17.0, 18.0 IMMUNE SYSTEM

a)Define and use properly the following words: Lines of defense, Primary lymphatic organs, Secondary Lymphatic organs, Innate immune cells, Innate immune system, Adaptive immune system, Immune system cells, Parenchymal cells, Antigen receptor cells, Natural Killer Cells (NK), Antigen presenting cells, Macrophages, Dendritic cells, Follicular dendritic cells, Interdigitating dentritic cells, Supporting stromal cells, Reticular cells, Epithelial reticular cells, Primary lymphatic organs, Bone marrow, Thymus, Cortex, Epithelial reticular, Blood-Thymus-Barrier, Medulla, Tingible body macrophages, Epithelial reticular cells, Thymic corpuscles (Hassall’s corpuscles), Interdigitating dendritic cells, Post capillary venules, Corticomedullary junction, Cloacal bursa, Secondary lymphatic organs, Immune System Circulation, Lymphatics, Discontinuous basal lamina, Afferent lymphatics, Efferent lymphatics, Diffuse Lymphatic Tissue, Dense Lymphatic Tissues, Nodules, Tonsils, Lymph nodes, Spleen, Hemal nodes, Mucosa associated lymphatic tissue (MALT), Nasal Associated Lymphatic Tissue (NALT), Gut associated lymphatic tissue (GALT), Microfold (M) cells, Bronchiolar associated lymphatic tissue (BALT), Lymph node, Capsule , Subcapsular sinus, Reticular cells and fibers, Cortex, Lymphoid nodules, B-cell zone, Germinal center, Mantle, Cortical sinuses, Subcapsular sinus, Paracortical zone, T-cell zone, Paracortical sinuses, Medulla, Medullary cords, Medullary sinus, Afferent lymphatics, Efferent lymphatics, Spleen, Red pulp, Capsule, Splenic sinuses, Splenic cords, Hemosiderin, White pulp, Lymphatic nodules, B-cell zones, Germinal centers, Efferent lymphatics only, Periarterial lymphatic sheaths (PALS), Diffuse lymphatic tissue, T-cell concentration, Marginal zone, Reticular network, Circulatory pathways.

b)Describe and associate basic structure/function for the following: all structures listed above.

c)Identify by microscopy:B-Lymphocytes, T-Lymphocytes, B-cell zones, Biological barrier, Blood-thymus-barrier, Bronchus-associated (BALT), Cell-mediated immunity, Cortex, Cortical sinuses, Dendritic cells, Dense Lymphatic Tissue, Diffuse Lymphatic Tissue, Efferent lymphatics only, Follicular dendritic cells, Germinal center, Gut-associated Lymphatic Tissue (GALT), Hemosiderin, Lymph nodes, Macrophages, Mantle, Marginal sinus, Marginal zone, Mechanical barrier, Medulla, Medullary cords, Medullary sinus, Mucosal Associated Lymphatic Tissues (MALT), Nodules, Paracortical sinuses, Paracortical zone, Periarteriolar lymphatic sheaths (PALS), Phagocytosis, Primary lymphatic organs, Peyer’s patch, Red Pulp, Reticular network, Secondary Lymphatic Organs, Secondary Lymphatic Tissues, Spleen, Splenic cords, Splenic sinuses, Subcapsular sinus, T- Lymphocytes, Thymic corpuscles-Hassall’s corpuscles, Thymus, Tingible body macrophages, Tonsils, Trabeculae, White Pulp.

