Dr.M.B.Bhat.

1. IMMUNITY Dr.M.B.Bhat.

2. Immunity Is the resistance of the body against almost all types of organisms or toxins that tend to damage the tissues & organs. • Types-- Natural (innate) immunity Acquired immunity

4. Natural/ innate/ nonspecific immunity • It is present since birth, prevents entry of micro organisms into the body. • It is the first line of defense against any pathogens. • Mechanisms involved— • Phagocytic activity of WBCs • Acid in the stomach • Lysozymes present in the tears and saliva • skin

5. IMMUNITY CLASSIFICATION

6. Tyccpes of immunity

7. Acquired immunity /specific immunity • If the invaders overcome the natural immune system, then the acquired immune system comes into play. • It is the resistance developed against a specific foreign body, so its also known as specific immunity. • It’s the most powerful immune mechanism

8. Acquired immunity • Acquired immunity is the product of the body’s lymphocyte system • Lymphocytes are located extensively in the lymph nodes and also special lymphoid tissue such as spleen, submucosal areas of GIT, bone marrow • Although most of the lymphocytes look alike, these cells are divided---- two major population

9. Types of Acquired immunity 1. T lymphocytes- Cellular immunity or T-cell immunity----- by ------ T-Cells 2. B lymphocytes-Humoral or B-cell immunity----- by ---------Antibodies.

10. \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ Processing of T-Lymphocyte precursors from the bone marrow enters the thymus gland form T-lymphocytes Preprocessing is shortly before birth & few month after birth Types— Helper T cell or inducer T cell Cytotoxic T cell or Killer Tcell Suppressor T cell Memory T cell

11. Processing of B- lymphoctes Precursors enter fetal liver and after birth in bone marrow and get transformed into B-lymphocytes After preprocessing ,the B & the T lymphocytes migrate and stay in lymphoid tissues Processing occurs during fetal & neonatal life.

12. Cell Mediated Immunity T-cells T-lymphocytes Antigen CLONE Stem cell Thymus Lymph node B-lymphocytes Fetal liver Bone marrow Antigen Antibodies Humoral Immunity

13. Schematic chart to show the role of T and B lymphocytes in immunity Suppressor T cell

14. Development of cell mediated immunity It develops when an antigen from the invading micro organism is exposed to the T-lymphocytes ------ Helper, cytotoxic & supressor T cells The exposure or presentation of antigen to the lymphocytes is done by Antigen presenting cells Macrophages: Large phagocytic cells which digest invading organisms to release the antigen------ present in all lymphoid tissues

15. Development of cell mediated immunity

16. Cell mediated immunity • The antigenic products activate the helper T cells • Activated helper T cells in turn brings about activation of B-lymphocytes • Activated helper T cells causes activation and proliferation of cytotoxic lymphocytes, & supressor t cells

17. Schematic chart to show the role of T and B lymphocytes in immunity Suppressor T cell

18. Helper T cell— • Promotes various activities of immune system; it stimulates other T cells and B cells.

19. Cell mediated immunity Humoral Immunity

20. Cell mediated immunity • Cytotoxic T cell— • The activated T cells comes into circulation to destroy the invading organism---- Killer cell

21. Cytotoxic T cell • Recognize antigens on the surface of all cells • Kill host cells that are infected with viruses or bacteria. • Recognize and kill cancer cells. • Recognize and destroy transplanted tissue. • .

22. Cell mediated immunity • Suppressor T cells— • Suppresses the activities of cytotoxic T cells and prevents it from destroying the body’s own tissue. • It also suppresses helper T cells.

23. Cell mediated immunity • Memory T cell— • Some of the activated T cells do not enter the circulation but migrate to various lymphoid tissue, and get activated when body is exposed to the same antigen again. • The response is immediate and more powerful. • Specificity of T cells—Each T cell gets activated by only one type of antigen.

24. Humoral immunity • Upon entry of antigen, the B lymphocytes can bind with the antigen directly. • They are transformed into two types memory B cells and “plasma cells”.

25. Humoral immunity • The plasma cells secrete large quantity of antibodies which are gamma globulin in nature • Antibodies are secreted into the lymph and carried to the circulating blood

26. Memory B cells Some of the B-lymphocytes activated by the antigen do not form the plasma cells Remain inactive until the body is exposed to same antigen for the second time--- secondary response.

27. B- cell Differentiation

28. The antibodies produced on first exposure takes longer time • On second exposure, the antibody produced is faster • This forms the basic principle of vaccination against infection.

29. Primary/ secondary response

30. Stages of Humoral immune response • 1. Antigen processing and presentation • 2.Recognition of antigen by lymphocytes • 3.Lymphocyte Activation • 4. Production of antibodies • 5. Inactivation of antigen or attack phase

31. Structure of immunoglobulin

32. Types of Antibodies • IgG(70%), • IgA(22%), • IgM(7%), • IgD IgE

33. Mechanism of action of antibodies • Direct action– • Agglutination • Precipitation • Neutralization • Lysis

35. Action of antibody through complement system • The “complement system ” is a collective term to describe a system of about 30 different proteins • This action is stronger than direct action, as the complement system accelerates the fight against invading organism.

36. Action of antibody through complement system • The principal actors in the Complement system are 11 plasma enzymes named C1 to C9,B & D. • These enzymes are in inactive form and get activated by 2 ways--- • Classical pathway • Alternate pathway

37. Classical pathway— • Activated by antigen antibody reactions • C1 binds with the Ag & Ab complex and triggers a series of events to activate other enzymes. • Multiple end products are formed with important effects.

38. Pathway of complement system Opsonization of bacteria Ag+Ab complex C1 C1- C4 + C2 C42 + C4a C3 C3b +C3a (Microorganism+B &D) C5 C5b+C5a C6 +C7 C5b67 C8 + C9 C5b6789 Lysis of cells Activate mast cells & basophils Chemotaxis of WBC

40. Cellular and humoral immunity differences Cellular • Is by T lymphocyte • Cells are processed in thymus • Exposure to antigen produces helper, suppressor, memory and cytotoxic cells • Lymphocytes burr holes in the cells to be destroyed by releasing substances like interlukin, prostaglandin etc. Humoral • Is by B lymphocyte • Cells are processed in liver and spleen • Exposure to antigen produces plasma and memory cells • Plasma cells synthesize and release free antibodies in to circulation

41. Cellular and humoral immunity differences Cellular • 80% of circulating lymphocytes belong to this group • Have role in responses against bacteria, fungi, viruses and also against transplanted organs and tissues. Humoral • Only 20% circulating lymphocytes belong to this group. • Have role against bacteria only

42. Immunization • Has been used for many years to produce acquired immunity against specific diseases • Injecting dead organisms that are no longer capable of causing diseases but still have their chemical antigen------- Typhoid, whooping cough, other types of bacterial diseases • Toxin treated with chemicals ---- not toxic in nature---- have antigens----- Tetanus , botulism, other toxic diseases • Organisms can be attenuted----- still carry specific antigen-----small pox, measles, ,many viral diseases

43. Passive Immunity • Temporary immunity can be achieved in a person without injecting antigen • By infusing antibodies , activated T- cells or both----- from other person or animal that has been immunized against the antigen • Antibodies---- 2-3 weeks • T-cells----- Few weeks

44. Immune deficiency diseases— • Due to defective component of immune system • Types— • 1.Congenital immune deficiency disease • eg-Di George’s syndrome • 2.Acquired immune deficiency disease (AIDS)

45. Boost self immunity THANK YOU