Immune System
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41 terms
Terms | Definitions |
|---|---|
 lymphocytes | migratory, responsive cells in the immune system that include B cells, T cells, and NK cells |
| B cells | lymphocytes responsible for humoral immunity; they produce antibodies and are contained in lymphoid tissue |
| T cells | lymphocytes responsible for cell-mediated immunity; upon activation they activate cytokines and they can be found either in the bloodstream or lymphoid tissue |
| natural killer (NK) cells | lymphocytes that have cytotoxicity which they use to remove virus-infected or cancerous cells |
| stromal cells of the immune system | non-migratory cells found in lymphatic tissue; include reticular cells, follicular dendritic cells, and interdigitating cells |
| antigen-presenting cells | immune system cells that present MHC's to T cells; includes macrophages, dendritic cells, B cells and others |
| epithelioreticular cells | cells in the thymus that form an interconnecting meshwork with pale ovoid nuclei; secrete thymopoietin which causes T cells to differentiate |
| thymocytes | immature/maturing T lymphocytes in the thymus |
| thymic corpuscles | also known as Hassal's corpuscles; only found in the thymus, they are composed of concentric whorls of degenerating epithelial-reticular cells |
| Peyer's patch | a primary lymphoid tissue (GALT, or gut associated lymphoid tissue) found in the ileum and appendix of the young of some species such as ruminants, pigs, and carnivores |
| secondary lymphoid organs | organs that sustain mature lymphocytes and initiate an immune response; include lymph nodes, the spleen, and MALT |
| hilus | an indentation on the border of a lymph node where blood vessels enter and efferent lymphatic vessels leave |
| capsule | a layer of dense irregular connective tissue and sometimes smooth muscle, below the subcapsular sinus and parenchyma in a lymph node and below the visceral peritoneum (made of mesothelium) in the spleen |
| trabeculae | projections of the capsule that reach into the parenchyma of a lymph node or the spleen |
| reticular meshwork | collagen fibers within a lymph node or the spleen that form a support network; the spaces between are known as lymph sinuses |
| cortex | the outer portion of a lymph node; contains lymphatic follicles (nodules), cortical sinuses, and a paracortical region with diffuse lymphoid tissue |
| lymphatic follicles (nodules) | a close aggregation of lymphocytes (almost always B cells) in the cortex of lymph nodes; can either be primary (unstimulated) or secondary (with a germinal center and mantle) |
| reaction center | the name for a secondary lymphatic follicle that has an abundance of macrophages |
| cortical sinuses | spaces between the follicles in the cortex of lymph nodes that drain fluid from the subcapsular space to the medulla |
| paracortical region (diffuse lymphoid tissue) | tissue that surrounds cortical follicles; is composed of thymus-derived T cells (thymus-dependent zone), and has many venules with high epithelium |
| medulla | the inner portion of a lymph node; contains medullary chords of diffuse lymphoid tissue (mostly B cells) and medullary sinuses |
| spleen | the largest lymphoid organ; specializes in filtering blood and has a hilus and other structures similar to lymph nodes |
| white pulp | in the spleen, lymphocyte-rich tissue that is composed of PALS and splenic follicles |
| PALS (periarterial lymphatic sheaths) | rings of diffuse lymphoid tissue (mostly T cells) around "central arteries" |
| splenic follicles | also known as lymphatic follicles or nodules; are a concentration of B cells with a germinal center located as an extension of PALS around a central artery |
| red pulp | in the spleen, remaining non-lymphocyte tissue that appears loose and red because of numerous red blood cells; composed of venous sinuses and splenic cords |
| venous sinuses | in the red pulp of the spleen, a collection of capillaries that have many discontinuities in the endothelium and are packed with red blood cells |
| splenic cords | in the red pulp of the spleen, the areas between venous sinuses that contain all elements of circulating blood and lymphocytes |
| marginal zone | in the spleen, the area between the red pulp and white pulp; it has B cells and macrophages and blood drains through it so it is an important cite for antigenic monitoring |
| central arteries | arteries of the spleen located in the white pulp; blood flows from the trabecular arteries into the central arteries |
| penicillus | arteries of the spleen located in the red pulp; blood flows to them after going through central arteries |
| cloacal bursa (of fabricus) | a special lymphoid organ only found in birds that is equivalent to the Peyer's patch in other species |
| pharyngeal tonsil | accumulations of lymphoid tissue in the appendix and adenoids of nasopharynx |
| lingual tonsil | accumulation of lymphoid tissue at the root of the tongue |
| sheathed (ellipsoid) capillaries | capillaries of the spleen which have markedly thickened sheaths; after the penicilliary arterioles and before the terminal capillaries |
| terminal capillaries | in the spleen, capillaries lined with continuous epithelium that either drain into venous sinuses (closed theory) or the reticulum of the red pulp (open theory) |
| defensive spleen | found in humans and lagomorphs; an organ characterized by little muscle and abundant lymphatic tissue |
| storage spleen | found in dogs, cats and horses; an organ characterized by lots of muscle and trabeculae |
| intermediate spleen | found in ruminants and swine; an organ characterized as intermediate between defensive and storage spleens |
| mucosa-associated lymphoid tissue (MALT) | clusters of nodular and diffuse lymphoid tissue near mucous membranes; tonsils are an example |
| palatine tonsil | lymphatic tissue found in the connective tissue around the lining of the mouth |
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