IMMUNE SYSTEM

I.Main lines of defense:

  1. Protective surface mechanisms
  2. Organs
  3. Primary lymphatic organs:
  4. Bone marrow
  5. Thymus
  6. Cloacal bursa (birds)
  7. Secondary Lymphatic organs
  8. Diffuse Lymphatic tissues
  9. Dense Lymphatic tissues
  10. Mucosal associated lymphatic tissue
  11. Lymph nodes
  12. Spleen
  13. Hemal nodes
  1. Innate immune system = Cells:
  2. Neutrophils,
  3. eosinophils,
  4. basophils,
  5. macrophages,
  6. histiocytes
  7. mast cells.
  1. Innate immune system = Proteins and peptides:
  2. Complement,
  3. acute phase proteins
  4. cytokines
  1. Adaptive immune system
  2. Cellular response: T cell response
  3. Humoral response: B cell response

II.Cells of the immune system:

  1. Parenchymal or functional cells
  2. Antigen receptor cells
  3. Can recognize by light microscopy
  4. Look at nucleus; then cytoplasm
  5. Specific types require immunohistochemistry
  6. T- Lymphocytes
  7. Cell-mediated immunity
  8. B- Lymphocytes
  9. Humoral immune response; circulating antibodies
  10. NK- Cells
  11. Generally rare, more difficult to recognize
  12. Use immunohistochemistry to recognize
  13. Activated; can be larger with some granules, but round nucleus
  14. Cytotoxic
  15. Target tumors; virus-infected cells; altered “self” molecules
  1. Antigen presenting cells
  2. Macrophages
  3. Mononuclear phagocytes
  4. Large nucleus; often folded; large cytoplasm; can have foamy appearance
  5. Process antigens; present to T cells; active in phagocytosis
  6. Resident (Fixed)
  7. Histiocyte (connective tissue)
  8. Osteoclast (bone)
  9. Sinusoidal (spleen)
  10. Microglial (neural tissue)
  11. Kupffer cells (liver)
  12. Alveolar macrophages (lung)
  13. Dendritic cells
  14. Long cytoplasmic processes (not seen by light microscopy)
  15. Look like T-cells within the epithelium
  16. Follicular dendritic cells
  17. Stromal cells within B-cell areas of lymphatic tissue
  18. Traps antigens
  19. Interdigitating dentritic cells
  20. Lymph nodes, thymic medulla, spleen
  21. Langerhans cells of the skin
  22. Present antigen to T-cells
  1. Supporting stromal cells:
  2. Reticular cells
  3. Fibroblast-like
  4. Reticular fibers
  5. All lymphatic organs, except thymus and bursa
  6. Epithelial reticular cells
  7. Thymus and bursa only
  8. No reticular fibers

III.PRIMARY Organs AND TISSUES of the Immune system

  1. Bone marrow
  2. Stem cells for T and B-lymphocytes
  3. B-lymphocyte differentiation
  1. Thymus
  2. Origin and Function
  3. Outgrowth of epithelium (endoderm)
  4. 3rd pharyngeal pouch
  5. Lymphocyte stem cells migrate from bone marrow during fetal life
  6. Stem cells produce T-cells
  7. Lymphocyte graveyard
  8. Regress (involution) after puberty
  9. A school to educate immature immune system "T" cells.
  1. Cortex
  2. Epithelial reticular
  3. Large pale nuclei
  4. Long branching cytoplasmic processes
  5. Connected by desmosomes
  6. Form barrier
  7. Surround lymphoblasts (committed stem cells)
  8. Medulla
  9. T-cells migrate to center for maturation
  10. Tingible body macrophages
  11. Eliminate dead T-cells
  12. Epithelial reticular cells
  13. Very large
  14. Thymic corpuscles (Hassall’s corpuscles)
  15. Numerous cells that die and calcify
  16. “2005 issue of Nature, researchers at The University of Texas M. D. Anderson Cancer Center found that Hassall's corpuscles produce chemical signals that instruct dendritic cells in the thymus to induce development of these regulatory T cells - the critically important immune system cells that patrol the body looking for "bad' T cells that can produce autoimmune disease. These mysterious little structures in the thymus are responsible for producing the T cell policemen that our bodies depend so heavily on," Yong-Jun Liu.
  17. Interdigitating dendritic cells
  18. Blood supply, lymph and nerves
  19. Arteries penetrate connective tissue septa
  20. Form capillary network in cortex
  21. Post capillary venules in corticomedullary junction
  22. Site for T cell entry into blood
  23. T cells travel to lymphatic tissues
  24. Blood-thymus-barrier
  25. Continuous endothelium
  26. Perivascular connective tissue
  27. Epithelial reticular cell process sheath
  28. Decreases access of circulating antigens
  1. Cloacal bursa
  2. Birds
  3. Original discovery of B-cells

