Cells and organs of Immune systems
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This presentation slide is about the different cell types and organs that involve in our immune system
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Cells and organs of Immune systems
- 1. Cells and Organs of the Immune Systems Dr Rohimah Mohamud Department of Immunology, USM 21 Nov 2018
- 2. Immune system consists of a complex network of cells and organs that work together to protect our body from infections/diseases
- 3. Lecture objectives • Structure and organization of the immune system. • Functions of primary and secondary lymphoid organs. • Lymphopoiesis and lymphocytes subsets • Accessory cells of the immune system and their functions.
- 4. Structure and organization of the immune system • Primary lymphoid organs ▫ Fetal liver ▫ Adult bone marrow ▫ Thymus • Secondary lymphoid organs and tissues ▫ Lymph nodes (LN) ▫ Spleen • Mucosal-associated lymphoid tissues ▫ Tonsils and adenoids ▫ Nose-, bronchus-associated lymphoid tissues ▫ Peyers patches ▫ Cryptopaches and isolated lymphoid follicles
- 5. • Bone marrow = hematopoietic stem cells (HSCs, hematopoiesis) differentiate into all sorts of blood • Thymus is responsible for directing the maturation of immature thymocytes into T cells and lymphatic cells • Spleen = filters the blood, destroying old or damaged blood vessels and prime naive T cells • LN = filter lymph. Lymph is composed of fluids which drain from tissues. It is collected at various locations throughout the body and circulates through a series of lymph nodes Organs of the immune system http://www.niaid.nih.gov/topics/immunesystem/Pages/structure.aspx
- 6. Structure and organization of the bone marrow • Soft, flexible connective tissue within bone cavities • Red marrow- produce blood cells • Yellow marrow- fatty tissues formation • The only bones to carry red bone marrow throughout life, are the vertebrae (back bones), sternum (breast bone), hip bone and skull bones http://simple.wikipedia.org/wiki/Bone_marrowhttp://mstinsonbc.wikispaces.com/Skeletal+-+Function
- 7. Structure and organization of the thymus http://medcell.med.yale.edu/systems_cell_biology_old/lymphatics/aged_thymus.php It is fully developed at birth and grows until puberty, after which it becomes fatty and shrinks to about 15 % of its maximum size.
- 8. Structure and organization of the spleen • filters the blood, destroying old or damaged blood vessels and prime naive T cells •White pulp (lymphoid tissues) = immune surveillance and initiation of humoral and cell-mediated immunity • Red pulp (venous sinuses and cellular cords) = removes damaged cells and acts as a site for iron storage and turnover
- 9. Structure and organization of the LN • LN are yellowish, bean-shaped structures dispersed along lymphatic vessels • Cortex: B cells and follicular dendritic cells (DC): germinal center • Paracortex region: T cells and DC • Subcapsular sinus and medullary cord: Macrophages
- 10. Lecture objectives • Structure and organization of the immune system. • Functions of primary and secondary lymphoid organs. • Lymphopoiesis and lymphocytes subsets • Accessory cells of the immune system and their functions.
- 11. Functions of primary lymphoid organs • Bone marrow = source of self-renewing stem cells; giving rise to T and B cell-precursors and serving as a repository for plasma cells; bone marrow stromal cells secrete growth factors for hemopoietic stem cell dev • Thymus = T cells maturation; central tolerance (positive and negative selections)
- 12. Functions of secondary lymphoid organs • LN = discriminate between dangerous foreign antigens and self-antigens; peripheral tolerance • Spleen = crucial site for antigen clearance and presentation to T and B cells; filters blood and removes damaged platelets, aged erythrocytes and apoptotic cells
- 13. Lecture objectives • Structure and organization of the immune system. • Functions of primary and secondary lymphoid organs. • Lymphopoiesis and lymphocytes subsets • Accessory cells of the immune system and their functions.
- 14. Lymphopoiesis: the development of lymphocytes http://atlasgeneticsoncology.org/Genes/GC_MEIS1.html HSCP or pHSC: Hematopoietic Stem Cell Proliferative/ pluripotential HSC: Hematopoietic Stem Cell LPC: Lymphoid Precursor Cell MPC: Myeloid Precursor Cell Note these are adult stem cells, NOT embryonic stem cells. Self-renewing stem cells.
