Anatomy and Biology of the Immune Response <ul><li>The bone marrow is the source of the precursor cells that ultimately gi...
Anatomy and Biology of the Immune Response <ul><li>The production of immune cells is one component of haemopoiesis </li></...
Anatomy and Biology of the Immune Response <ul><li>Both the microenvironment within the marrow and the influence of solubl...
Cells of the Immune System <ul><li>Granulocytes </li></ul><ul><li>The granulocyte/monocyte lineage gives rise to precursor...
Cells of the Immune System <ul><li>Granules with intense blue staining are found in basophils, which make up  </li></ul><u...
Cells of the Immune System <ul><li>Polymorphonuclear cell describes the multilobed nuclei of granulocytes; synonymous with...
Cells of the Immune System <ul><li>Granulocytes circulate in the blood and migrate into the tissues particularly during in...
Cells of the Immune System <ul><li>Monocytes and Dendritic Cells </li></ul><ul><li>Monocytes form between 5 and 10% of cir...
Cells of the Immune System <ul><li>Macrophages may also arise following division of immature forms of monocytes </li></ul>...
Cells of the Immune System <ul><li>Several specialized forms of the mature cell exist including alveolar macrophages in th...
Cells of the Immune System <ul><li>Dendritic cells are bone marrow derived and have a specialized function in the activati...
Cells of the Immune System <ul><li>Lymphocytes </li></ul><ul><li>Make up the final 25-35% of white cells and derive their ...
Cells of the Immune System <ul><li>Are found in the blood, lymphoid organs or tissues and also at sites of chronic inflamm...
Cells of the Immune System <ul><li>During fetal life, the liver is also an important site of B lymphocyte development </li...
Cells of the Immune System <ul><li>B lymphocytes may mature into plasma cells in which form they remain fixed in the tissu...
Cells of the Immune System <ul><li>The B lymphocyte obtained its name from early studies on antibody production in birds s...
Cells of the Immune System <ul><li>Removal of the thymus from adult mice appeared to have little effect on the animals or ...
Cells of the Immune System <ul><li>T lymphocyte involvement with the thymus takes place in early life and is critical to t...
Cells of the Immune System <ul><li>In the absence of T lymphocytes, protection against infection is fatally impaired  </li...
Cells of the Immune System <ul><li>T lymphocytes </li></ul><ul><ul><li>Two subsets </li></ul></ul><ul><ul><li>CD4 +  T cel...
Cells of the Immune System <ul><li>The total number of lymphocytes in a healthy adult is about 10 12 , of which 0.1% are r...
Cells of the Immune System <ul><li>Instead, lymphocytes have the distinctive feature of recirculation between the blood, t...
Cells of the Immune System <ul><li>Recirculation times vary from cell to cell, depending upon what is encountered during t...
Cells of the Immune System <ul><li>Rather than being random, recirculation is a highly regulated process of immune surveil...
Cells of the Immune System <ul><li>Natural killer (NK) cells </li></ul><ul><li>Is a functional definition: cells with this...
Cells of the Immune System <ul><li>A population of cells defined morphologically as large granular lymphocytes (LGL) also ...
Cells of the Immune System <ul><li>Unlike T lymphocytes, NK cells do not require the thymus for their maturation, though a...
Cells of the Immune System
Cells of the Immune System
Organs of the Immune System <ul><li>Organs of the lymphoid system are divided into:- </li></ul><ul><ul><li>primary and </l...
Organs of the Immune System <ul><li>Primary lymphoid organs in humans are the bone marrow and thymus, since they are the s...
Organs of the Immune System <ul><li>Secondary lymphoid organs (lymph nodes and spleen) are not essential for the generatio...
Organs of the Immune System <ul><li>Lymph nodes in particular anatomical sites are highly specialized, those surrounding t...
Organs of the Immune System <ul><li>The thymus develops from the third and fourth pharyngeal pouches in the 6 th  week of ...
Organs of the Immune System <ul><li>The thymus is at its largest, in proportion to body mass, at birth and thereafter show...
Organs of the Immune System <ul><li>Lymph nodes </li></ul><ul><li>Lymphocytes enter the lymph nodes either through the lym...
Organs of the Immune System <ul><li>Primary follicles are characteristic of a resting state and suggest no recent immune a...
Organs of the Immune System <ul><li>Secondary follicles arise following stimulation of a local immune response </li></ul><...
Organs of the Immune System <ul><li>The germinal centre is surrounded by a mantle of smaller, resting B lymphocytes </li><...
Organs of the Immune System <ul><li>The paracortical area of the node is predominantly composed of T lymphocytes as well a...
Organs of the Immune System <ul><li>The medulla has characteristic medullary cords of lymphoid cells which tend to become ...
