1. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. Chapter 15 The Lymphatic System and Immunity

2. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 2 The Lymphatic System Lymph—fluid in tissue spaces that carries protein molecules and other substances back to the blood

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6. 6 The Lymphatic System Lymphedema—swelling (edema) of tissues caused by blockage of lymphatic vessels –Elephantiasis—severe lymphedema of limbs resulting from parasite infestation of lymphatic vessels

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12. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 12 The Lymphatic System Thymus –Plays central role in immunity –Produces T lymphocytes or T cells –Secretes hormone called thymosin –Atrophies in adults

13. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 13 The Lymphatic System Tonsils –Three around openings of mouth and throat Palatine tonsils (“the tonsils”) Pharyngeal tonsils (adenoids) Lingual tonsils –Subject to chronic infection –Enlargement of pharyngeal tonsils may impair breathing

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15. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 15 The Lymphatic System Spleen –Largest lymphoid organ in body –Located in upper left quadrant of abdomen –Often injured by trauma to abdomen –Surgical removal called splenectomy –Functions include phagocytosis of bacteria and old RBCs; acts as a blood reservoir –Splenomegaly—enlargement of the spleen

16. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 16 The Immune System Protects body from pathogens, foreign tissue, and cancer cells Nonspecific immunity –Skin—barrier to bacteria and other harmful agents

17. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 17 The Immune System Nonspecific immunity –Tears and mucus—wash eyes and trap bacteria –Inflammation attracts immune cells to site of injury, increases local blood flow, increases vascular permeability; promotes movement of WBCs to site of injury or infection

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22. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. Figure 21.13 Passive Active Humoral immunity Artificially acquired Injection of immune serum (gamma globulin) Naturally acquired Antibodies pass from mother to fetus via placenta; or to infant in her milk Artificially acquired Vaccine; dead or attenuated pathogens Naturally acquired Infection; contact with pathogen

23. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 23 The Immune System Specific immunity—ability to recognize, respond, and remember antigen Inborn immunity—inherited immunity to certain diseases from time of birth

24. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. Figure 21.7 Antigenic determinants Antigen- binding sites Antibody A Antibody B Antibody C Antigen

25. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. Figure 21.15 Inactivates by AntigenAntibody Fixes and activates Enhances Leads to Phagocytosis Chemotaxis Histamine release Inflammation Cell lysis Agglutination (cell-bound antigens) Precipitation (soluble antigens) Neutralization (masks dangerous parts of bacterial exotoxins; viruses) Complement Antigen-antibody complex Adaptive defensesHumoral immunity

26. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 26 Immune System Cells Phagocytes –Ingest and destroy foreign cells or other harmful substances via phagocytosis –Macrophages and DCs act as antigen- presenting cells (APCs) by displaying ingested antigens on their outer surface to trigger specific immune cells

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28. Copyright © 2010 Pearson Education, Inc. 1 2 3 Red bone marrow: site of lymphocyte origin Secondary lymphoid organs: site of antigen encounter, and activation to become effector and memory B or T cells Primary lymphoid organs: site of development of immunocompetence as B or T cells Lymphocytes destined to become T cells migrate (in blood) to the thymus and develop immunocompetence there. B cells develop immunocompetence in red bone marrow. Immunocompetent but still naive lymphocytes leave the thymus and bone marrow. They “seed” the lymph nodes, spleen, and other lymphoid tissues where they encounter their antigen. Antigen-activated immunocompetent lymphocytes (effector cells and memory cells) circulate continuously in the bloodstream and lymph and throughout the lymphoid organs of the body. Red bone marrow Bone marrow Thymus Lymph nodes, spleen, and other lymphoid tissues Immature lymphocytes Adaptive defenses Humoral immunity Cellular immunity

