Chapter 24- The Immune System

1. Chapter 24- The Immune System • Active immunity • Allergen • Allergies • Anaphylactic shock • Antibody • Antigen • Antigen receptors • Antigen-binding site • Antigenic determinants • Antigen-presenting cells • Antihistamine • Autoimmune diseases • B cells • Cell-mediated immunity • Clonal selection • Complement proteins • Cytotoxic T cells • Helper T cells • Histamine • Humoral immunity • Immune system • Immunity • Immunodeficiency diseases • Inflammatory response • Interferons • Lymph • Lymphatic system • Lymphocytes • Macrophages • Major histocompatibility complex • Mast cells • Memory cells • Monoclonal antibodies • Monocytes • Natural killer cells • Neutrophils • Nonself molecules • Passive immunity • Perforin • Plasma cells • Primary immune response • Secondary immune response • Self protein • T cells • Vaccination • Vaccine

2. Immune system • Protects the body by recognizing and attacking specific kinds of pathogens and cancer cells • There are both nonspecific and specific responses against infection

3. 1st line of defense is nonspecific Nonspecific = (can’t distinguish a certain pathogen) • Intact skin- barrier that pathogens can’t penetrate • Acids secreted by glands in skin- inhibit microbe growth • Sweat, saliva, tears- contain lysozyme- an enzyme that attacks bacterial cell walls • Digestive and respiratory systems- guarded by mucous membranes (b/c they are exposed to env) • Stomach acid- kills bacteria • Hair in nostrils- filters air • Mucous in respiratory system traps particles and cilia sweep them out

4. Nonspecific defense cells • Neutrophils, monocytes and macrophages- engulf bact and viruses • Natural killer cells- attack cancer cells and infected body cells (especially those that harbor viruses)

5. Proteins also attack microbes or impede reproduction • Interferons- proteins that are produced by cells that are infected by a virus to help other cells resist virus • Nonspecific, short term, can be used to treat certain cancers • Complement proteins- circulate in plasma, activated by immune system or microbes, stick to surfaces for macrophages to notice, cut holes in cells, amplify nonspecific responses

6. Inflammatory response

7. Inflammatory response • Major component of nonspecific defense • red, swollen, warm “inflamed” –due to increase in blood flow, fluid and cells • Damaged skin releases chem signal (histamine) • It induces blood vessels to dilate and become leaky • Blood flow to area increase, plasma moves to interstitial fluid • Other chem’s attract phagocytes • Results: disinfect area, engulf bacteria • Clotting proteins- seal off infected region • Response can be local or systemic (WBC’s increase, fever, high fever, low BP-septic shock)

8. The Lymphatic System • Returns tissue fluid to circ system and fight infection • Consists of: vessels, lymph nodes, tonsils, adenoids, appendix, spleen, bone marrow, thymus • Involved in: nonspecific and specific resistance to infection • System is where fluid that has left circ system returns to, happens by diffusion • Infection fighting occurs in lymph nodes and other vessels which are packed with WBC’s • Sometimes they become swollen when fighting infection

9. The Lymphatic System

10. Specific Immunity • Immunity- resistance to specific invaders • Active- when antigens enter body (getting sick/a shot) • Passive- antibodies are passed (fetus from placenta, sometimes when travelling to other countries) • Antigen- “antibody generating”- elicits immune response • Molecules on surfaces of cells • Antibody- protein in blood plasma that attaches to particular antigen and help counter its effect *****has a good memory*****

11. Lymphocytes • White blood cells • Originate in bone marrow • Spend most of their time in tissues and organs of lymphatic system • Produce specific immune responses • Response to antigens in 2 ways:

12. Mature in bone marrow= B cells Humoral immunity Secretes antibodies Can be transferred passively (injecting antibodies) Mature in thymus =T cells Cell-mediated immunity Attacks infected body cells Promotes phagocytosis and stimulates B cells (so T cells are involved in both) Can be transferred passively (injecting T cells) Lymphocytes • Antigen receptors- molecules on cells surface, bind to antigen • 100mil to 100bil different kinds of B and T cells!

13. Lymphocytes

14. Antigens • Most are proteins or polysaccharides • Antigenic determinants- region that antibody recognizes • Site on antibody (antigen-binding site)- recognizes determinant • *complementary shape

15. Antigens • Activate lymphocytes to multiply that are specific to the antigen- clonal selection • Effector cells produced secrete antibodies • This happens with B cells and T cells

16. Primary Immune Response • 1st time lymphocytes are exposed to antigen and clonal selection happens • Takes a few days before lymphocytes are activated

17. Secondary Immune Response • After 2nd exposure to same antigen • Produces very high antibody levels, lasts longer • Each antigen exposure triggers clonal selection • Cells of the clone include: • Memory cells- last for decades, remain in lymph nodes, when activated-trigger secondary response, multiply quickly • Effector cells- produce antibodies

18. Humoral vs. Cell-mediated Immunity

19. Humoral Immunity • In body fluids • Effector cells produced during clonal selection are called plasma cells • Plasma cells then secrete antibodies

20. Antibodies • 2 heavy chains and 2 light chains bonded together • 2 functions: recognize and bind to antigen & neutralize the antigen • Structure allows function • Antigen-binding sites in V region • Mark antigens for elimination • Binding creates antigen-antibody complex

21. Methods for antigen inactivation: • Neutralization- antibodies block antigens from binding with cells, phagocytes engulf complex • Agglutination- “clumping” – clumps invaders together making it easier for phagocytes to capture • Precipitation- link antigen molecules together and they precipitate out of solution as solids, easily engulfed • Activation of complement proteins by antigen-antibody complex- proteins open holes in plasma membrane, cell lyses

23. Monoclonal antibodies • Antibody secreted by a clone of cells that’s specific for an antigen • Ex: pregnancy test- binds to hormones, STD test-binds to bacteria

24. Cell-mediated Immunity • T cells respond to antigens on body’s own cells • Cytotoxic T cells- attack infected body cells • Helper T cells- help activate cytotoxic T’s and macrophages, and stimulate B’s to produce antibodies • Antigen-presenting cells (APC’s) – present antigens to helper T’s- triggering pathway to activate helper T’s

25. When a T cell is activated: • Grow and divide, producing more helper T and memory T cells • Stimulate cytotoxic T’s • Bind to infected cells and form holes in membrane • Activate B cells • Cytotoxic T cells also can recognize changes in membranes of cancerous cells and destroy them

26. Immune system depends on our molecular fingerprint • Recognizes “self” and “non-self” • What if that doesn’t work?

27. Immune System Disorders • Autoimmune disease- immune system attacks body’s own cells • MS, lupus, insulin-dependent diabetes

28. Immune System Disorders • Immunodeficiency disease- when a component of the system is lacking • Can be caused by physical and emotional stressors • AIDS, SCID, Hodgkins disease • HIV virus destroys helper T cells • Allergies- overreaction of the immune system • Antigens that cause allergies are called allergens