IV.Secondary Lymphatic organs AND TISSUES OF THE IMMUNE SYSTEM

  1. Introduction to Secondary Lymphatic Tissues
  1. Immune System Circulation
  2. Blood vessels carry antigens and cellular elements
  3. Lymph vessels (lymphatics) carry intercellular fluid and WBCs
  4. Capillaries (large, mold to the tissue)
  5. Larger vessels are like arteries with muscle
  6. Discontinuous basal lamina and sometimes absent
  7. Absent or modified in tissues lacking ground substances derived from Hyaluronic acid
  8. CNS, eye, bone marrow, cartilage, red pulp of spleen, liver lobules, tonsils.
  9. Afferent lymphatics carry lymph towards an organ
  10. Efferent lymphatics carry lymph away from an organ
  11. Activity includes antigen processing and antibody production
  12. Antigen interaction with lymphocytes ONLY in secondary tissues
  13. Antigen entry and exposure
  14. Designed to be guarded by lymphoid tissue at entry points
  15. Oral, gut, respiratory
  1. Diffuse Lymphatic Tissue
  2. Network of reticular cells
  3. Mixed in with nodules to provide filtering and antigen exposure to cells
  4. associated with reticular fibers that enmesh White Blood Cells and macrophages
  5. Found in the following sites:
  6. Between lymphatic nodules
  7. In medullary cords and deep cortex of lymph and hemal nodes and lymphatic sheaths of spleen
  8. Scattered throughout loose connective tissues wherever lymphocytes, plasma cells, macrophages accumulate.
  1. Dense Lymphatic Tissues or Mucosal Associated Lymphatic Tissues (MALT) or nodules
  2. Tonsils
  3. Bronchus-associated (BALT)
  4. Gut-associated (GALT)
  5. Lymph nodes
  6. Filters interstitial fluids
  7. Lymphatics drain all organs and skin
  8. Infectious agents travel to lymph nodes for antigen interaction with lymphocytes
  9. Spleen
  10. Filters the blood
  11. Hemal nodes
  12. Blood sinuses

V.Dense lymphatic tissue -Mucosa associated lymphatic tissue (MALT)

  1. Similar to lymph node but no capsule; not organ
  2. Sometimes called MALT (Mucosa Associated Lymphatic Tissue)
  3. Primary lymphatic nodules, with specific epithelial (mucosal) covering
  4. Tightly packed lymphocytes
  5. No afferent lymphatic vessels, but have efferent lymphatics
  6. Tonsils
  7. Covered with stratified squamous or respiratory epithelium
  8. Nasal Associated Lymphatic Tissue
  9. NALT
  10. Covered by stratified squamous or respiratory epithelium
  11. GALT (gut associated lymphatic tissue)
  12. Nodules, lymphoid cells, mucosa
  13. Specialized cells form epithelial nodule associated epithelium
  14. Microfold (M) cells
  15. Screen antigen in the gut
  16. Fewer goblet cells here
  17. BALT (Bronchiolar associated lymphatic tissue)
  18. Nodules and lymphoid cells; mucosa
  19. Respiratory epithelium