Organs of the Immune System <ul><li>They do so via large cuboidal endothelial cells present on specialized structures call...
Organs of the Immune System <ul><li>Payer's patches are lymphoid aggregates with follicles, germinal centers and a surroun...
Organs of the Immune System <ul><li>Spleen </li></ul><ul><li>Has a white pulp comprising lymphoid tissue and a red pulp co...
Organs of the Immune System <ul><li>The red pulp is an important site for the removal of defective red and white blood cel...
Organs of the Immune System <ul><li>The importance of the spleen in protection against encapsulated organisms ( S pneumoni...
Characteristics of the Immune Response <ul><li>Specificity </li></ul><ul><li>The ability to discriminate among different m...
Characteristics of the Immune Response <ul><li>Adaptiveness </li></ul><ul><li>The ability to respond to previously unseen ...
Characteristics of the Immune Response <ul><li>Discrimination between self and nonself </li></ul><ul><li>The ability to re...
Characteristics of the Immune Response <ul><li>Memory </li></ul><ul><li>The ability to recall previous contact with a fore...
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Anatomy and biology of immune response

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Anatomy and biology of immune response

  1. 1. Anatomy and Biology of the Immune Response <ul><li>The bone marrow is the source of the precursor cells that ultimately give rise to the cellular constituents of the immune system, save for one period during fetal life when the liver is also a site of immune cell development </li></ul>
  2. 2. Anatomy and Biology of the Immune Response <ul><li>The production of immune cells is one component of haemopoiesis </li></ul><ul><ul><li>Process by which all cells that circulate in the blood arise and mature </li></ul></ul><ul><li>There is a single precursor cell that is capable of giving rise to all blood cell lineages ranging from platelets to lymphocytes  pluripotent haemopoietic stem cell </li></ul>
  3. 3. Anatomy and Biology of the Immune Response <ul><li>Both the microenvironment within the marrow and the influence of soluble mediators that act as colony stimulating factors are important determinants for the mechanism by which a pluripotent stem cell in the bone marrow matures into any one of the immune cells </li></ul>
  4. 4. Cells of the Immune System <ul><li>Granulocytes </li></ul><ul><li>The granulocyte/monocyte lineage gives rise to precursors that mature within the bone marrow and are released into the blood </li></ul><ul><li>Constitute ~65% of all white cells and derive their name from the large numbers of granules found in their cytoplasm </li></ul>
  5. 5. Cells of the Immune System <ul><li>Granules with intense blue staining are found in basophils, which make up </li></ul><ul><li>0.5-1% of granulocytes </li></ul><ul><li>Red-staining granules are present in eosinophils (3-5%) </li></ul><ul><li>Neutrophils (90-95%) have granules that remain relatively unstained </li></ul>
  6. 6. Cells of the Immune System <ul><li>Polymorphonuclear cell describes the multilobed nuclei of granulocytes; synonymous with neutrophils which constitute by far the majority of granulocytes but eosinophil nuclei may have a similar appearance </li></ul>
  7. 7. Cells of the Immune System <ul><li>Granulocytes circulate in the blood and migrate into the tissues particularly during inflammatory responses; exception is the mast cell which is fixed in the tissues </li></ul>
  8. 8. Cells of the Immune System <ul><li>Monocytes and Dendritic Cells </li></ul><ul><li>Monocytes form between 5 and 10% of circulating WBC, have a short half-life spending approx. 24 hrs in blood </li></ul><ul><li>Enter extravascular pool and become resident in the tissues where they are termed macrophages </li></ul>
  9. 9. Cells of the Immune System <ul><li>Macrophages may also arise following division of immature forms of monocytes </li></ul><ul><li>Monocyte and macrophage are larger than neutrophils and lymphocytes, have a single nucleus and abundant granular cytoplasm </li></ul>
  10. 10. Cells of the Immune System <ul><li>Several specialized forms of the mature cell exist including alveolar macrophages in the lung, Kupffer cells in the liver, mesangial cells in the kidney, microglial cells in the brain, osteoclasts in bone and other macrophages lining channels in the spleen and lymph nodes </li></ul>
  11. 11. Cells of the Immune System <ul><li>Dendritic cells are bone marrow derived and have a specialized function in the activation and priming of lymphocytes </li></ul><ul><li>Some specialized forms of these cells exist: for example, follicular dendritic cells in the lymph nodes </li></ul>
  12. 12. Cells of the Immune System <ul><li>Lymphocytes </li></ul><ul><li>Make up the final 25-35% of white cells and derive their name from a close association with the lymphatic system </li></ul><ul><li>Lymphocytes are divided into two subtypes </li></ul><ul><ul><li>B and T present in blood in a ratio of 1:5 </li></ul></ul>
