NOTES: CH 35 The Immune System and Disease

1. NOTES: CH 35 The Immune System and Disease

2. CH 35: Key Terms / Concepts • Key Terms • Infectious disease • Pathogen • Antigen • Antibody • Immunity • Vaccination • Concepts • What causes infectious diseases and how do they spread? • How do our bodies respond to these pathogens? • How do we prevent infectious diseases to spread?

3. 35.1 – Infectious Disease • PATHOGEN: a disease-causing agent; disrupt normal body functions -pathogens include: virusesfungi bacteriaprotozoans

4. Examples of viruses: Small pox Common Cold Herpes Polio

5. How are Diseases Spread? • Coughing, sneezing, physical contact • Exchange of body fluids • Contaminated food and water • Animal contact (zoonosis) -VECTOR = an organism that transports the pathogen, but does not get sick.

6. 35.2 – Defenses Against Infection HOW DO WE FIGHT OFF DISEASE? The body has nonspecific and specific defenses against infection.

7. Nonspecific Defenses: • provide protection against a wide range of pathogens • involve physical & chemical barriers, fever, inflammation, interferons

8. FIRST LINE OF DEFENSE = Mechanical Barriers ● mechanical barriers / physical barriers include: -skin (and associated hairs) -mucus membranes / mucus -fluid (sweat, tears) ● as long as they remain intact, they can keep out many pathogens

10. FIRST LINE OF DEFENSE also includes: ● CHEMICAL BARRIERS •mucus – traps pathogens •stomach secretions: may destroy pathogens that get swallowed

11. Chemical Barriers – cont. • tears: contain the enzyme LYSOZYME (which has antibacterial action) • salt in sweat: kills bacteria on the skin

12. **all other “nonspecific defenses” are considered the SECOND LINE OF DEFENSE

13. 1) Inflammation • produces: localized redness, swelling, heat and pain • chemicals released by damaged tissues attract WBCs to the site  the mass of WBCs, bacterial cells, and damaged tissue forms a thick fluid called PUS

14. 2) INTERFERONS: chemicals released by virus-infected cells; “interfere” with viral growth – slow down viral reproduction!

16. 3) Fever • higher body temperature speeds up some white blood cells • slows the growth of some pathogens

17. SPECIFIC DEFENSES!(“Immunity”)

18. Specific Defenses: • able to distinguish “self” from “non-self” or “other” • any foreign substance or cell that enters the body is inactivated or killed

19. Specific Defenses: • precise / target certain pathogens • also known as IMMUNITY • involve specialized lymphocytes (T cells and B cells)

20. ANTIGENS… • ANTIGENS: specific foreign molecules that trigger an immune response; usually located on a foreign cell’s surface

21. LYMPHOCYTES (T and B Cells) • originate in the bone marrow • some reach the THYMUS, where they mature into T CELLS • others, the B CELLS, mature in the BONE MARROW • once mature, both T cells and B cells “hang out” in the lymph nodes & spleen where they will encounter antigens

22. LYMPHOCYTE FUNCTIONS **there are two main types of lymphocyte action: 1) Humoral Immunity 2) Cell-Mediated Immunity

23. 1) HUMORAL IMMUNITY ● B cells interact with antigen-bearing cells indirectly, producing the HUMORAL IMMUNE RESPONSE ● some B cells differentiate into PLASMA CELLS which produce ANTIBODIES

24. How do antibodies bind to antigen? • ANTIBODIEShave a specific shape that allows it to bind to specific antigen. • Once antibodies have “tagged” antigen, the pathogen is “flagged” for disposal by other cells

25. HUMORAL IMMUNITY ● other B cells divide and remain around after the infection – MEMORY B CELLS ● these cells react quickly if the same pathogen returns

26. T CELLS and the CELL-MEDIATED IMMUNE RESPONSE * T cells are activated when an antigen-presenting cell displays a foreign antigen antigen T cell! Antigen Presenting Cell (APC)

28. 2) CELL-MEDIATED RESPONSE ● HELPER T CELLS are activated when they encounter foreign antigen-bearing cells ● they then divide to produce more helper T cells, which in turn go on to: -activate B cells(antibodies!) -activate cytotoxic T cells -produce memory T cells

29. T CELLS (continued) ● cytotoxic T cells:kill infected (“sick”) cells ● memory T cells:remain in the blood and respond quickly if the pathogen returns.

31. 35.3 – Fighting Infectious Disease ● PRIMARY IMMUNE RESPONSE ● SECONDARY IMMUNE RESPONSE

32. PRIMARY IMMUNE RESPONSE • PRIMARY IMMUNE RESPONSE: the first exposure to an antigen  during this response, antibodies are produced for several weeks  antibodies first show up within 5-10 days  some B cells remain as MEMORY CELLS

33. SECONDARY IMMUNE RESPONSE • SECONDARY IMMUNE RESPONSE: the second exposure to an antigen • rapid responsedue to memory cells produced during the first exposure  antibodies produced within a day or two

35. CLASSIFICATION OF IMMUNITY 1) ACTIVE IMMUNITY ● when the person produces an immune response (including memory cells) to the antigen ● a result of direct exposure to the antigen ● long-lasting (memory cells)

36. ACTIVE IMMUNITY… • NATURALLY ACQUIRED ACTIVE IMMUNITY: person is directly exposed to the pathogen, develops a disease, gets better, & acquires immunity • ARTIFICIALLY ACQUIRED ACTIVE IMMUNITY: person receives a vaccine

37. VACCINES… **A VACCINE consists of bacteria or viruses that have been weakened or killed so they cannot cause a serious infection -includes antigens that stimulate a primary immune response but does not produce the severe symptoms of disease

39. 2) PASSIVE IMMUNITY ● person receives antibodies produced by another individual ● this is short-term only (as long as the antibodies remain in the blood) – no memory cells! ● the person remains vulnerable to the antigen if exposed at a later date

40. PASSIVE IMMUNITY • NATURALLY ACQUIRED PASSIVE IMMUNITY: fetus acquires immunity from mother through placenta and/or breast milk ARTIFICIALLY ACQUIRED PASSIVE IMMUNITY: person receives an injection of antibodies collected from a person who has already developed immunity against a particular disease (i.e. rabies)

42. Public Health - Prevention of Diseases Spreading 1) Regulating food and water supplies ● Cholera, Typhoid, Guinea worm

43. Public Health - Prevention of Diseases Spreading 2) Promoting vaccinations ● Herd immunity

45. Public Health - Prevention of Diseases Spreading 3) Promoting behaviors that avoid spread of infection

46. New and Re-Emerging Diseases ● Many diseases were eliminated or were under control by the 1980s • e.g. polio and smallpox ● Over the past decade, we have had a resurgence of old diseases and introduction of new diseases • Ebola, SARS, hantavirus ● Why has this happened??

47. Reasons for New and Re-Emerging Diseases 1) Changing interactions with Animals -Human and animal habitats combine -Trade of exotic animals

48. Reasons for New and Re-Emerging Diseases 2) Misuse of Antibiotics and medications -Not following instructions on medication -Overuse of antibiotic causing resistance

49. 35.4 – Immune System Disorders ● Allergies ● Autoimmune Diseases ● Attack on the Immune System (HIV / AIDS)

50. ALLERGIC REACTIONS ● triggered by antigens known as ALLERGENS ● the immune system attacks a nonharmful substance, such as pollen, pet dander, peanuts