| antigen presenting cell | A cell that carries on its surface antigen bound to MCH Class I or Class II molecules and presents the antigen in this context to T-cells. Includes macrophages, endothelium, dendritic cells and Langerhans cells of the skin. See: MHC restriction, histocompatibility antigens. (18 Nov 1997) |
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| antigen-responsive cell | A small lymphocyte that, although not itself an immunologically activated cell, responds to antigenic (immunogenic) stimulus by a process of division and differentiation that results in the production of immunologically activated cells. Synonym: antigen-responsive cell. (05 Mar 2000) |
| antigen-sensitive cell | A small lymphocyte that, although not itself an immunologically activated cell, responds to antigenic (immunogenic) stimulus by a process of division and differentiation that results in the production of immunologically activated cells. Synonym: antigen-responsive cell. (05 Mar 2000) |
| antiparietal cell antibody | <immunology> A serologic blood test which measures the presence of antibodies to gastric parietal cells. Less than 2% of the general population will be antibody positive although this can be higher in the elderly. Approximately 90% of individuals with pernicious anaemia will be antibody positive. A positive result may also be seen in atrophic gastritis, gastric ulcer, thyroid disease, iron deficiency anaemia and diabetes. (13 Jan 1998) |
| antipodal cell | <plant biology> Three cells of the embryo sac in angiosperms, found at the end of the embryo away from the point of entry of the pollen tube. (13 Jan 1998) |
| apolar cell | A neuron without processes. (05 Mar 2000) |
| APUD cell | <pathology> A group of apparently unrelated endocrine cells found throughout the body which have a number of similar characteristics and which make a number of hormones with similar structures (including serotonin, epinephrine, dopamine, neurotensin, and norepinephrine. See: Amine Precursor Uptake and Decarboxylation. (10 Jan 1998) |
| argentaffin cell | So called because they will form cytoplasmic deposits of metallic silver from silver salts. Their characteristic histochemical behaviour arises from 5 HT, which they secrete. Found chiefly in the epithelium of the gastrointestinal tract (though possibly of neural crest origin) their function is rather obscure, although there is a widely distributed family of such paracrine (local endocrine) cells (APUD cells). (18 Nov 1997) |
| argyrophilic cell | <pathology> Cell's that bind silver salts but that precipitate silver only in the presence of a reducing agent. See: enteroendocrine cells. (05 Mar 2000) |
| Aschoff cell | A large cell component of rheumatic nodules in the myocardium with a characteristic nucleus and relatively little cytoplasm. (05 Mar 2000) |
| Askanazy cell | <pathology> Abnormal thyroid epithelial cells found in auto immune thyroiditis. The cubical cells line small acini and have eosinophilic granular cytoplasm and often bizarre nuclear morphology. Synonym: Hurthle cell, oxyphil cell, oncocyte. (18 Nov 1997) |
| astroglia cell | <pathology> A glial cell found in vertebrate brain, named for its characteristic star like shape. Astrocytes lend both mechanical and metabolic support for neurons, regulating the environment in which they function. See: oligodendrocytes. (18 Nov 1997) |
| atypical cell | Not usual, abnormal. Cancer is the result of atypical cell division. (09 Oct 1997) |
| bag cell neurons | <cell biology> Cluster of electrically coupled neurons in the abdominal ganglion of Aplysia that are homogeneous, easily dissected out and release peptides that stimulate egg laying. (18 Nov 1997) |
| balloon cell | An unusually large degenerated cell with pale-staining vacuolated or reticulated cytoplasm, as in viral hepatitis or in degenerated epidermal cell's in herpes zoster, a large form of nevus cell with abundant nonstaining cytoplasm, formed by vacular degeneration of melanosomes. (05 Mar 2000) |