Term
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Definition
| the chief cellular component of lymphatic tissue; 70% (mainly T-lymphocytes) circulate from systemic circulation to lymphatics then return; 30% (immature or activated T's and B's) do not circulate and migrate to target tissues (connective tissue lining the respiratory) |
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Term
| where do T-lymphocytes arise? |
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Definition
| arise from bone marrow as stem cells and travel to the thymus where they differentiate |
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Term
| what percent of lymphocytes are T-lymphocytes? |
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Definition
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Term
| what do helper T-cells do? |
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Definition
| interact with NK cells, macrophages, B-cells, and CD8+ T cells |
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Term
| what do cytotoxic T-cells do? |
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Definition
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Term
| where are MHC-I molecules expressed? |
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Definition
| all nucleated cells and platelets |
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Term
| where are MHC-II molecules expressed? |
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Definition
| on macrophages, dendritic cells and B-cells |
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Term
| what are regulatory (suppressor) T-lymphocytes? |
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Definition
| CD4+ or CD8+; suppress ability of T-cells to initiate immune responses |
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Term
| where are gamma/delta T-lymphocytes located? |
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Definition
| positioned at interfaces of the external and internal environments (epithelial cell surfaces of skin, oral mucosa, intestines, vagina) and serve as first line of defense against invading organisms |
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Term
| Following activation, what do B-lymphocytes differentiate to? |
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Definition
| antibody secreting plasma cells |
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Term
| what are natural killer cells? |
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Definition
| genetically programmed to recognize transformed cells and kill them using perforins and granzymes resulting in death by apoptosis |
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Term
| what are the primary lymphatic organs for lymphocyte development and differentiation? |
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Definition
| bone marrow/GALT and Thymus |
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Term
| what are lymphocytes programmed to do? |
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Definition
| recognize a single antigen out of an infinite number of possible antigens in a process called Antigen-Independent Proliferation and Differentiation |
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Term
| what is the initial response to antigens? |
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Definition
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Term
| what are the main 'players' in inflammation response? |
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Definition
| granulocytes and macrophages |
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Term
| what are lymphatic vessels? |
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Definition
| network of blind capillaries in loose connective tissue beneath the epithelium of the skin and mucous membranes |
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Term
| how permeable are the walls of lymphatic vessels? |
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Definition
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Term
| what passes through the lymphatic vessels and into lymph nodes? |
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Definition
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Term
| what is the function of lymph? |
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Definition
| antigens are trapped by follicular dendritic cells and are then presented on their surface where cells known as antigen presenting cells (APC) process the antigen and present to T or B- lymphocytes |
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Term
| True or False: lymphocytes move from blood to lymphoid tissue and back to blood during different stages of development |
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Definition
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Term
| what vessel allows for the entry of the lymphocytes (in lymph fluid) to enter the lymph node? |
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Definition
| afferent lymphoid vessels |
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Term
| what allows entry of lymphocytes (in the blood) to enter the lymph node? |
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Definition
| the walls of postcapillary venules |
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Term
| what does diffuse lymphatic tissue and lymphatic nodules function to do? |
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Definition
| guard the body against pathogens and are the sites for initial immune responses |
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Term
| what are lymphatic nodules? |
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Definition
| localized concentrations of lymphocytes in walls of alimentary canals, respiratory passages and genitourinary tract |
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Term
| primary lymphatic nodules are composed of? |
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Definition
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Term
| what are some of the supporting structures of the lymph node? |
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Definition
| capsule, trabeculae, reticular tissue |
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Term
| what do afferent lymphatic vessels carry? |
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Definition
| carry lymph toward the node and enter at various convex points around the lymph node |
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Term
| what do efferent lymphatic vessels carry? |
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Definition
| carry the lymph away from the node and exit at the hilum which serves as the entrance for blood vessels and nerves |
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Term
| what are reticular cells? |
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Definition
| fibroblast-like, secrete type III collagen, also attract T-cells, B-cells and macrophages |
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Term
| what are dendritic cells? |
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Definition
| bone marrow-derived, phagocytic, macrophage, antigen presenting cells expressing MHC-I and MHC-II |
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Term
| which are more efficient: macrophages or dendritic cells? |
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Definition
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Term
| what are follicular dendritic cells? |
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Definition
| in germinal centers with cytoplasmic processes which interdigitate between B-cells; do not present antigen as they lack MHC molecules |
