1. Lecture 14 Immunology: Adaptive Immunity

2. Principles of Immunity Naturally Acquired Immunity- happens through normal events Artificially Acquired Immunity- by immunization Active Immunity- result of an immune response in an individual exposed to antigen Passive Immunity- occurs naturally during pregnancy; or antibodies from one person transferred to another Innate Immunity- Immunity that we are born with

3. Figure 17.1

4. Adaptive Immunity Different from Innate Immunity Matures throughout life Develops specific immune response as invaders are encountered Has a “memory” Must discriminate between self and dangerous (non-self) Very complex system

5. Adaptive Immunity Four important attributes: Specificity- immune system responds specifically to epitopes Tolerance of “self”- Immune system does not respond to “self” Minimal “self” damage- do not damage “self” Immunologic Memory- Once exposed will not get sick with same disease again

6. Overview of Adaptive Immunity Uses two basic strategies 1.Humoral Immunity - works to eliminate antigens that are extracellular 1.Cellular Immunity - deals with antigens within host cell

8. Humoral Immunity

9. Overview of Humoral Immune Response Mediated by B-lymphocytes or B-cells Encounter antigen- differentiate and proliferate into plasma cells and memory B cells Plasma cells make Y-shaped molecules called antibodies Antibodies bind to antigens, providing protection to host

11. Antibodies Globulin protein molecules- also called Immunoglobulins Secreted by B-cells Y-shaped 5 different classes: –IgM, IgG, IgA, IgE, IgD

12. Figure 17.3 - Overview

13. Table 17.1

14. Immunoglobulin M (IgM) First class produced during primary immune response to antigen It is in pentamer form Large- does not cross from blood to tissues

15. Immunoglobulin G (IgG) 80-85% of total Ig’s in people over age 2 Provides longest term protection of all antibodies First and most abundant Ig, during secondary response Can cross placenta from mother to fetus- helps to protect fetus and new-born Also present in colostrum- first breast-milk produced

16. Immunoglobulin A (IgA) Important in mucosal immunity In breast milk- protects infants from intestinal pathogens Immunoglobulin D (IgD) -Accounts for less than 1% of Ig’s -Involved in development and maturation of antibody response

17. Immunoglobulin E (IgE) Barely detectible in blood Bound tightly to basophils and mast cells Bound IgE, allows these cells to detect and respond to antigens These cells release histamine, cytokines, and other chemicals that contribute to immune response

18. Allergies Basophils and mast cells release their chemicals when IgE binds to normally harmless material such as pollens Leads to immediate reaction- coughing, sneezing, and muscular contractions Response can be life threatening

19. Primary and Secondary Responses of Antibodies

20. Protective Outcomes of Antibody- Antigen binding A. Viral Inhibition: virus preventing it from attaching to cell B. Neutralization: make toxins unable to bind to cells C. Opsonization: antibodies bind to antigen and facilitate attachment of phagocytic cells

21. D. and E. Agglutination and Precipitation: antibodies bind to antigen and get them into clumps, then one big “mouthful” for phagocyte F. Phagocytosis: Fc portion of antibody encourages phagocytosis Complement Activation: binding of antigen to antibody can trigger one pathway of complement cascade

24. B-cells and Antibody Response B-cell receptor binds to antigen One of two things happen: –B-cell needs confirmation by T-cell to begin responding –B-cell does not need confirmation by T-cell to begin responding

25. When B-cell does not need confirmation from T-cell B-cell receptors bind epitopes B-cells respond by proliferating, producing antibody and differentiating into memory B-cells

26. Fi When B-cell needs confirmation from T-cell gure 16.9

27. Cellular Immunity

28. Overview of Cellular Immunity Mediated by T lymphocytes or T-cells Has receptor similar to B-cells Antigen must be presented to it by another cell Two types: –T-cytotoxic cells- destroy infected cells –T-helper cells- activate macrophages

30. T-cells: Antigen Recognition and Response Have multiple copies of receptor on surface that recognizes specific antigen DO NOT produce antibody DOES NOT interact with free antigen Antigen must be presented by another cell, by MHC Two types of T-cells: –T-cytotoxic –T-helper

31. Figure 16.15

32. T-cytotoxic cells Also called CD8 T cells Once activated, induce apoptosis in “self” cells infected with virus; destroy cancerous host cells Distinguish infected “self” cells, because these cells present peptides on surface in MHC class I molecule

33. Figure 17.10 - Overview

34. T-helper cells Also called CD4 T-cells Antigen presenting cells, present antigen to T-helper cells in MHC class II If recognize antigen presented as foreign, activate macrophages, release cytokines that recruit other cells of immune system, stimulate NK cells, activate B cells

35. Figure 17.9 - Overview (1 of 4)