Immunology/ Pharmact Students Cells and Organs of the Immune System Lecture 2

1. Immunology/ Pharmact Students • Cells and Organs of the Immune System • Lecture 2 Dr. Mohammad Odibate Department of Microbiology and immunology Faculty of Medicine, Mu’tah University

2. Objectives The structure and functions of the of the primary and secondary lymphoid organs Types of white blood cell (WBC) population The principal functions of WBCs Structural features of WBCs

3. Principle of immune response MHC Macrophage T cell Activation of other types of lymphocytes B-lymphocyte

4. Lymphoid organs Secondary Lymphoid organs Primary Lymphoid organs Adenoids Tonsils Thymus Lymph nodes • Thymus & bone marrow are called central lymphoid organs • They are responsible for synthesis and maturation of lymphoid cells Spleen Peyer’s patches Mesenteric Lymph nodes Bone marrow

5. Primary lymphoid organs Bone marrow • The site of hematopoiesis • Hematopoiesis is the formation of blood cells. T lymphocytes B lymphocytes

6. Secondary lymphoid organs B cells leave bone marrow completely mature and start homing in the secondary lymphoid tissues , while T-cells complete their maturation in the thymus gland before settling in the secondary lymphoid tissues Mature B-cells • From blood circulation • To the Secondary • lymphoid organs Pre T-cells Thymus (for maturation) Peyer’s patches Lymph nodes Adenoids Spleen Mesenteric Lymph nodes Tonsils • Immune response takes place in the Secondary • lymphoid organs

7. Primary lymphoid organs Bone marrow • The site of hematopoiesis • Hematopoiesis is the formation of blood cellular components

8. Primary lymphoid organs Thymus • Location: in the anterior mediastinum just above the heart • Structure: containing lobules divided into • an outer cortex (C) and an • inner medulla (M) • Function: maturation of T cells from • which they are transported • to the secondary lymphoid • organs M C M C M C

9. Primary lymphoid organs Thymus Thymus reaches its greatest size just prior to birth, then atrophies with age and the production of new T-cells in the adult thymus drops away.

10. Primary lymphoid organs (Thymus) DiGeorge Syndrome Some of these genes are associated with thymus gland development This region contains about 45 genes 22q11.2 Norma region Chromosome 22 congenital absence of the thymus (aplasia, complete deletion) This will lead to immune disorders due to reduced T cell numbers Incomplete development of the thymus (hypoplasia, incomplete deletion) 22q11.2 Partial or complete deletion

11. Secondary lymphoid organs Lymph • Trap recognize • foreign antigen Lymph • The main sites of immune response and antibodies production through lymphatic vessels Secondary lymphoid organs

12. Secondary lymphoid organs Pathogen Ag complexed with MHC Lymph node APC

13. Secondary lymphoid organs Lymph nodes Lymph nodes act a sieve

14. Secondary lymphoid organs Lymph nodes Location: in the neck, axillae, groin, mediastinum and abdominal cavity • Function: filters antigens from the interstitial tissue

15. Secondary lymphoid organs Lymph nodes • Structure: T B

16. Dendritic cell Dendritic cell B B B B B B B T activation activation Migrate to the center of the primary follicle To differentiate into plasma cell. The follicle now is called Secondary follicle

17. Secondary lymphoid organs Lymph nodes • Structure:

18. Secondary lymphoid organs Spleen • Location: left upper quadrant of the abdomen • and weighing about 150 grams • Function: the largest single lymphoid organ in the • body, therefore, it is the major organ in which • antibodies are synthesized and released into • circulation.

19. Secondary lymphoid organs Spleen • Structure:

20. Secondary lymphoid organs Spleen • Structure:

21. Secondary lymphoid organs • Secondary lymphoid organs Spleen • Structure:

22. Secondary lymphoid organs Mucosa associated lymphoid tissue (MALT) • Location: found associated with the mucosal system gut-associated lymphoid tissues (GALT) bronchus-associated lymphoid tissue (BALT) lymphoid tissue lining the genitourinary tract ileum, Peyer's patches Esophagus MALT

23. Secondary lymphoid organs Mucosa associated lymphoid tissue (MALT) • Function: The major function of these organs is to provide local immunity by sIgA • and IgE production • Mode of activation: Antigens

24. Secondary lymphoid organs Mucosa associated lymphoid tissue (MALT)

25. Cells of the Immune System

26. Cells of the Immune System Neutrophils Containing different types of proteolytic enzymes such as lysozyme, collagenase and elastase The nucleus has 3-5 connected lobes Have short life span (6-7 hours in blood and few days in tissue spaces and do not multiply) They are called neutrophils because their granules stain poorly with the dyes used in staining leukocytes Neutrophils reach the site on infection at first Why?

27. Cells of the Immune System Neutrophils Most abundant Inflammation site Highly motile Neutrophils chemoattractants are produced at first neutrophil monocyte monocyte neutrophil neutrophil neutrophil Neutrophils reach the site on infection at first Why?

28. Cells of the Immune System Monocytes Inflammation site neutrophil monocyte monocyte neutrophil neutrophil neutrophil

29. Cells of the Immune System Monocytes Half-life of 3 days in circulation Rounded or kidney shaped nuclei (12-15 μm) Monocytes in tissues called macrophages

30. Cells of the Immune System Macrophage Inflammation site Macrophage Macrophage monocyte monocyte

31. Cells of the Immune System Macrophage Histiocytes (in tissue) Kupffer cells (in liver) Macrophages survive for months and can multiply Alveolar macrophages (in lungs) Has different names in tissues Macrophage Microglial cells (in brain) • Functions • killing of microbes, infected cells, tumor cells • secretion of immunomodulatory cytokines • antigen processing and presentation to T cells Mesangial cells (in kidneys) Osteoclasts (in bone)

32. Cells of the Immune System Dendritic cells They are morphologically identified by spiny membranous projection on their surfaces. Their main function is to capture and transport protein antigen to the draining lymph node acting as antigen presenting cells (APC).

33. Thank you