PowerLecture: Chapter 10

1. PowerLecture:Chapter 10 Immunity

2. Learning Objectives • Describe typical external barriers that organisms present to invading organisms. • Understand how the lymphatic system contributes to the body’s defenses. • Understand how vertebrates (especially mammals) recognize and discriminate between self and nonself tissues. • Distinguish between antibody-mediated and cell-mediated patterns of immune responses.

3. Learning Objectives (cont’d) • Describe some examples of immune failures and identify as specifically as you can which weapons in the immunity arsenal fail in each case.

4. Impacts/Issues The Face of AIDS

5. The Face of AIDS • Viruses, such as HIV, have wide ranging impacts on human health. • At least 40 million people are infected with HIV; 12 million African children alone have been orphaned by AIDS. • Rates of new HIV infection are declining in some areas, but we still have no effective vaccine to prevent infection.

6. The Face of AIDS • The immune system is responsible for protecting us from HIV and other infectious agents; the more we learn about this system, the more opportunities we have to improve our health.

7. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu. • Should the federal government offer incentives to companies to discount the drugs for developing countries? • a. Yes, drug companies have a responsibility to world health, not just their bottom line. • b. No, if drug companies must provide subsidies, they won't be able to afford to develop new drugs.

8. Section 1 Overview of Body Defenses

9. Overview of Body Defenses • We are born with some general defenses and acquire other, specific ones. • We have many defenses to protect us from pathogens—those viruses, bacteria, fungi, protozoa, and parasitic worms that cause disease. • Antigens on these pathogens identify them as nonself. • Antigens are usually proteins, lipids, or oligosaccharides.

10. Overview of Body Defenses • Immunity is the body’s overall ability to resist and combat anything that is nonself. • Innate immunity encompasses preset responses that activate rapidly and in a generalized way to detected damage or invasion. • Adaptive immunity responds to specific antigens on specific pathogens; this response takes longer to develop, but the body “remembers” what it sees and responds quicker the next time the same pathogen is seen.

11. Table 10.1, p.176

12. Overview of Body Defenses • Three lines of defense protect the body. • Intact skin and mucous membranes are important first-line physical barriers. • Innate immunity forms the second line of defense. • Adaptive immunity forms the third line of defense.

13. Overview of Body Defenses • White blood cells and their chemicals are the defenders in immune responses. • White blood cells are the core of the immune system. • Phagocytes release chemicals called cytokines to further defense responses. • Cytokines regulate different aspects of the immune response; interleukins affect inflammation and fever, interferons defend against viruses, and tumor necrosis factor also affects inflammation and stimulates tumor cell death.

14. Overview of Body Defenses • Complement is a group of about 30 blood proteins that can kill microbes or identify them for phagocytes to destroy. • White blood cells serve a variety of different functions in the immune response: • Neutrophils make up two-thirds of all white blood cells and work at the site of inflammation or damage. • Basophils and mast cells produce histamines in response to antigens. • Macrophages are the predominant phagocytes that patrol the bloodstream.

15. Overview of Body Defenses • Eosinophils target pathogens that are too large for the macrophages. • Dendritic cells signal when antigens are present in skin and body linings. • B and T lymphocytes (B and T cells) function in adaptive immunity. • Natural killer cells (NK cells) are lymphocytes that function in innate responses.

16. Table 10.2, p.177

17. neutrophil eosinophil Fig. 10.1, p.177

18. basophil mast cell Fig. 10.1, p.177

19. T lymphocyte (T cell) B lymphocyte (B cell) Fig. 10.1, p.177

20. dendritic cell macrophage Natural killer (NK) cell Fig. 10.1, p.177

21. Animation: White Blood Cells CLICKTO PLAY

22. Section 2 The Lymphatic System

23. The Lymphatic System • The lymphatic system has two key roles: to work with the cardiovascular system to cycle fluids back into the circulation; and to circulate lymph from the spleen, lymph nodes, and other lymphoid tissues throughout the body.

24. Tonsils Defense against bacteria and other foreign agents Right Lymphatic Duct Drains right upper portion of the body Thymus Site where certain white blood cells acquire means to chemically recognize specific foreign invaders Thoracic Duct Drains most of the body Spleen Major site of antibody production; disposal site for old red blood cells and foreign debris; site of red blood cell formation in the embryo Some of the Lymph Vessels Return excess interstitial fluid and reclaimable solutes to the blood Some of the Lymph Nodes Filter bacteria and many other agents of disease from lymph Bone Marrow Marrow in some bones is production site for infection-fighting blood cells (as well as red blood cells and platelets) Fig. 10.2, p.178

25. Animation: Lymphoid Organs CLICKTO PLAY

26. The Lymphatic System • The lymph vascular system functions in drainage, delivery, and disposal. • The lymph vascular system consists of lymph capillaries and other vessels linking it to the cardiovascular system. • Water and solutes that drain from the blood vessels collect in the lymphatic vessels and are returned to the blood via these vessels. • The lymphatic vessels pick up absorbed fats and deliver them to the blood. • Lymphatic vessels also transport foreign material to the lymph nodes for disposal.