- 15. Stages of T and B lymphocytes development Cellular and Molecular Immunology 7th Edition
- 16. Subsets of lymphocytes with regard to surface markers and functions • Cell surface markers are proteins expressed on the surface of cells that often conveniently serve as markers of specific cell types • Commonly used as cell markers in immunophenotyping via flow cytometry • CD => Cluster Of Differentiation • Over 300 CD Markers • T cells => CD4 or CD8 and CD3 • B cells => CD19 • NK cells => CD56 • Monocytes/Macrophages => CD14 • Dendritic Cells => CD1c (Human), CD11c (mouse)
- 17. Subsets of lymphocytes with regard to surface markers and functions Cellular and Molecular Immunology 7th Edition
- 18. T lymphocytes • Adaptive immune response • help, suppress or regulate immune responses by releasing T cell cytokines • Important: ▫ B cell antibody class switching ▫ the activation and growth of cytotoxic T cells ▫ maximizing bactericidal activity of phagocytic cells • CD3+CD4+
- 19. Lecture objectives • Structure and organization of the immune system. • Functions of primary and secondary lymphoid organs. • Lymphopoiesis and lymphocytes subsets • Accessory cells of the immune system and their functions.
- 20. • T and B cells: ▫ Subset based on CD markers ▫ Subset based on History of Antigen Exposure (naïve, activated/effector and memory lymphocytes) • Accessory cells: ▫ Phagocytes: neutrophils, mononuclear phagocytes ▫ Mast cells, basophils, eosinophils ▫ Antigen presenting cells (APC): dendritic cells (DC), APC-for effector T cells, follicular DC Cells of the immune system
- 21. Accessory cells of the immune system • there are other cells that participate in the immune response besides the B and T lymphocytes=> accessory cells • play a central role in antigen presentation (e.g. dendritic cells) and elimination (e.g. mononuclear phagocytes) • derived from the myeloid line, act both in the natural or innate immune response and in the adaptive immune response
- 22. Maturation of mononuclear phagocytes and dendritic cells Cellular and Molecular Immunology 7th Edition
- 23. Functions in innate immune response • Phagocytosis of foreign particles (microbes and antigens and even self-cells when injured or dying) • Secretion of enzymes and oxidative metabolites (respiratory burst- oxygen radicals, NO, prostaglandins) • Cytokine production which recruit other inflammatory cells, as well as growth factors for fibroblasts and vascular endothelial cells • Antigen presentation – processing and re- expression of MHCII + foreign Ag epitope • Opsonization- Fc receptor for IgG
- 24. Dendritic Cells • Professional antigen presenting cells • All DC express the Major Histocompatibility Complex class II (MHCII) • Myeloid and palsmacytoid DC characterized on surface markers Other subsets: migratory property from tissue sites e.g. Langerhans DC from epithelial and Interstitial DC from tissue
- 25. Follicular DC • found intermingled in specialized collections of activated B cells (called germinal centers), in the lymphoid follicles of the lymph nodes, spleen, and mucosal lymphoid tissues • Do not express MHC II molecules = unrelated to the DC that present antigens to T cells • Express FcR for antibodies/complement
- 26. Follicular DC Antigen is delivered to B cells through: • afferent lymphatics conduits • captured by macrophages and delivered to the follicle • DC in medulla Follicular DC trap antigens and display these antigens on their surfaces for recognition by B cells Cellular and Molecular Immunology 7th Edition
- 27. Accessory cells with regard to surface markers http://www.stembook.org/node/737
- 28. Recap: Lecture objectives • Structure and organization of the immune system. • Functions of primary and secondary lymphoid organs. • Lymphopoiesis. • Subsets of lymphocytes with regard to surface markers and functions. • Th1 and Th2 lymphocyte subsets. • Accessory cells of the immune system and their functions.
