The Body’s Defenses: The Immune System

1. The Body’s Defenses: The Immune System Chapter 43 Part I

2. Pathogens • Disease causing agent: • Bacteria • Protists • Fungus • Viruses • Other microorganisms • Own cells gone awry

3. Your body fights back • It’s evolutionarily disadvantageous to die

4. Two ways to fight • Innate immunity • Defense before any exposure to pathogen • Acquired immunity • Defense builds in response to present pathogen

5. Innate Immunity • What you are born with • Nonspecific – fight a broad range of pathogens

7. Nonspecific Defenses • 1st line of defense: • Skin and mucous membranes • Prevent entry of pathogens • Intact epidermis, hairs filter • Secretions: • Acids – inhibit growth of microorganisms, destroy bacteria • Mucous – wash away and trap • Chemicals – lysozymes to destroy cell walls

8. Nonspecific Defenses • 2nd line of defense: • Phagocytes • Engulf and digest foreign cells and particles • Macrophages • Monocytes • Eosinophils • Neutrophils • Basophils • Mast cells • Natural killer cells

9. Nonspecific Defenses • 2nd line of defense: • Interferons • Secreted by virally infected cells, stimulates neighboring cells to secrete anti-viral chemicals

10. Nonspecific Defenses • 2nd line of defense: • Complement system • Attract phagocytes; found in plasma • Triggered by antibodies bound to antigen • Form pore in bacteria

11. Nonspecific Defenses • 2nd line of defense: • Inflammation • Histamine release dilates vessels • Increased blood supply due to dilation causes redness and warmth • Swelling (edema) of affected area caused by fluid loss from vessels • Increased blood flow brings in more phagocytes to infected area

12. Nonspecific Defenses • 2nd line of defense: • Fever • Widespread inflammatory response • Pyrogens from WBC’s “reset” thermostat in hypothalamus • Fever interferes with viral activity

13. Connecting it all!