| amphotropic packaging cell lines | <cell culture, molecular biology> Clonal entities that express genes or act as viral vectors that infect cell lines to stably infect and then express genes of choice. Usually an amphotropic virus. (04 Nov 1997) |
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| anaemia, sickle cell | A disease characterised by chronic haemolytic anaemia, episodic painful crises, and pathologic involvement of many organs. It is the clinical expression of homozygosity for haemoglobin s. (12 Dec 1998) |
| anaplastic cell | A cell that has reverted to an embryonal state, an undifferentiated cell, characteristic of malignant neoplasms. (05 Mar 2000) |
| anaplastic large cell lymphoma | <tumour> A form of lymphoma characterised by anaplasia of cells, sinusoidal growth, and immunoreactivity with CD30 (Ki-1 or Ber-H2). Synonym: Ki-1+ lymphoma. (05 Mar 2000) |
| animal cell culture | <cell culture> Mammalian cells are fragile and harder to grow than other cell types, but their large-scale culturing is an economic boon because it allows for the production of proteins that are otherwise difficult or expensive or unethical to extract from living organisms. The cells are immobilised on a substrate and then perfused with culture medium, The cells are in a free suspension which is very gently mixed and aerated. (12 Nov 1997) |
| animal cell immobilisation | <cell culture> Animal cells are widely used in biotechnology to produce genetically engineered proteins. However, they are more fragile than bacterial cells, and immobilising the cell facilitates the fermentation process. Many animal cells stick down flat on a suitable surface, hugging it as they would hug other cells or connective matrices in the body. If grown on suitable plastic surfaces, on glass or many ceramics, these cells will stick to them. In this way, they are easier to grow. (14 Nov 1997) |
| animalised cell | <zoology> The 8-16 cell early blastula of sea urchins has animal and vegetal poles, by manipulating the environmental conditions it is possible to shift more cells from vegetal to animal in their characteristics. (12 Nov 1997) |
| 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) |
| 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) |