Do Now 3/24/15 1.When was the last time you got sick? What did you have? What were your symptoms? 2.Why do people get sick? 3.What happens to your body when you get sick? 4.Pretend you are a bacteria trying to invade the body. List at least 3 ways the body protects itself against you.

By the end of class today, we will be able to… Define immunity and pathogens to describe how the body fights diseases Describe the relationship between antigens and antibodies and how the body protects itself from foreign particles.

What is immunity? Immune system – defends and protects the body against germs (bacteria, viruses) Pathogens – germs (bacteria, viruses, etc.) that can infect the body Immune system includes: Skin Phagocytes (White Blood Cells) Lymphocytes (B and T cells) Antibodies

Two main groups of pathogens - Bacteria Living cells Contain cell membrane, cell wall, ribosomes, DNA Can reproduce and grow by themselves Can be killed by antibiotic medications Ex: Strep throat, gonorrhea, chlamydia, syphilis

Two main groups of pathogens - Viruses Non-living things Contain DNA surrounded by protein coat Need to infect a human host cell to grow and reproduce Cannot be killed by antibiotics Some antivirals exist Ex: HIV, Herpes, Rabies, Flu

Protection against pathogens Nonspecific defenses – parts of the immune system that defend against ALL bacteria and viruses 1.Physical barriers – skin and mucous membranes prevent particles from entering the body through the surface, “first line of defense” 2.Chemical barriers – enzymes in body fluids help destroy foreign particles (stomach acid, tears, salt from sweat) 3.Fever – increases temperature of the body so foreign enzymes are prevented from working 4.Inflammation – attracts WBC to the site to fight off infections 5.Phagocytosis – cells consume or “eat” another organism to be digested and destroyed

Guess Who? Pair up with a partner Both partners choose one of the nonspecific defenses we discussed Partners alternate asking yes or no questions to try to figure out the identity 3 minutes with notes 3 minutes without notes

Protection against pathogens Specific defenses – parts of the immune system that defend against a certain bacteria and virus Antigen – a (harmful) protein from a pathogen When have we heard antigen before? Antibodies – attach to antigens before they enter a human cell, bring antigens to cells that “eat” them Specific to ONE pathogen