| Anitschkow cell | A large mononuclear cell found in connective tissue of the heart wall in inflammatory conditions, especially in the Aschoff body. The ovoid nucleus contains a central chromatin mass appearing as a wavy bar in longitudinal section. Synonym: Anitschkow cell, Anitschkow myocyte, caterpillar cell. (05 Mar 2000) |
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| anterior horn cell | Synonym for motoneuron. (18 Nov 1997) |
| antibody-dependent cell cytotoxicity | The phenomenon of antibody-mediated target cell destruction by non-sensitised effector cells. The identity of the target cell varies, but it must possess surface IgG whose fc portion is intact. The effector cell is a "killer" cell possessing fc receptors. It may be a lymphocyte lacking conventional b- or T-cell markers, or a monocyte, macrophage, or polynuclear leukocyte, depending on the identity of the target cell. The reaction is complement-independent. (12 Dec 1998) |
| antibody-forming cell | <immunology> B-cells (plasma cells) that are dedicated to producing secreted antibodies. (09 Feb 1998) |
| antibody producing cell | <immunology> A lymphocyte of the B series synthesising and releasing immunoglobulin. Equivalent to plasmacyte and plasma cell. (18 Nov 1997) |
| 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) |
| 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) |