Chapter 20

1. Chapter 20 Defenses Against Disease: The Immune System

2. Outline • Functions of the Immune System • Definitions • Primary & Secondary Immune Organs • Nonspecific Defenses: Aid Immune System • Barriers to Entry • Inflammatory Reaction • Complement System • Specific Defenses: The Immune Response • B-lymphocytes: Antibody-Mediated Immunity • T-lymphocytes: Cell-Mediated Immunity • Induced vs. Passive Immunity

3. Functions of The Immune System • The immune system functions to defend the body against all attackers including viruses, bacteria, and cancer cells. • Protects “self” from “non-self”. • Immunity is the ability to react to antigens so that the body remains free of disease. • Disease is a state of homeostatic imbalance. • Disease can be due to infection or failure of the immune system.

4. Functions of The Immune System (Con’t) • Definitions • Antigen:Piece or part of a foreign attacker such as a piece of protein or cell membrane. • Antibody:Special protein produced by the immune system to bind specifically to antigens. Antibody shape fits like a glove to the surface shape of the antigen. Helps to remove attacker from the body.

5. Primary Immune Organs • Immune system is network of organs, tissues, cells, and cell produces. • Principal cells are the lymphocytes, aided and assisted by neutrophils, macrophages. • Two types: B lymphocytes and T lymphocytes • Primary Immune Organs: Lymphatic organs contain large numbers of lymphocytes. • Red Bone Marrow: Source of B & T lymphocytes; B lymphocytes mature here; move to lymph nodes • Thymus Gland: T lymphocytes move here from bone marrow; mature here; move to lymph nodes.

6. Secondary Immune Organs • Secondary Immune Organs: Secondary lymphatic organs are places where lymphocytes encounter and bind with antigens. • Spleen. • Lymph nodes: In the lymphatic system • Tonsils: Lymphatic tissue at back of mouth • Peyer’s patches: Lymphatic tissue in intestines

7. Lymphatic Organs

8. Nonspecific Defenses: Aid Immune System • Barriers to Entry. • Skin. • Oil gland secretions. • Ciliated cells and mucous membranes of the respiratory tract. • Stomach. • Acid in stomach; pH 1-2.

9. Nonspecific Defenses: Aid Immune System • Inflammatory Reaction. • Tissue damage causes tissue cells and mast cells to release chemical mediators. • Histamine and kinins. • Capillaries dilate and become more permeable. • Skin reddens and becomes warm. • Proteins and fluids escape from tissue. • Swelling.

11. Nonspecific Defenses: Aid Immune System • Inflammatory Reaction. • Proteins and fluids escape from tissue and cause swelling. • Swelling stimulates free nerve endings, causing the sensation of pain. • Neutrophils and monocytes migrate to site of injury; engulf pathogens. • Monocytes become macrophages; engulf pathogens; spit out antigens.

13. Nonspecific Defenses: Aid Immune System • Inflammatory Reaction Movies 1. Rolling Leukocytes 2. Lymphocyte Homing 3. Chemotaxis of Neutrophils 4. Neutrophil Chase

14. Nonspecific Defenses: Aid Immune System • Complement system: Group of proteins in blood that help to destroy pathogens. • Complement proteins are activated when antibodies coat pathogens in the body. • They form membrane attack complex that knocks holes in the membrane of pathogen. • Complement coated pathogens also attract neutrophils and macrophages.

15. Complement System

16. Specific Defenses: The Immune Response • Specific defenses respond to antigens. • Lymphocytes recognize an antigen due to antigen receptors whose shape allows them to combine with a specific antigen. • Immunity is primarily the result of the action of B lymphocytes and T lymphocytes.

17. Specific Defenses: The Immune Response • B-lymphocytes and antibody-mediated immunity. • Main end products: Antibodies and memory B-lymphocytes. • Antibodies bind to pathogens; they help complement to work; help neutrophilsand macrophages find and engulf them.

19. Specific Defenses: The Immune Response • B-lymphocyte Review • Provide antibody-mediated immunity against bacteria. • Produced and mature in bone marrow. • Reside in spleen and lymph nodes. • Circulate in blood and lymph. • Directly recognize antigen and then undergo clonal selection. • Clonal expansion produces antibody-secreting plasma cells and memory B cells.

20. Structure of most common antibody: IgG

21. Specific Defenses: The Immune Response • T-lymphocytes and cell-mediated immunity. • Main end products: Cytotoxic T-lymphocytes and memory T-lymphocytes. • Cytotoxic T-lymphocytes bind antigen-bearing, pathogen infected cells and destroy them; they also attack cancer cells and destroy them.

24. Specific Defenses: The Immune Response • T-lymphocyte Review • Provide cell-mediated immunity. • Produced in bone marrow, mature in thymus. • Antigen must be presented in groove of HLA molecule. • Cytotoxic T cells destroy nonself protein-bearing cells. • Helper T cells secrete cytokines that control the immune response.

25. Induced Immunity • Active Immunity. • Immunization involves use of vaccines. • Contain an antigen to which the immune system responds. • Primary response. • Secondary (booster) response. • Dependent upon the presence of memory B and T cells capable of responding to lower antigen doses.

26. Passive Immunity • Passive immunity occurs when an individual is given prepared antibodies. • Temporary. • No memory cells.

27. Immunity Side Effects • Allergies. • Hypersensitivities to substances (allergens) that would ordinarily not harm to the body. • Immediate allergic responses are caused by IgE. • Delayed allergic responses are initiated by memory T cells at the site of allergen contact.

28. Tissue Rejection and Autoimmune Diseases • Tissue rejection occurs because antibodies and cytotoxic T cells begin to destroy foreign tissues in the body. • Immune system working correctly. • Autoimmune diseases occur when antibodies mistakenly attack the body’s own cells as if they bear foreign antigens. • Immune system working incorrectly.

29. Need to Know • Functions of Immune System • Defense against “non-self”. • Bacteria • Viruses • Cancer Cells • Generate Immunity • To remain free of disease. • Definitions • Antigen: Part or piece of foreign attacker, usually a piece of protein or cell membrane • Antibody: Special protein made to fit antigen like a glove

30. Need to Know (Con’t) • Nonspecific Defenses: Aid Immune Response • Inflammatory Reaction • Results: Neutrophils, macrophages engulf and kill pathogens and spit out antigens • Specific Defenses: The Immune Response • B-lymphocytes & antibody mediated immunity • Main end product: Antibodies & memory B-lymphocytes • Antibodies help macrophages and complement to remove pathogens • T-lymphocytes & cell mediated immunity • Main end product: Cytotoxic T-lymphocytes & memory T-lymphocytes • Attack and kill antigen-bearing pathogen infected cells & cancer cells

31. Need to Know (Con’t) • Induced vs. Passive Immunity • Induced (Active) Immunity: Addition of vaccine to body stimulates immune system; helps maintain memory cells • Passive Immunity: Antibodies given to person; temporary; no memory cells • Complement System • Works with antibodies to help kill pathogens like bacteria • Binds and generates holes in bacteria

32. Need to Know (Con’t) • Primary & Secondary Immune Organs • Primary • Red Bone Marrow: both B & T-lymphocytes • Thymus Gland: T-lymphocytes mature here • Secondary: Lymphatic tissue throughout the body • Spleen • Lymph nodes • Tonsils • Peyer’s Patches