Immunity refers to the capability of the body to resist organisms and toxins that can damage tissues and organs. There are two types of immunity: innate immunity, which includes the skin, gastric acids, and immune cells; and acquired immunity, also called adaptive immunity, where the body produces antibodies and activated immune cells in response to specific pathogens. Acquired immunity involves lymphocytes that mature in the thymus and bone marrow and are stored in lymphoid tissues.

1. IMMUNITY The capability to resist any organism or toxin that tend to damage the tissues and organs.

2. Immunity Innate = ability to resist damaging organisms and toxins skin, gastric acids, tissue neutrophils and macrophages, complement, NK cells Acquired = specific humoral ----> circulating antibodies(B-cell) cellular ----> activated cells(T-cell mediated)

4. Preprocessing of the T and B lymphocytes Thymus gland preprocesses the T lymphocytes Liver and bone marrow preprocess the B lymphocytes

5. Lymphoid tissue

6. Millions of specific types of lymphocytes are stored in the lymphoid tissue. All the different lymphocytes that are capable of forming one specificity of antibody or T cell are called a ‘clone of lymphocyte’.

7. Sequence Dormant lymphocytes Invasion of body by foreign antigen Phagocytosis by macrophages Presentation of antigen to lymphocytes

8. Antigen An antigen is a substance that can induce an immune response when introduced into an immunocompetent host and that can react with the antibody produced from that response.

9. Bone Marrow Pre-B Cell Pre-T Cell T-Cell T8-supressor T4-helper B-Cell Plasma Cell IgG IgA IgM IgD IgE Interactions between T- and B-Cells

10. Humoral immunity and Antibodies

11. Formation of antibodies by plasma cells Dormant B lymphocyte Exposure to a specific antigen Macrophage plays role in the activation process Helper T cells also contribute in this activation process

12. These B lymphocytes enlarge to form lymphoblast. Further diferentiate into plasmablast The mature plasma cells(antibody factories) then produce gamma globulin antibodies .

13. Formation of Memory cells-difference between primary and secondary response

14. virgin cells first exposure to antigen second exposure to antigen activated cells memory cells Formation of Activated and Memory Cells Copyright © 2006 by Elsevier, Inc.

16. self-antigens death Central lymphoid organ Peripheral lymphoid organ stimulation self-antigens death inactivation Loss of Antigens to Self

17. Antibodies antigen binding site hinge region light chain heavy chain Fab fragment Fc fragment IgA, IgD, IgE, IgG, IgM

18. IgM Antibody

19. Antibodies IgG - 80% total, cross placenta, opsonization IgM - first produced, 10-15% total, activate complement IgD - not known, may help CD4 Th IgA - body fluid, tears, bronchiole secretions, saliva IgE - allergic reactions, histamine release

20. Mechanism of action of antibodies Direct Action Complement System

21. Direct action of antibodies on invading agents AGGLUTINATION PRECIPITATION NEUTRALIZATION LYSIS

22. Complement System Series of ~ 20 proteins Activated by microorganisms Will coat the microorganisms Present normally among plasma proteins The enzyme precursors can be activated by the so called ‘ classical pathway ’ s

24. complement bacteria phagocyte bacteria 2 . chemotaxis 1 . lysis 3 . opsonization Functions of Complement Activation Copyright © 2006 by Elsevier, Inc.

25. Antibody-Activated Phagocytosis Fc receptor bacterium opsonization

26. IgE and Histamine Release IgE receptor histamine vesicles binding of IgE to Fc receptor antigen antigen release of histamine binding of antigen

27. Thank You

28. T-cells Act over a short range Interact with another cell in body Can kill or signal other cell Only recognize antigen when presented on surface of target cell

29. T-cells Cytotoxic Cells kill infected cells Helper Cells (two types) activate macrophages and B-cells Suppressor Cells regulate activity

30. TH 1 TH 2 TC LGL B Antibody Production Virally infected cell and some tumor cells Antigen presentation Antigen presentation activation activation cytotoxicity macrophage T-Cell Function

31. Mhc-molecules MHC-I present foreign peptides to cytotoxic cells MHC-II present foreign peptides to helper cells

32. CYTOTOXIC T-CELLS HELPER T-CELLS Tc Th Class I MHC Class II MHC foreign protein infected target cell antigen- presenting cell Mhc-molecules

33. Helper T-cells Helper T-Cells recognize foreign antigen bound to MHC-II proteins on surface of antigen-presenting cells Helper T-Cells stimulate macrophages and B-cells Two signals are required for activation of Helper T-Cells

34. Activation of Helper T-cells Th antigen- presenting cell signal 1 signal 2 activation signal 2 is chemical (interleukin-1) or membrane bound molecule CD4 antigen

35. Activation of Helper T-cells Th antigen- presenting cell signal 1 signal 2 Th Il-2 receptor Il-2 Th Th proliferation CD4

36. Cytotoxic T-cells Cytotoxic T-Cells recognize viral protein fragments on surface of infected cells. Cytotoxic T-Cells induce infected cells to kill themselves Bind to infected cells Induce cell death Punch holes in cell membrane

37. Cytotoxic T-cells Class I MHC Tc infected target cell CD8 Perforin discharge

38. Natural Killer destroy virus-infected cells do not express antigen specific receptors cells with low levels of MHC I induce cells to undergo apoptosis

39. TC TCR CD8 MHC Class I Inhibitory receptor NK Target No MHC Class I NK receptor