VI.Lymph node

  1. Function
  2. This is an ORGAN
  3. Forms lymphocytes
  4. In line filter of interstitial fluids or lymph
  5. Phagocytosis of foreign material
  6. Produce antibodies (Plasma cells)
  1. Structure:
  2. Capsule
  3. Subcapsular sinus
  4. Reticular cells and fibers
  5. Capillary network surround nodules in cortex
  1. Cortex
  2. Lymphoid nodules
  3. B cell zone
  4. Germinal center
  5. Large euchromatic lymphocytes
  6. Mantle
  7. Surrounds germinal center
  8. Contains smaller dense lymphocytes
  9. Cortical sinuses
  10. Between lymphatic nodules
  11. Continuous with subcapsular sinus
  12. Paracortical zone
  13. T-cell zone
  14. Paracortical tissue
  15. Reticular cells, Antigen presenting and lymphocytes
  16. Surrounds nodules
  17. Paracortical sinuses
  18. Extend from cortical into medulla
  1. Medulla
  2. Less cellular; lacks nodules
  3. Exception is pig (nodules in medulla)
  4. Medullary cords
  5. Reticular cells, antigen presenting, lymphocytes
  6. Plasma cells, macrophages
  7. T-cell area
  8. Medullary sinus
  9. Reticular cells and fibers
  10. Lymph flow
  11. Flows through sinuses NOT blood
  12. Afferent lymphatics
  13. Bring lymph into the lymph node
  14. Enter capsule
  15. Empty into subcapsular sinus
  16. Enter cortical sinus and Paracortical
  17. Enter medullary sinuses
  18. Efferent lymphatics
  19. Lymph leaves node at the hilus
  20. Should observe lymphatic valves
  21. Prevent back flow
  1. Species differences
  2. Pig (porcine)
  3. Lymph node of pig is inverted
  4. Nodules are in the center of the lymph node.

VII.Spleen

  1. General Information
  2. Function: filters the blood
  3. Thick connective tissue capsule
  4. Cortex and Medulla areas
  5. Two zones; Red and White Pulp
  6. Can form RBCs
  7. Destruction of old or damaged RBCs
  8. Formation of WBCs
  9. Blood storage
  10. Species differences
  11. Some horses have extra storage (50%)
  12. Increases thickness of blood
  13. Stronger hearts
  14. Splenic contraction gives oxygen boost
  15. Dogs and cats store RBC, too
  16. Humans store platelets
  1. Capsule
  2. Thick connective tissue
  3. Dense irregular
  4. Smooth muscle layer
  5. Trabeculae
  6. Connective tissue
  7. Collagen, elastin, smooth muscle
  8. Blood vessels, lymph, nerve
  9. Red Pulp
  10. Most of the parenchyma
  11. Blood, Erythrocytes
  12. Splenic sinuses
  13. Wide channels
  14. Long longitudinal endothelial cells, contractile
  15. Slits form upon contraction
  16. Allow RBCs to migrate (squeeze) into cords
  17. Fenestrated basal lamina supported by reticular fibers
  18. Splenic cords
  19. Between sinuses
  20. Network of fibers, reticular cells
  21. RBCs, macrophages, lymphocytes, leukocytes
  22. Build up of iron from breakdown of old RBCs
  23. ‘Hemosiderin’
  24. brown pigment of hemoglobin breakdown
  25. Filtration
  26. Mechanical
  27. by reticular fibers and endothelial cells
  28. Biological
  29. Macrophages and Neutrophils
  30. Species differences
  31. Ruminant and porcine
  32. More smooth muscle
  33. Horse and dog
  34. Myofibroblasts (contractile)
  35. Plus smooth muscle
  36. White pulp
  37. Lymphatic nodules and diffuse lymphatic tissue
  38. Nodules
  39. B-cell zones
  40. Germinal centers +/-
  41. Efferent lymphatics only
  42. Periarterial lymphatic sheaths (PALS)
  43. Diffuse lymphatic tissue
  44. Line the white pulp arteries (can see in microscope)
  45. T-cell concentration
  46. Mixture of T and B as you near the nodules
  47. Other cells
  48. Macrophages, dendritic cells, reticular cells
  49. Species differences
  50. Cat, ruminant
  51. Less nodules, short PALS; large macrophage sheaths
  52. Horse, dog, pigs
  53. Numerous nodules
  54. Numerous PALS
  55. Marginal zone
  56. Between white and red pulp
  57. Flattened reticular cells form concentric layer
  58. Reticular network
  59. Marginal sinus formed
  60. Drain slowly toward venous sinuses of red pulp
  61. Numerous macrophages and B-cells
  62. Extensive antigen and foreign body interaction with lymphocytes and macrophages
  63. Macrophages transport trapped antigens to the PALS
  1. Circulatory pathways in the spleen:

1