29. Copyright © 2010 Pearson Education, Inc. Primary response (initial encounter with antigen) Antigen binding to a receptor on a specific B lymphocyte (B lymphocytes with non-complementary receptors remain inactive) Proliferation to form a clone Activated B cells Plasma cells (effector B cells) Secreted antibody molecules Memory B cell— primed to respond to same antigen Clone of cells identical to ancestral cells Subsequent challenge by same antigen results in more rapid response Secondary response (can be years later) Memory B cells Plasma cells Secreted antibody molecules Adaptive defensesHumoral immunity Antigen

30. Copyright © 2010 Pearson Education, Inc. Time (days) Anti- bodies to A First exposure to antigen A Second exposure to antigen A; first exposure to antigen B Anti- bodies to B Primary immune response to antigen A occurs after a delay. Secondary immune response to antigen A is faster and larger; primary immune response to antigen B is similar to that for antigen A.

31. Copyright © 2010 Pearson Education, Inc. (a) B cell (being activated) MHC II protein of B cell displaying processed antigen IL- 4 and other cytokines Helper T cell CD4 protein T cell receptor (TCR) Activated helper T cell 1 2 T H cell binds with the self-nonself complexes of a B cell that has encountered its antigen and is displaying it on MHC II on its surface. T H cell releases interleukins as co-stimulatory signals to complete B cell activation. T H cell help in humoral immunity

32. Copyright © 2010 Pearson Education, Inc. Class II MHC protein Class I MHC protein APC (dendritic cell) IL-2 CD4 protein CD8 T cell Helper T cell CD8 protein (b) 1 2 Previously activated T H cell binds dendritic cell. T H cell stimulates dendritic cell to express co-stimulatory molecules (not shown) needed to activate CD8 cell. 3 Dendritic cell can now activate CD8 cell with the help of interleukin 2 secreted by T H cell. T H cell help in cell-mediated immunity

33. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 33 Immune System Cells –Development of B cells Second stage—inactive B cell develops into activated B cell –Initiated by inactive B cell’s contact with antigens, which bind to its surface antibodies, plus signal chemicals from T cells –Activated B cell, by dividing repeatedly, forms two clones of cells—plasma (effector) cells and memory cells –Plasma cells secrete antibodies into blood; memory cells are stored in lymph nodes –If subsequent exposure to antigen that activated B cell occurs, memory cells become plasma cells and secrete antibodies

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35. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 35 Immune System Cells –Functions of T cells—cell-mediated immunity Cytotoxic T cells—kill infected or tumor cells by releasing a substance that poisons infected or tumor cells Helper T cells—produce chemicals that help activate B cells Regulatory T cells—release chemicals to suppress immune responses

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37. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 37 Hypersensitivity of the Immune System Inappropriate or excessive immune response Allergy—hypersensitivity to harmless environmental antigens (allergens) –Immediate allergic responses usually involve humoral immunity –Delayed allergic responses usually involve cell-mediated immunity

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40. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 40 Hypersensitivity of the Immune System A healthy immune system works efficiently to fight off disease. In someone with an autoimmune disorder, the immune system wrongly identifies healthy tissues as foreign and tries to destroy them. There are over 80 known types of disorders, affecting different areas of the body – from joints and muscles to skin and blood and organs. Among the most common autoimmune conditions are type 1 diabetes, multiple sclerosis, Crohn's disease, rheumatoid arthritis and psoriasis. There is no cure, but medication and a healthy lifestyle can help manage these conditions while researchers continue to look for new treatment approaches.

41. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 41 Hypersensitivity of the Immune System Isoimmunity—excessive reaction to antigens from another human –May occur between mother and fetus during pregnancy –May occur in tissue transplants (causing rejection syndrome)

42. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 42 Immune System Deficiency Congenital immune deficiency or immunodeficiency (rare) –Results from improper lymphocyte development before birth –Severe combined immune deficiency (SCID)—caused by disruption of stem cell development

43. Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 43 Immune System Deficiency Acquired immune deficiency –Develops after birth –Acquired immunodeficiency syndrome (AIDS)—caused by HIV infection of T cells