The body’s defenses

1. The body’s defenses

2. Lines of defense Lymphatic system Inflammation Features of immune system Memory B-cells Primary and secondary immune responses Antibody Antigen Agglutination macrophage lymphocyte Phagocytosis Complement system Humoral immunity Cell-mediated immunity B cell Helper T cell Cytotoxic T cell Reading: Ch. 43; Keywords

3. Overview

4. Non-specific • First line • Skin • Mucous membranes • Secretions of skin and mucous membranes • Second line • Phagocytic white blood cells • Anti-microbial proteins • Inflammatory response

5. Second line of defense - macrophage

6. Inflamation

9. Focus on immune system(3rd line of defense) • Protects body against specific invaders

10. Key features • Specificity • Diversity • Memory • Self/Nonself Recognition

11. First the major players:Lymphocytes

12. The lymphatic system

13. Two types of immune responses • Humoral • Cell-mediated

14. Key features • Specificity • Diversity • Memory • Self/Nonself Recognition Humoral immunity

15. Humoral immunity: B cells and clonal selection

16. There are a variety of B cells

17. One B cell becomes activated and proliferates

18. Some B cells become plasma cells that secrete antibodies

19. Some B cells become plasma cells that secrete antibodies

20. Some B cells become memory cells

21. Some B cells become memory cells

22. Memory cells function in secondary immune response • Primary immune response - first exposure • Secondary immune response - second exposure

23. Primary and secondary immune responses

24. Summary • Lag in primary response due to proliferation from a single clone • Secondary (2°) response is from multiple memory cells • 2° response has less of a lag and is stronger

25. What do antibodies do?

26. Inactivate antigens

27. Neutralization

28. Agglutination of antigen bearing particles

29. Precipitation of soluble antigens

30. Inactivate antigens • Neutralization • Agglutination • Precipitation

31. These mechanisms enhance phagocytosis

32. Antibodies inactivate antigens • Neutralization of invaders • Agglutination • Precipitation of soluble antigens • The above enhance phagocytosis • One final mechanism: Complement system

33. Complement system: Step 1 attachment to pathogen

34. Step 2: Recruitment of complement proteins

35. Step 3: Activation

36. Step 4: pore formation

37. Summary • Complement proteins interact with antibodies to kill invading cells • Binding of antibody is followed by attachment of complement proteins • Protein complex becomes activated • Pore is formed in pathogen’s membrane • Goodbye pathogen

38. Two types of immune responses • Humoral • Cell-mediated

39. Cell-mediated • Complicated, involves cellular components • Will briefly touch on role of helper T cells

40. Recall that T cells are the other type of lymphocyte

41. Cell-mediated response happens at the same time

42. Macrophage engulfs invader

43. Antigens from invader are presented on macrophage cell surface

44. Helper T cells are recruited

45. Helper T cells proliferate and activate cytotoxic T cells and B cells

46. T cells infected with HIV