- 29. References
Editor's Notes
- Complex network of organs, cells and molecules To maintain homeostasis But, focus on cells and organs Why not on tissue of immune system
- While bone marrow isn't considered an organ, it is vital to the immune system It creates hematopoietic stem cells through the process of hematopoiesis. These stem cells differentiate into all sorts of blood and lymphatic cells - such as red blood cells, white blood cells, platelets, immature thymocytes, B cells, etc Bone marrow is a tissue that lies inside most of your bones. in response to hormones released by cells which make up the bone marrow. Some cells of the immune system mature in the bone marrow, and some travel to other areas of the body to complete their maturation. The thymus is a small, butterfly-shaped organ that lies between your breastplate and your heart. You probably haven't heard of it because, after adolescence, it doesn't do much. It is fully developed at birth and grows until puberty, after which it becomes fatty and shrinks to about 15% of its maximum size. During its most active time, the thymus is responsible for directing the maturation of immature thymocytes into T cells. T cells are the managers of the immune system, instructing other cells how to react to foreign substances. During this maturation in the thymus, T cells learn to differentiate between "self" (the body's own cells) and "nonself" (foreign objects, organisms, or diseased cells). If a T cell thinks a self cell is foreign, it is destroyed, as it could cause the effects of an autoimmune disease if allowed to leave the thymus. The spleen performs several functions; it filters the blood, destroying old or damaged blood vessels. It also contains many specialized cells (e.g. T cells) of the immune system that look for foreign particles as blood circulates. T cells also receive information from migratory dendritic cells and macrophages, which ingest foreign microorganisms and present their pieces to T cells. If a T cell recognizes a presented particle as foreign, it instructs a B cell (which also recognizes the particle) to create antibodies against it. Lymph nodes are a bit like the spleen, but instead of filtering blood, they filter lymph. Lymph is composed of fluids which drain from tissues. It is collected at various locations throughout the body and circulates through a series of lymph nodes, eventually returning to the blood for circulation. Unwelcome microorganisms enter the lymph nodes either by circulating with lymph or by ingestion by a cell that then travels to the lymph node. Lymph nodes contain the same specialized cells found in the spleen, which sample the incoming particles and respond accordingly. These important organs make up the framework of the immune system, providing meeting locations for specialized cells to communicate.
- The majority of our bone marrow is red marrow. As we grow and mature, increasing amounts of red marrow is replaced by fat cells to form yellow marrow. On average, bone marrow can generate hundreds of billions of new blood cells every day. The only bones to carry red bone marrow throughout life, are the vertebrae (back bones), sternum (breast bone), hip bone, and skull bones. Thus, any disease of bone marrow in adults is first seen in these bones ! meaning that it is richly supplied with a large number of blood vessels Produces blood cells, for fatty tissues formation one marrow is separated into a vascular section and non-vascular sections. The vascular section contains blood vessels that supply the bone with nutrients and transport blood stem cells and mature blood cells away from the bone and into circulation. The non-vascular sections of the bone marrow are wherehematopoiesis or blood cell formation occurs. This area contains immature blood cells, fat cells, white blood cells (macrophages and plasma cells), and thin, branching fibers of reticular connective tissue. While all blood cells are derived from bone marrow, some white blood cells mature in other organs such as the spleen , lymph nodes , and thymus gland.
- Bilobed organ on top of heart Cortex and medulla
- Lymphocytes develop from bone marrow stem cells and mature in the generative lymphoid organs (bone marrow and thymus for B and T cells, respectively) and then circulate through the blood to secondary lymphoid organs (lymph nodes, spleen, regional lymphoid tissues such as mucosa-associated lymphoid tissues). Fully mature T cells leave the thymus, but immature B cells leave the bone marrow and complete their maturation in secondary lymphoid organs. Naïve lymphocytes may respond to foreign antigens in these secondary lymphoid tissues or return by lymphatic drainage to the blood and recirculate through other secondary lymphoid organs.
- any of various cells of the immune system that interact with T cells in the initiation of the immune response
- Follicular dendritic cells (FDCs) are cells with membranous projections that are found intermingled in specialized collections of activated B cells, called germinal centers, in the lymphoid follicles of the lymph nodes, spleen, and mucosal lymphoid tissues. FDCs are not derived from precursors in the bone marrow and are unrelated to the dendritic cells that present antigens to T lymphocytes. FDCs trap antigens complexed to antibodies or complement products and display these antigens on their surfaces for recognition by B lymphocytes. This is important for the selection of activated B lymphocytes whose antigen receptors bind the displayed antigens with high affinity (see Chapter 11).
- a quick recap of the lecture’s obj that we’ve gone through