Downloaded 156 times
Cells & organs of immune system
The document discusses the components and functions of the human immune system, detailing different types of immune cells such as lymphocytes, macrophages, and granulocytes, as well as primary and secondary lymphoid organs like bone marrow, thymus, lymph nodes, and spleen. It explains the development and differentiation of these cells, their roles in immunity, and the processes of hematopoiesis and antigen presentation. Additionally, it highlights the structural organization of lymphoid tissues and their significance in immune response.
More Related Content
Similar to Cells & organs of immune system
More from Dr. Harisingh Gour Vishwavidyalaya (A Central Universuty), Sagar, MP
Cells & organs of immune system
- 1. 1 Presented by: PRADDUMKUMAR NAMDEV BSc (hons) ZOOLOGY Enrollment NO. 17140007 IGNTU Amarkantak MP
- 2. Cells ofimmune system ◦ 1 Lymphocytes T-lymphocytes B-Lymphocytes NK cells ◦ 2. Phagocytic cells Monocytes Macrophages ◦ 3. granulocytes Neutrophils Basophils Eosinophils Mast cells ◦ 4. Dendriatic cells Organs of immune system ◦ A. primary lymphoid organs Bone marrow Thymus ◦ B. secondary lymhoid organs: Lymph nodes Spleen MALT 2
- 3. WBCs arethe principle cells of immune system formed hematopoietic stem cell by the process of hematopoiesis. Hematopoiesis occurs in yolk sac during 1st week of gestation. After 3rd month of gestation, hematopoiesis occurs in liver and spleen of fetus and after birth, it occurs in bone marrow. 3
- 4. 1. Lymphocytes T-lymphocytes B- lymphocytes NK cell 2. Phagocytic cells Monocytes Macrophages 3. Granulocytic cells Neutrophils Basophils Eosinophils Mast cells 4. Dendritic cells 4
- 5.
- 6.
- 7. Lymphocytes aresmall, round cells found in peripheral blood, lymph, lymph nodes, lymphoid organs and in tissues. Lymphocytes represent 20-45% of total cells in peripheral blood and 99% of total cells in lymph and lymph node. According to side lymphocytes are divided into small (5-8µm), medium (8-12µm) and large (12-15µm). Depending on life span lymphocytes are classified into short lived (2 weeks) and long lived (3 years or more or even lifelong). Broadly lymphocytes are divided into three sub-populations, on the basis of function and cell membrane components. ◦ T-lymphocytes ◦ B-lymphocytes ◦ Natural killer cell 7
- 8. Monocytes andmacrophages are mononuclear phagocytic cells. Granulocyte-monocyte progenitor cell differentiates into promonocytes and neutrophil. Promonocytes leaves the bone marrow and enter into blood stream where they differentiate into mature monocytes. Monocytes circulates in blood for about 8 hours, during which they enlarges and then enter into tissues and differentiates into specific macrophages and dendritic cells. 8
- 9. Blood monocytesmeasure 12-15 µm with a single lobed kidney shaped nucleus. It accounts for (2-8%) of blood leucocytes. Immunological Functions of monocytes: Helps in antigen processing and presentation Releases cytokines Specialized function in tissues Cytotoxicity 9
- 10. Monocyte migratesto tissue and differentiates into macrophages. Differentiation of monocytes into macrophages involves following changes: Cell enlarges 5-10 folds Intracellular granules increases in number and complexity Increase phagocytic ability Produces higher level of hydrolytic enzymes and cytokines Macrophages serve different functions in different tissues. ◦ Alveolar macrophages : in lungs ◦ Histiocyte: connective tissue ◦ Kuffer cell: liver ◦ Messangial cell: kidney ◦ Microglial cell: brain ◦ Osteoclast: bone 10