  13. 13. Cells of the Immune System <ul><li>Are found in the blood, lymphoid organs or tissues and also at sites of chronic inflammation </li></ul><ul><li>B lymphocytes differentiate within the bone marrow before being released into the circulation </li></ul>
  14. 14. Cells of the Immune System <ul><li>During fetal life, the liver is also an important site of B lymphocyte development </li></ul><ul><li>The primary role of these cells is the recognition of macromolecules (termed antigens) through surface receptors (called antibodies) </li></ul>
  15. 15. Cells of the Immune System <ul><li>B lymphocytes may mature into plasma cells in which form they remain fixed in the tissues and function as secretors of antibody </li></ul>
  16. 16. Cells of the Immune System <ul><li>The B lymphocyte obtained its name from early studies on antibody production in birds showing that removal of a lymphoid organ known as the bursa of Fabricius from near the hindgut of a chick results in a complete inability to produce antibody </li></ul><ul><li>These antibody-producing cells then became known as bursa-derived, or B lymphocytes </li></ul>
  17. 17. Cells of the Immune System <ul><li>Removal of the thymus from adult mice appeared to have little effect on the animals or their lymphocytes, but thymectomy performed soon after birth had profound consequences reducing the numbers of lymphocytes in circulation and leaving the mice prone to death from infection </li></ul>
  18. 18. Cells of the Immune System <ul><li>T lymphocyte involvement with the thymus takes place in early life and is critical to their development </li></ul><ul><li>During this period, they acquire the ability to recognize and bring about the death of transplanted foreign tissues in a process termed graft rejection which implies an ability to distinguish self and non-self </li></ul>
  19. 19. Cells of the Immune System <ul><li>In the absence of T lymphocytes, protection against infection is fatally impaired </li></ul><ul><li>Though not capable of producing antibody themselves, T lymphocytes make a telling contribution to B lymphocyte function </li></ul>
  20. 20. Cells of the Immune System <ul><li>T lymphocytes </li></ul><ul><ul><li>Two subsets </li></ul></ul><ul><ul><li>CD4 + T cells or T helper cells (66%) </li></ul></ul><ul><ul><li>CD8 + T cells or T cytotoxic/suppressor cells (33%) </li></ul></ul>
  21. 21. Cells of the Immune System <ul><li>The total number of lymphocytes in a healthy adult is about 10 12 , of which 0.1% are renewed daily </li></ul><ul><li>Collectively they weigh almost half as much as the liver, yet they do not reside in any single organ </li></ul>
  22. 22. Cells of the Immune System <ul><li>Instead, lymphocytes have the distinctive feature of recirculation between the blood, tissues and lymphoid organs </li></ul>
  23. 23. Cells of the Immune System <ul><li>Recirculation times vary from cell to cell, depending upon what is encountered during the journey, but on average, a lymphocyte will complete a cycle in 1-2 days </li></ul>
  24. 24. Cells of the Immune System <ul><li>Rather than being random, recirculation is a highly regulated process of immune surveillance, controlled according to cell type and anatomy </li></ul><ul><li>B lymphocytes have a greater tendency to migrate to mucosal lymphoid tissue than do T lymphocytes </li></ul>
  25. 25. Cells of the Immune System <ul><li>Natural killer (NK) cells </li></ul><ul><li>Is a functional definition: cells with this activity are capable of lysing virus-infected cells and tumor cells </li></ul><ul><li>Like lymphocytes, NK cells are also identifiable by the presence of specialized surface glycoproteins </li></ul>
  26. 26. Cells of the Immune System <ul><li>A population of cells defined morphologically as large granular lymphocytes (LGL) also have natural killer function </li></ul><ul><li>This term is limited, however, since T lymphocytes actively involved in an immune response may appear large and granular </li></ul>
  27. 27. Cells of the Immune System <ul><li>Unlike T lymphocytes, NK cells do not require the thymus for their maturation, though a small population of thymus-derived cells with NK function has been identified </li></ul>
  28. 28. Cells of the Immune System
  29. 29. Cells of the Immune System
  30. 30. Organs of the Immune System <ul><li>Organs of the lymphoid system are divided into:- </li></ul><ul><ul><li>primary and </li></ul></ul><ul><ul><li>secondary organs </li></ul></ul>
  31. 31. Organs of the Immune System <ul><li>Primary lymphoid organs in humans are the bone marrow and thymus, since they are the sites of development and maturation of the lymphocytes </li></ul>
  32. 32. Organs of the Immune System <ul><li>Secondary lymphoid organs (lymph nodes and spleen) are not essential for the generation of lymphocytes but have a key role in the maturation of these cells and the development of immunity </li></ul>
