The document discusses the organs of the immune system. It describes primary lymphoid organs like the thymus, where T cells mature, and bursa of Fabricius, where B cells mature in birds. Secondary lymphoid organs include lymph nodes and Peyer's patches in the intestines, which contain follicles where B and T cells interact with antigens and activate an immune response. Lymphocytes then circulate through the blood and lymph, migrating between secondary lymphoid organs to survey for pathogens and launch adaptive immune responses.

1. THE ORGANS OF THE IMMUNE SYSTEM

3. Lymphocytes

5. Lymphocytes

6. SOURCE OF LYMPHOCYTES Fetus Primary Lymphoid Organs Secondary Lymphoid Organs Adult

7. SOURCE OF LYMPHOCYTES

9. SOURCE OF LYMPHOCYTES

10. HUMAN THYMUS

11. PRIMARY LYMPHOID ORGANS THYMUS (T cell maturation) (> lymphocytes) (< lymphocytes)

12. The functional thymus consists of two cell populations; the stromal cells and the thymocytes. The stromal cells include (1) the subcapsular epithelial cells; (2) the cortical epithelial cells; (3) the medullary epithelial cells; (4) macrophages; and (5) dendritic cells of bone marrow origin. (From Kierszenbaum AL: Histology and cell biology: an introduction to pathology, St Louis, 2002, Mosby.)

13. MHC-dependiente

14. Effects of Adult Thymectomy on Immune Response

15. CHICKEN THYMUS AND BURSA OF FABRICIUS

17. BURSA OF FABRICIUS (B cell maturation) follicle lumen Cortex (lymphocytes, M Ø, plasma cells) medulla

18. PEYER’S PATCHES Group I (90% Ileum ) Ruminants, Pigs, Horses, Dogs, Humans. Group II Illeum/Jejunum) Rabbits, Rodents.

19. When stimulated by antigen, immunoglobulin A (IgA)-producing B cells are produced in inductive sites, such as the Peyer’s patches.

20. The role of M cells as antigen-processing cells in the intestinal wall. Antigen that enters enterocytes is usually rapidly degraded in lysosomes. Antigen that enters M cells is not degraded. It may be presented directly to intraepithelial lymphocytes within the M. Yersinia, M. tuberculosis, Listeria, reovirus , Salmonella.

21. Structure of the two different types of Peyer’s patch (PP) in sheep. A, An ileal PP at age 8 weeks. B, A PP from the jejunum, also at 8 weeks. Original magnification ×32. (From Reynolds JD, Morris B: Eur J Immunol 13:631, 1983.)

22. SECONDARY LYMPHOID ORGANS LYMPH NODE

23. SECONDARY LYMPHOID ORGANS LYMPH NODE

24. (B cells) (stimulated) (T cells) (unstimulated) (B cells, macrophages, plasma cells) SECONDARY LYMPHOID ORGANS LYMPH NODE

25. SECONDARY LYMPHOID ORGANS LYMPH NODE secondary follicle primary follicle medulla subcapsular sinus dendritic cells

26. Circulation of Lymphocytes

28. HIGH ENDOTHELIAL VENULES

30. HIGH ENDOTHELIAL VENULES

32. HIGH ENDOTHELIAL VENULES

35. RP WP B cell follicle PLS Marginal Zone SPLEEN

37. SPLEEN

38. PERIARTERIOLAR LYMPHOID SHEATS (PALS) B cells T cells arteriole