- 11. Immunological functions ofmacrophages: Phagocytosis Antigen presentation to T-cell Secretion of lymphokines IL-1, IL-6. IL-12. TNF-α etc. to activates inflammatory response Secretion of granulocyte monocyte colony (GMC) stimulating factors. 11
- 12. 1. NEUTROPHIL: A. Neutrophilsare (11-14µm) in diameter with multilobed nucleus with granules in cytoplasm. B. It constitutes 50-70 % of total circulating WBC and remains for 7-8 hours in blood and then migrates to tissues C. Life span is 3-4 days. D. Also known as polymorph nuclear (PMN) leucocyte. E. Neutrophils is stained by both acidic and basic dye. 12
- 13. Phagocytic rolein acute inflammatory response. It is the first immune cell to responds in inflammation. 13
- 14. Eosinophil's are(11-15µm) in diameter, heavily granulated with bilobed nucleus It is stained by acidic dye i.e. Eosin They are phagocytic and motile (migrate from cell into tissue space). Comprise 2-5% of WBCs. Imp. Role in defense against protozoan and helminth parasite by releasing cationic peptides & reactive oxygen intermediates into extracellular fluids. 14
- 15. Granules containvarious hydrolytic enzymes that kill parasites which are too large to be phagocytosed by neutrophils. Provide allergic inflammation. 15
- 16. Basophils arenon-phagocytic cell found in small number in blood and tissue Cytoplasm contains large number of prominent basophilic granules containing histamine, heparin, serotonin, and other hydrolytic enzymes Stained by basic dyes Immunological functions: Provide anaphylactic and atopic allergic reaction 16
- 17. Precursures areformed in bone marrow and released into the blood in an undifferentiated state, until they rach the tissues. They have ;large numbers of cytoplasmic granules containing histamine. Mast cells and basophils play role in allergic reactions. 17
- 18. Dendritic cellshave long cytoplasmic externsions that resembles to dendrites of nerve cell. They have highly pleomorphic with a small central body and many long needle like processes. Dendritic cells are antigen presenting cell (APC) because they possess MHC class. Immunological functions: Involved in antigen presentation to T-cells during primary immune response. Very little role in phagocytosis. 18
- 19.
- 20. Two main typesof organs present in immune system of humans: 1. Primary Lymphoid Organs 1. Bone marrow 2. Bursa of fabricius (in birds) 3. Thymus 2. Secondary Lymphoid Organs. 1. Lymph nodes 2. Spleen 3. Mucosa associated lymphoid tissue (MALT) 20
- 21.
- 22. Primary lymphoidorgans (PLO) are the major sites of lymphocyte development i.e. lympho- poiesis. Lymphocytes differentiate from lymphoid stem cells, proliferate and mature into functional cells called immuno-competent cells. In mammals, B-cell maturation occurs in the bone marrow and T-cell maturation occurs in the thymus. 22
- 23. A. location: Itis found in the cavities of most bones in the body including the skull, ribs, sternum, femur and spine. In birds, no bone marrow is found to be present, instead a lymphoid organ named Bursa identified by Fabricius called Bursa of Fabricius, is present and performs the same duty of bone marrow of mammals. 23
- 24. 2. Structure Bonemarrow of different bones mainly consists of a sponge like reticular framework located between long trabeculae. The spaces in this framework are filled with fat cells, stromal fibroblasts and precursors of blood cells 24
- 25.
