1. The Immune System

2. Immune system  Recognizes, attacks, destroys, and “remembers” each type of pathogen that enters the body  Immunity is the process of producing cells that inactivate foreign substances in the body  2 categories in the immune system  Specific defenses  Nonspecific defenses

3. Nonspecific defenses  Include physical and chemical barriers (skin, mucus, sweat, tears)  Keep pathogens out of the body  Body secretions (mucus, saliva, and tears) contain lysozyme, an enzyme that breaks down bacteria  Oil and sweat glands provide an acidic environment that inhibits bacterial growth  Mucus in nose and throat trap pathogens  Cilia in nose and throat push pathogens away from lungs  Digestive enzymes break down pathogens

4. Second line of defense  Inflammatory response-body responds to tissue damage caused by injury or infection  Millions of white blood cells fight infection  Blood vessels near would expand and allow WBCs to pass into wounded area  WBCs engulf bacteria; affected area can become swollen and painful

5. To return to the chapter summary click escape or close this document. Macrophage

6. To return to the chapter summary click escape or close this document. Histamine Production

7. Fever  Immune system releases chemicals that raise the body’s core temperature  Higher temperature helps to destroy pathogens (cannot survive high heat)  Fever also increases heart rate which allows WBCs to get to would or infection faster

8. Interferon  Proteins produced by viral-infected cells that help other cells resist viral infection  Interferons inhibit the synthesis of viral proteins in infected cells and block viral reproduction  Gives immune system time to respond

9. Specific defenses  Attack particular disease-causing agents  Make up the immune response  Antigens (viruses, bacteria, other pathogens) trigger this response  Two types of lymphocytes in the immune response  B lymphocytes (B cells)  T lymphocytes (T cells)

10. B cells  Provide immunity against antigens in body fluids  Recognize antigens, grow and divide rapidly to make plasma cells and memory B cells  Plasma cells release antibodies (proteins that recognize and bind to antigens) into the blood to go and attack the pathogen  Memory B cells remain capable of producing the antibodies in case a second infection occurs

11. To return to the chapter summary click escape or close this document. Antibody Immunity

12. T cells  Provide defense against abnormal cells and pathogens living in cells (cancerous cells or viral-infected cells)  Cell-mediated immunity  Also helps against infections by fungi or protists  T cells become killer T cells, helper T cells, suppressor T cells, and memory T cells

13. To return to the chapter summary click escape or close this document. Cellular Immunity

14. Killer T cells  Track down and destroy bacteria, fungi, protozoa, or foreign tissue that contains a pathogen or antigen

15. Helper T cells and memory T cells  Helper T cells produce memory T cells  Memory T cells cause a secondary response in case of another infection by the same pathogen

16. Suppressor T cells  Release substances that shut down the killer T cells

17. Active immunity  Caused by injection of a weakened or mild form of a pathogen to produce immunity (vaccines)  Modern vaccines stimulate the immune system to create millions of plasma cells ready to produce specific types of antibodies  Can also be developed after natural exposure

18. Passive immunity  Antibodies produced by other animals are injected into the body to produce antibodies  Last only a short time before the body destroys them  Can be developed from natural exposure or vaccines  Antibodies can also move across the placenta during pregnancy or be passed to infants in breast milk