The Immune System http://kidshealth.org/kid/htbw/_bfs_ISmoviesource.html

Terms to know Pathogens--- organisms that cause disease Antigen--- a marker molecule on a cell that the immune system uses to recognize a pathogen Antibody--- a chemical that helps destroy a specific kind of pathogen by locking onto a specific marker molecule

Three lines of defense

1. Barriers Skin—forms a physical and chemical barrier Breathing passages---mucus and cilia trap and remove pathogens (sneeze or cough) Mouth and Stomach---most pathogens you swallow are destroyed by chemicals in your salivia or stomach acids

2. Inflammatory response Fluid and certain types of white blood cells leak from blood vessels into nearby tissues. The white blood cells (phagocytes) then fight the pathogen. During the inflammatory response, the affected area becomes red, swollen, and warm. Fever may also occur.

3. Immune response The cells of immune system can distinguish between different kinds of pathogens. The immune system cells react to each kind of pathogens with a defense targeted specifically at that pathogen. White blood cells that target specific pathogens are called lymphocytes.

Two major kinds of lymphocytes T-cells identify pathogens by recognizing their antigens B-cells produce chemicals called antibodies

HIV Human Immunodeficiency Virus Spread through bodily fluids only HIV works like a trojan horse----HIV sneaks inside the T cell and destroys it. HIV goes undetected from the immune system.