Human immune system

1. Human immune system CELLS COOPERATION IN IMMUNE RESPONSE

2. PRIMARY or central LYMPHOID ORGANS are responsible for synthesis and maturation of immunocompetant cells. These include the bone marrow and the thymus. PERIPHERAL or secondary LYMPHOID ORGANS are sites where the lymphocytes localise, recognise foreign antigen and mount response against it. These include the lymph nodes, spleen, tonsils, adenoids, appendix, and clumps of lymphoid tissue in the small intestine known as Peyer's patches. They trap and concentrate foreign substances, and they are the main sites of production of antibodies.

4. Cells of the Immune System White Blood Cells Phagocytes - Neutrophils Macrophages Lymphocytes

6. White blood cells

7. Lymphocyte (could be B cell or T cell!)

8. Lymphocytes • Present in lymphoid organs and in blood • Groups • T-lymphocytes (grow up in thymus) • B-lymphocytes (grow up in bone marrow) • Each one has receptors for a specific antigen • Recognize millions of different antigens! • Diversity generated by: • rearrangement of antigen receptor genes • different joining of the gene segments • Gene rearrangement studies

11. Lymphocytes B lymphocytes • Live in blood, bone marrow, lymphoid tissues • Basic function: make antibodies (immunoglobulins) • B-cell receptor complex recognizes antigens • binds antigen • sends signals to T cells • Antigens can be free and circulating (don’t have to be bound to MHCs or displayed by other cells to be recognized!)

12. The B-Cell Receptor

16. Lymphocytes T lymphocytes • Live in blood, bone marrow, lymphoid tissues • Two basic functions: • kill stuff • help other cells do their jobs • T-cell receptor (TCR) complex recognizes antigens • binds antigen • sends signals to the T cell • Antigens must be: • displayed by other cells… • …AND bound to an MHC receptor

18. T Cell Selection in the Thymus Chapter 21, Immune System Figure 21.7

20. The T-Cell Receptor

21. The T-Cell Receptor Antigen-presenting cell T cell

26. Lymphocytes T lymphocytes • Helper T cells • CD4+ (and CD8-) • help B cells make antibodies • help macrophages eat bugs • decreased in patients with AIDS • Cytotoxic T cells • CD8+ (and CD4-) • kill virus-infected cells and tumor cells

27. CD8+ T cells surrounding tumor cell

28. Lymphocytes Natural Killer Cells • Belong to innate immunity arm • No highly variable receptors like T and B cells • Main job: recognize and kill damaged or infected cells • Antigens don’t have to be bound to MHCs or displayed by other cells!

29. Natural killer cell

30. Natural killer cell (top) killing infected cell (bottom)

31. Antigen-presenting cells • Main job: catch antigens and display them to lymphocytes • Dendritic cells • Have fine cytoplasmic projections • Present all over body: skin, lymph nodes, organs • Capture bug antigens, display to B and T cells • Other APCs • Macrophages eat bugs and present antigens to T cells, which tell macrophages to kill bugs • B cells present antigens to helper T cells, which tell B cells to make antibodies

33. dendritic cells

35. Antigen-presenting cells (APC) activate T helper cells

36. APC presents peptide to Т helper

37. T helper 2 activates B lymphocyte

39. Humoral immune response

42. Cell-mediated immune response

44. Взаємодія клітин в імунній відповіді