27. The Lymphatic System • Lymph capillaries and vessels are structured much like blood capillaries and veins.

28. blood capillary bed lymph capillary interstitial fluid flaplike “valve” formed from overlapping cells at the tip of a lymph capillary a Lymph capillaries Fig. 10.3a, p.179

29. The Lymphatic System • Lymphoid organs and tissues are specialized for body defense. • Lymph nodes are located at intervals along the lymph vessels; lymphocytes congregate in these nodes, making them key battlefields in fighting off pathogens.

30. lymph trickles past organized arrays of lymphocytes within the lymph node valve (prevents backflow) b A lymph node, cross section Fig. 10.3b, p.179

31. Animation: Human Lymphatic System CLICKTO PLAY

32. The Lymphatic System • The spleen filters blood and serves as a holding station for large numbers of lymphocytes. • T cells are produced and become specialized in the thymus.

33. Section 3 Surface Barriers

34. Surface Barriers • The normal microorganisms living on your skin help prevent the growth of unwanted pathogens through competition. • Some microorganisms, such as the Lactobacillus species of the vaginal tract in women, lower the pH of their surroundings to prevent growth of other microbes. Figure 10.4

35. Surface Barriers • The mucus coating your lungs contains enzymes such as lysozyme that can attack and destroy many bacteria; cilia can also sweep out pathogens. • Chemicals in tears, saliva, and gastric fluid offer similar protection. • The natural low pH of urine, as well as its flushing action, helps protect the urinary tract.

36. Section 4 Innate Immunity

37. Innate Immunity • Once a pathogen enters the body, macrophages engulf it and release cytokines to attract dendritic cells, neutrophils, and more macrophages. Figure 10.5

38. Innate Immunity • Circulating complement proteins can detect pathogens and become activated. • Activated complement attracts phagocytes, which can destroy the pathogens. • Activated complement can also form membrane attack complexes in the pathogen; these are holes that cause the pathogen to disintegrate.

39. Fig. 10.6, p.180 one membrane attack complex (cutaway view) lipid bilayer of a pathogen pore

40. Animation: Membrane Attack Complexes CLICKTO PLAY

41. Innate Immunity • Activated complement and cytokines stimulate inflammation, characterized by redness, swelling, warmth, and pain. • Tissue irritation causes mast cells to release histamine and cytokines that cause the blood vessels to dilate (tissue redness and warmth) and capillary walls to become leaky (edema). Figure 10.8

42. Innate Immunity • Plasma proteins and phagocytes leave the blood vessels. • Plasma proteins contain clotting agents that help wall off the pathogen and promote repair of tissues. • Macrophages release cytokines that tell the brain to release prostaglandins, which in turn stimulates fever production; moderate fevers inhibit pathogen growth.

43. Animation: Inflammatory Response CLICKTO PLAY

44. b a Mast cells in tissue release histamine, which then triggers arteriolar vasodilation (hence redness and warmth) as well as increased capillary permeability. Bacteria invade a tissue and directly kill cells or release metabolic products that damage tissue. e d a c b c Fluid and plasma proteins leak out of capillaries; localized edema (tissue swelling) and pain result. d Plasma proteins attack bacteria. Clotting factors wall off inflamed area. e Neutrophils, macrophages, and other phagocytes engulf invaders and debris. Activated complement attracts phagocytes and directly kills invaders. Fig. 10.7, p.181

45. Section 5 Overview of Adaptive Defenses

46. Overview of Adaptive Defenses • Adaptive immunity has three key features. • Adaptive immunity is the body’s third line of defense and has three defining features: • Adaptive immunity is specific; each B and T cell only recognizes one antigen. • Adaptive immunity is diverse; B and T cells collectively can recognize at least a billion different threats. • Adaptive immunity has memory.

47. Overview of Adaptive Defenses • Recognition of an antigen results in rapid cell division to produce huge numbers of identical B and T cells that recognize the stimulating antigen. • Some of these new cells are effector cells that can immediately destroy pathogens. • Others are memory cells, held in reserve for future battles against the same threat; memory cells are what make you “immune” to various pathogens.

48. Overview of Adaptive Defenses • B cells and T cells become specialized to attack antigens in different ways. • Both B and T lymphocytes arise in stem cells in the bone marrow. • B cells continue to develop within bone marrow. • T cells travel to the thymus to finish developing; T cells divide into two populations—helper T cells and cytotoxic (“killer”) T cells. • When mature, B and T cells can be found in the lymph nodes, spleen, and other lymphoid tissues where they remain “naive” until they recognize antigen.

49. Overview of Adaptive Defenses • B cells and T cells respond to pathogens in different ways. • B cells produce antibodies (proteins) and are responsible for antibody-mediated immunity. • T cells directly attack invaders; their response is called cell-mediated immunity. Figure 10.9

50. Red blood cells Platelets Monocytes, others Bone marrow Stem cells Thymus B cells T cells Organs of lymphatic system Foreign invasion B cells T cells Antibody-mediated immune response Cell-mediated immune response Fig. 10.9, p.182