1. Specific Immunity Destroy specific antigens that invade the body

2. Specific Immune Responses Take several days to activate Have immunological memory 2 types: Cell-mediated immunity Antibody-mediated immunity

3. Meet the players… MHC APCs Lymphocytes

4. Major Histocompatibility Complex Group of closely linked genes – polymorphic Distinguish self from non-self Genes encode MHC antigens Differ in chemical structure, function and tissue distribution

5. 3 Types of MHC genes: Class I – encode glycoproteins found on surface of most cells of body Class II - glycoproteins expressed on APCs Combine with foreign antigens Class III – secrete proteins involved in immune response Complement system

6. Antigen-Presenting Cells (APCs) Include: Macrophages Dendritic cells B cells Inactive until their receptors recognize PAMPs on pathogen Display foreign antigens + own on cell surface

7. APCs cont. APCs ingest pathogen Break down most of it Remaining pieces of antigens displayed on cell surface along with self-molecules Signaling molecules are released Present antigen to T cells

8. Lymphocytes 3 main types: Natural Killer Cells T cells B cells All 3 develop from stem cells in bone marrow Large #s of lymphocytes found in lymph organs

9. Memory T cell B

10. Lymphocytes, cont. T cells Travel to site of infection Attack foreign cells & own infected cells B cells Mature into plasma cells Plasma cells produce antibodies

11. T cells Mature in the thymus gland Become immunocompetent Develop surface proteins w/ specific receptor sites Must recognize self-antigens Must bind with foreign antigens If can’t distinguish between self & non-self, undergo apoptosisapoptosis http://www.bio.davidson.edu/courses/Immuno logy/Flash/Main.html http://www.bio.davidson.edu/courses/Immuno logy/Flash/Main.html

13. Types of T cells Cytotoxic T cells (T C cells) Recognize and destroy foreign antigens including Grafts Virus-infected cells Cancer cells Helper T cells (T H cells) Regulatory Secrete cytokines to activate B cells and macrophages

14. Cell-Mediated Immunity APCs T cells

15. T C cells Have CD8 glycoproteins 50,000+ receptors that bind to 1 specific antigen Recognize antigen-class I MHC complex T H cells Recognize antigen-class II MHC complex Less than 1 in 10,000 T cells have same antigen specificity

16. T cell activation Cells must be activated before they can respond to pathogen Activation requires: Properly presented antigen Co-stimulatory signal Released by APC Interleukin signal Released from macrophages and lymphocytes

17. After activation… T C cells: T C cells Enlarge and clone many T C cells specific for that antigen Leave lymph nodes and go to infection Combine with antigen and destroy cells within seconds Secrete perforins and granzymes Release and find new antigens to destroy

18. After activation, cont… T H cells: T H cells Clone Release cytokines to attract macrophages and T C cells Also play a role in antibody-mediated immunity Both T C cells & T H cells produce memory cells for secondary immunity

20. Summing up Cell-Mediated ImmunitySumming up Cell-Mediated Immunity: Pathogen infects body cell Cell breaks up pathogen and displays foreign antigen along with MHC-class I or II antigen on surface Specific T cells activated and clone T C cells leave lymph, go to infection, and destroy cell T H cells release cytokines to stimulate T C cells and macrophages; also trigger antibody-mediated immunity

21. Antibody-Mediated Immunity B cells

22. B cell activation APC presents antigen to T H cell: Multiple chemical signals sent back & forth T H cell becomes activated **B cell can be an APC Activated T H cell releases interleukins which, along with antigen, activates B cell http://bcs.whfreeman.com/thelifewire/content/ chp18/1802004.html http://bcs.whfreeman.com/thelifewire/content/ chp18/1802004.html

25. After activation… B cell divides by mitosis Clone of identical cells Specific for the activating antigen B cells mature into plasma cells Secrete specific antibodies Plasma cells remain in lymph node but secrete antibodies into lymph/blood

26. Antibody (aka Immunoglobulin) Structure:

27. Types of Immunoglobulins: 5 classes of antibodies based on amino acid sequences IgG 75% of human circulating antibodies Along with IgM, interacts with macrophages and activates complement system Defend against blood pathogens – viruses, bacteria, some fungi

28. Immunoglobulins,cont. IgA – mucus, tears, saliva, breast milk Prevents bacteria and viruses from attaching to epithelium Defends against inhaled or ingested pathogens IgD Found on surface of B cells Helps activate B cells Aids in maturation of B cells IgE Plays a role in allergic response Immune response to parasitic worms

29. How do antibodies work?? Highly specific Binds to specific part of antigen Epitope Activates processes that destroy antigen Labels antigen for destruction, it doesn’t destroy antigen itself

31. Usu. Several antibodies bind with several antigens creating an antigen-antibody complex May inactivate pathogen or toxin Prevent binding to host

32. Antigen-antibody complex stimulates phagocytosis

33. IgG and IgM antibodies work mainly through complement system Coat surface of pathogen to increase phagocytosis Stimulate release of histamine Attracts phagocytes Complement proteins destroy the pathogen

34. Summing Up Specific Immunity http://www.learner.org/channel/courses/bi ology/archive/animations/hires/a_hiv1_h.h tml

35. Memory Responsible for long-term immunity Memory T cells Memory B cells Primary immune response Occurs when 1 st exposed to antigen Antibodies appear in 3-14 days After recognition, antibodies build up for several days then decline

36. Secondary immune response Memory B cells persist for many years When exposed to antigen again, secondary response is much more rapid Often don’t “get sick” because response is so quick Booster shots given to trigger secondary immune response

37. Active vs. Passive Immunity Active – body develops after exposure to antigen Natural – pathogen enters naturally Artificial – pathogen introduced ex. vaccine Passive – antibodies given; borrowed immunity Natural – mother to baby Artificial –injection with gamma globulin