, bacteria, and other microorganisms that cause disease are called pathogens. Infection: Invasion of the tissues of body by pathogens. Defenses Against Infection 1.First line defenses: - Skin- Urine - Sweat- Membranes lining the body passages - Tears - Mucus - Saliva- Stomach acid

The Immune System 2. Second line defenses: Inflammatory response is a reaction of the body that causes swelling, redness, warmth and pain in the area of an infection. Cells that are damaged from the infection release certain chemicals. These chemicals increase the flow of blood to the infected area. The increased blood flow causes puffiness and warmth and attracts

The Immune System 3. Third line defenses: When the inflammatory response defense is insufficient, the pathogen is targeted for destruction by the body’s immune system. The immune system recognizes, attacks, destroys and remembers each kind of pathogen or foreign substance that enters the body. It does this by producing antibodies and specialized cells that bind to and inactivate pathogens. For each kind of pathogen, the immune system produces antibodies or cells that are specific to that pathogen.