- 26. 3. Functions: Thebone marrow is the main site of generation of all types of circulating blood cells in adult and is the principal site of B- cell maturation and proliferation. During foetal development, the generation of all blood cells, called haematopoiesis, occurs initially in blood island of yolk sac and para-aortic mesenchyme and later in the liver and spleen. Gradually, these functions are shifted to bone marrow. All blood cells originate from haematopoietic stem cell and become committed to differentiate along particular lineages (erythroid, megakaryocyte granulocytic, monocyte and lymphocytic). 26
- 27. Bone marrowis not only the source of all blood cells but also provides the microenvironment for the antigen independent differentiation of B-cell. Besides this, bone marrow serves as a secondary lymphoid organ where mature, virgin, antigen reactive lymphocytes (T & B cell) may respond to antigen, trapped by antigen presenting cells, such as macrophages. Thus, like spleen, bone marrow may provide an antigen processing environment. 27
- 28. I. location Thymusis located in the thoracic cavity (in the mediastinum), just above the heart and beneath the breast bone. Location of the Thymus in the Chest of Child. II. Origin: In mammals thymus develops from the endoderm of the third and fourth pharyngeal pouch. 28
- 29. III. Structure Thethymus is flat, bilobed, greyish lympho-epithelial organ. Each lobe is made of lobules separated from each other by strands of connective-tissue trabeculae and covered by a capsule. Each lobule consists of two compartments the outer com- partment (cortex) is densely packed with immature T-cells (thymocytes) And, the inner compartment (medulla) is sparsely populated with mature thymocytes which express CD44 (not found in the cortical thymocytes). 29
- 30.
- 31. There arebasically four types of cells found in thymus— ◦ Thymocytes ◦ dendritic cells ◦ epithelial cells ◦ Macrophages Both the cortex and medulla of the thymus are criss- crossed by a three dimensional stromal-cell network. 31
- 32. Out offour cell types, dendritic cells, epithelial cells and macrophages act in a combine manner, as a framework to assist in thymocyte maturation. Some thymic epithelial cells in the outer cortex, called nurse cells, have long membrane processes which surround as many as 50 thymocytes forming large multicellular complexes. Other cortical epithelial cells have long inter-connecting cytoplasmic processes that form a network. The thymocytes are differentiated and matured into different types of T-cells under hormonal influence. Lymphoid progenitor cells formed in the bone marrow migrate to the thymus under the influence of specialized thymic environment. 32
- 33. Besides theprimary lymphoid organs, there are some other lymphoid organs which are referred to as secondary lymphoid organs. Lymph nodes and spleen are the most important and highly organized secondary lymphoid organs. Besides these, less organized lymphoid tissue collectively called mucosal-associated lymphoid tissue (MALT) which includes Peyer’s patches in the small intestine, the tonsils, the appendix, as well as numerous lymphoid follicles within the lamina propria of the intestines and in the mucous membranes lining the upper airways, bronchi and genital tract. 33
- 34.
- 35. In caseof closed blood vascular system, blood remain always confined within the blood vessels. Lymph and lymphatic system bathe the tissue, tissue fluid and cells. As because lymphatic system represents an accessory route through which fluids or lymph can flow from interstitial spaces into the blood, which is comprised by tiny lymphatic vessels. There are different organized lymphoid tissues which are located all along the lymphatic vessels, remain as diffuse collections of lymphocytes and the macrophages and some other are organized into structures called as the lymphoid follicles. 35
- 36. These tworemain as aggregates of various cells surrounded by a network of draining lymphatic capillaries. These are designated as secondary lymphoid tissues. The secondary lymphoid organs are rich in macrophages and dendritic cells that trap and process antigens in T & B lymphocytes, which mediate the immune responses. The anatomical structure of these organs is designed to facilitate antigen trapping and its maximize opportunities for processed antigen are to be presented to antigen-sensitive cells. 36
- 37. 1. Location: Lymphnodes are located at major junctions of the network of lymph flow through lymphatic channels (lymphatic vessels. 2. structure: The lymph nodes of man are round or bean shaped structures placed on lymphatic vessels so that they can filter out any foreign material carried in the lymph. Lymph nodes consist of a fibrous reticular network filled with lymphocytes, macrophages and dendritic cells. Lymphatic sinuses penetrate the node. A sub-capsular sinus is located immediately under the connective tissue capsule of the node; other sinuses pass through the node but are most prominent in a medulla. Afferent lymphatic vessels (those flowing into the node) enter the lymphatics node around its circumference, and efferent lymphatic vessels (those flowing out of the node) leave from depression (or hilus) on one side. The blood vessels supplying a lymph node also enter and leave via hilus. 37
- 38.