  33. 33. Organs of the Immune System <ul><li>Lymph nodes in particular anatomical sites are highly specialized, those surrounding the upper and lower respiratory tracts being known as the mucosa-associated lymphoid tissue (MALT) and those in the gut, the gut-associated lymphoid tissue (GALT) </li></ul>
  34. 34. Organs of the Immune System <ul><li>The thymus develops from the third and fourth pharyngeal pouches in the 6 th week of fetal life </li></ul><ul><li>Immature cells enter the cortex and receive the close attention of a mixture of thymic epithelial and macrophage-derived cells, resulting in their development into immature T lymphocytes </li></ul>
  35. 35. Organs of the Immune System <ul><li>The thymus is at its largest, in proportion to body mass, at birth and thereafter shows a relative decline in size </li></ul>
  36. 36. Organs of the Immune System <ul><li>Lymph nodes </li></ul><ul><li>Lymphocytes enter the lymph nodes either through the lymphatics or from the blood </li></ul><ul><li>The cortex of the lymph node contains follicles which are organized aggregates of lymphoid cells </li></ul>
  37. 37. Organs of the Immune System <ul><li>Primary follicles are characteristic of a resting state and suggest no recent immune activity </li></ul><ul><li>Are composed of B lymphocytes, macrophages and specialized macrophages with long cytoplasmic processes known as follicular dendritic cells </li></ul>
  38. 38. Organs of the Immune System <ul><li>Secondary follicles arise following stimulation of a local immune response </li></ul><ul><li>The germinal centre of the follicle enlarges and B lymphocytes undergo proliferation and differentiation </li></ul>
  39. 39. Organs of the Immune System <ul><li>The germinal centre is surrounded by a mantle of smaller, resting B lymphocytes </li></ul>
  40. 40. Organs of the Immune System <ul><li>The paracortical area of the node is predominantly composed of T lymphocytes as well as the specialized interdigitating dendritic cells which are important accessory cells in T lymphocyte responses </li></ul>
  41. 41. Organs of the Immune System <ul><li>The medulla has characteristic medullary cords of lymphoid cells which tend to become populated with plasma cells during immune reactions </li></ul><ul><li>Lymphocytes may also enter lymph nodes via the blood </li></ul>
  42. 42. Organs of the Immune System <ul><li>They do so via large cuboidal endothelial cells present on specialized structures called high endothelial venules (HEV) </li></ul>
  43. 43. Organs of the Immune System <ul><li>Payer's patches are lymphoid aggregates with follicles, germinal centers and a surrounding T cell area but they differ from peripheral lymph nodes in lacking a capsule and afferent lymphatics </li></ul>
  44. 44. Organs of the Immune System <ul><li>Spleen </li></ul><ul><li>Has a white pulp comprising lymphoid tissue and a red pulp comprising reticular tissue and sinuses bathed in blood </li></ul><ul><li>Is a combination of lymphoid organ, filter bed and reclamation site </li></ul>
  45. 45. Organs of the Immune System <ul><li>The red pulp is an important site for the removal of defective red and white blood cells which are cannibalized by resident macrophages </li></ul><ul><li>Cross section of white pulp </li></ul><ul><ul><li>Marginal zone – macrophage-rich area </li></ul></ul><ul><ul><li>Follicle – B cell area </li></ul></ul><ul><ul><li>Periarterial lymphatic sheath – T cell area </li></ul></ul>
  46. 46. Organs of the Immune System <ul><li>The importance of the spleen in protection against encapsulated organisms ( S pneumoniae ) probably results from a combination of its ability to slow and filter circulating blood and its capacity to act as a rapid response unit in generating specific antimicrobial antibodies </li></ul>
  47. 47. Characteristics of the Immune Response <ul><li>Specificity </li></ul><ul><li>The ability to discriminate among different molecular entities presented to it and to respond only to those uniquely required, rather than making a random, undifferentiated response </li></ul>
  48. 48. Characteristics of the Immune Response <ul><li>Adaptiveness </li></ul><ul><li>The ability to respond to previously unseen molecules that may in fact never have existed before on earth </li></ul>
  49. 49. Characteristics of the Immune Response <ul><li>Discrimination between self and nonself </li></ul><ul><li>The ability to recognize and respond to molecules that are foreign or nonself and avoid making a response to those molecules that are self </li></ul><ul><li>The distinction and the recognition of foreign antigen is conferred by specialized cells namely lymphocytes which bear on their surface receptors specific for foreign antigen </li></ul>
  50. 50. Characteristics of the Immune Response <ul><li>Memory </li></ul><ul><li>The ability to recall previous contact with a foreign molecule and respond to it in a learned manner i.e. a more rapid and larger response </li></ul>
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