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Term
| what are high endothelial venules? |
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Definition
| contain receptors for antigen primed B and T cells and signal them from the blood stream to enter via a process called diapedesis; T-cells go to the deep cortex, B-cells migrate to nodular cortex |
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Term
| what percent of the T-cells in the thymus become mature T-cells and leave the thymus? |
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Definition
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Term
| MHCII is expressed in high levels in which types of cells? |
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Definition
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Term
| MHCI is found in high levels in which types of cells? |
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Definition
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Term
| what is the function of the lymph node? |
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Definition
| phagocytosis of particulate materials (antigen) by phagocytic cells in the lymph node is an important step in initiating immune responses |
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Term
| True or false: plasma cells migrate to medullary cords and produce antibody, which flows in and out of lymph node. |
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Definition
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Term
| describe the thymus and where it was developed |
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Definition
| bilobed; developed from the 3rd and 4th oropharyngeal pouch; multipotential lymphoid stem cells move from bone marrow into thymus where they develop into immunocompetent T-cells; reduces in size by puberty and lymphatic tissue is replaced by adipose tissue |
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Term
| where are type I epithelioreticular cells located? |
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Definition
| boundary of cortex and capsule and separate thymic parenchyma and trabeculae |
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Term
| where are type II epithelioreticular cells located? |
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Definition
| in cortex and compartmentalize areas of developing T-cells and serve to educate them; express both MHC I and II |
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Term
| where are type III epithelioreticular cells found? |
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Definition
| boundary of cortex and medulla and serve to educate T-cells as type II. Express MHC I and II |
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Term
| Approximately what percent of T-cells are phagocytized by macrophages since they did not meet the correct thymic education? |
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Definition
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Term
| where are type IV epithelioreticular cells located? |
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Definition
| between the cortex and medulla next to type III and help create barrier at corticomedullary junction |
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Term
| where are type V epithelioreticular cells located? |
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Definition
| throughout the medulla and help to compartmentalize groups of lymphocytes in the medulla |
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Term
| where are type VI epithelioreticular cells located? |
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Definition
| form Hassal's corpuscles which are closely packed, concentric bundles which possess keratohyalin granules, intermediate filament and lipid droplets and are joined by desmosomes; they are postulated to produce interluekins |
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Term
| describe T-Cell education |
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Definition
| characterized by expression and deletion of specific surface CD antigens |
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Term
| CD1 expression in T-Cell education characterizes what stage? |
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Definition
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Term
| which types of cells eventually leave the thymus and "graduate" in T-Cell education? |
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Definition
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Term
| describe the spleen and its functions |
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Definition
| largest of lymphoid organs, contains a rich blood supply, with lymphocytes, channels, meshwork of reticular cells and fibers, macrophages and dendritic cells |
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Term
| how much blood does the human spleen normally contain? |
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Definition
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Term
| what is the spleen enclosed by? |
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Definition
| dense connective tissue capsule from which trabeculae extend into the parenchyma of the organ |
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Term
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Definition
| lymphatic tissue, mostly lymphocytes associated with central splenic artery |
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Term
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Definition
| splenic sinuses separated by splenic cords consisting of loose meshwork of reticular cells, fibers containing large numbers of erthrocytes, macrophages, lymphocytes, dendritic cells, plasma cells and granulocytes. Splenic macrophages phagocytose damaged red blood cells, hemoglobin breakdown and iron reclamation |
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Term
| what are the components of the spleen? |
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Definition
| Endothelial cells line the splenic sinuses and run parallel to the direction of the vessel; Intercellular spaces allow blood cells to pass in and out of the sinuses; Strands of basal lamina loop around the outside of the sinus |
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Term
| describe open splenic circulation |
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Definition
| Central artery branches to the white pulp and sinuses at the perimeter (marginal sinuses) and continues into red pulp, branching to straight arterioles (penicillar arterioles). Circulation continues as arterial capillaries, some of which are surrounded by macrophages (sheathed capillaries) and then empties directly into reticular meshwork of the splenic cords. |
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Term
| describe closed splenic circulation |
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Definition
| In other species, the blood from the sheathed capillaries passes directly to the splenic sinuses of the red pulp. |
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Term
| what is the immune functions of the spleen? |
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Definition
Ag presentation
Activation & Proliferation of B and T-cells
Antibody production
Removal of antigens from blood |
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Term
| what is the hemopoietic function of the spleen? |
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Definition
Removal of old and damaged RBC & platelets
Iron removal
Formation of erythrocytes
Blood storage/reservoir (esp. RBC’s in some species) |
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