- 39.
- 40.
- 41. The interiorof a lymph node is divided into three concentric zones—an outer cortex, a para-cortex and a central medulla. Each of which provides a distinct micro- environment. The cells in the cortex are predominantly (B-cells) lymphocytes (arranged in nodules), macrophages and follicular dendritic cells arranged in primary follicles. In lymph nodes, these follicles are stimulated by antigen, turned into secondary follicles to expand upto germinal centers where B-cells undergo somatic mutation. 41
- 42. Intense B-cellactivation and differentiation into plasma and memory B-cells. It occur in the germinal centers of lymph nodes. Cells that increase their ability to respond to an antigen leave the germinal center to colonize other secondary lymphoid organs. Cells with reduced ability undergo apoptosis (programmed cell death) and are removed by macrophages. The para-cortex sometime is referred to as thymus dependant area, in contrast to the cortex, which is thymus independent area. The para-cortex is largely constituted with T-lymphocytes and dendritic cells. The inter-digitating dendritic cells act as antigen presenting cells (APCS) and thus express class II MHC (Major Histocompatibility Complex) molecules. 42
- 43. The innermost layer of the lymph node is composed of lymphocytes, forming inter connecting strands in the medulla, called the medullary cord. Again these medullary cords surround the medullary sinuses which have plasma cells and some macrophages 43
- 44.
- 45. 1. Location Spleen,the secondary lymphoid organ is located high in the left abdominal cavity. The spleen is specially adapted for filtering blood and trapping blood-borne antigens and respond to systemic infections. 2. Structure Spleen is one of the most important lymphoid organ remain surrounded by a capsule. From the capsule, a no. of projections called trabeculae remain extended to the interior to form a compartmentalized structure. 45
- 46. There aretwo types of compartments, named red pulp and white pulp. These two pulps are separated by a diffused marginal zone: I. Red pulp: The red pulp of spleen consists of a network of sinusoids. Sinusoids are with huge macrophages and erythrocytes. Function: This splenic zone helps to destroy and remove old and defective red blood cells. Some of the macrophages within the red pulp contain engulfed red blood cells or iron pigments from degraded hemoglobin. 46
- 47. II. White pulp This zone is with T-lymphocytes. It surrounds the per arteriolar lymphoid sheath (PALS). Function: The T-cell-rich-PALS mediate the initial activation of B and T cells. Here, dendritic cells capture antigen and present it with T Helper (TH) cells. In terms these activated T-cells activate B cells. Activated B and TH cells together migrate to primary follicles present in the marginal zone. Primary follicles gradually develop characteristic secondary follicles after antigenic challenge and rapidly give rise to B-cells and plasma cells. 47
- 48.
- 49. Besides lymphnodes, spleen, mucosal associated lymphoid tissue (MALT) is also considered as secondary lymphoid organ. I. Location: The majority of secondary lymphoid tissue in human body is located within the lining of digestive, respiratory and genitourinary tracts. These are collectively called Mucosal Associated Lymphoid Tissue (MALT) There are several types of MALT. Two major MALT includes Bronchial Associated Lymphoid Tissue (BALT) and Gut Associated Lymphoid Tissue (GALT) GALT includes the tonsils, adenoids, and specialised regions in the small intestine called Peyer’s patches. II. Structure: Loose cluster of lymphoid cells are present with little organizations in the lamina propria of intestinal villi to organised structures such as the tonsils, appendix and Peyer’s patches. 49
- 50. MALTs aremeant for the production of huge antibody-producing plasma cells which are very essential for the body defense. 50
- 51. LIFE SCIENCES FUNDAMENTALSAND PRACTICES –I BY: PRANAV KUMAR AND USHA MINA PUBLICATION: PATHFINDER, NEW DELHI WWW.BIOLOGYDISCUSSION.COM WWW.ONLINEBIOLOGYNOTES.COM IMAGE SOURCES SLIDE SHARE GOOGLE IMAGES 51
- 52.