| AEM | Academic Emergency Medicine [journal]; analytical electron microscopy; ambulatory electrocardiograph... |
|---|---|
| AM | Academic Medicine [journal]; actomyosin; acute myelofibrosis; adult male; adult monocyte; aerospace ... |
| BMJ | bones, muscles, joints; British Medical Journal |
| CPSC | congenital paucity of secondary synaptic clefts [syndrome]; Consumer Products Safety Commission |
| ERPC | evacuation of retained products of conception |
natural purification (자정 작용
| natural killer cells | Large granular lymphocytes which do not express markers of either T or B-cell lineage. These cells do possess Fc receptors for IgG and can kill target cells using antibody-dependent cell-mediated cytotoxicity. NK cells can also use perforin to kill cells in the absence of antibody. Killing may occur without previous sensitization. Synonym: NK cells. (05 Mar 2000) |
|---|---|
| natural killer cell stimulating factor | <cytokine> A 75 kD heterodimeric cytokine composed of disulfide-bonded 40 kD and 35 kD subunits that was originally identified by its ability to induce cytotoxic effector cells in synergy with less than optimal concentrations of interleukin-2. It is released by macrophages in response to infection and promotes the activation of cell-mediated immunity. Specifically, IL-12 triggers the maturation of Thl CD4 cells, specific cytotoxic T-lymphocyte responses and an increase in the activity of NK cells and consequently, it is the initiator of cell-mediated immunity. It enhances the lytic activity of NK cells, induces interferon production, stimulates the proliferation of activated T-cells and NK cells. Is secreted by human B lymphoblastoid cells (NC 37). May play a role in controlling immunoglobulin isotype selection as it also inhibits IgE synthesis (even in the presence of anti-IFN monoclonal antibody) and as a growth factor for activated CD4+ and CD8+ T-cells independently of interleukin-2, and for CD56+ NK cells but not resting peripheral blood mononuclear cells or resting or activated tonsillar B-cells. It is likely that interleukin 12 has a major role in protective immunity against viruses and is under study as an immunotherapy in HIV infection. Formerly referred to as cytotoxic lymphocyte maturation factor. Acronym: IL-12 (12 Dec 1998) |
| natural language processing | Computer processing of a language with rules that reflect and describe current usage rather than prescribed usage. (12 Dec 1998) |
| natural mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
| natural passive immunity | Immunity conferred by the mother on the foetus or newborn. (14 Nov 1997) |
| natural pigment | A naturally occurring coloured compound; absorbs light in the visible range of the electromagnetic spectrum. Compare: structural colour. Synonym: biochrome. (05 Mar 2000) |
| natural selection | The hypothesis that genotype environment interactions occurring at the phenotypic level lead to differential reproductive success of individuals and hence to modification of the gene pool of a population. (18 Nov 1997) |
| immunity, natural | The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from non-specific mechanisms such as genetic endowment, naturally occurring antiviral and bactericidal substances, phagocytosis, and constitutional factors such as body temperature, oxygen tension, and age. (12 Dec 1998) |
| killer cells, natural | Cells responsible for spontaneous cytotoxicity of a variety of tumour cells without prior immunization. These natural killer cells are found in non-immune humans and experimental animals and are thought by some to be the same as killer cells (killing by antibody-dependent cell cytotoxicity), but they can also kill in the absence of antibody. (12 Dec 1998) |
| biological products | Complex pharmaceutical substances, preparations, or agents of organic origin, usually obtained by biological methods or assay, that depend for their action on the processes affecting immunity. They are used especially in diagnosis and treatment of disease (as vaccines or pollen extracts). Biological products are differentiated from biological factors in that the latter are compounds with biological or physiological activity made by living organisms. (12 Dec 1998) |
| blood products | Biopharmaceutical products purified from human blood, such as the blood clotting factor VIII used to treat haemophiliacs. (Recombinant factor VIII is also on the market.) The term also refers to biopharmaceuticals that act on blood or the cells that make blood. These products are often produced by the cells themselves, but in such tiny amounts that extracting them from blood is impractical, and so they are genetically engineered. (14 Nov 1997) |
| gene products, env | Retroviral proteins, often glycosylated, coded by the envelope (env) gene. They are usually synthesised as protein precursors (polyproteins) and later cleaved into the final products by a viral protease. (12 Dec 1998) |
| gene products, gag | Proteins coded by the retroviral gag gene. The products are usually synthesised as protein precursors or polyproteins, which are then cleaved by viral proteases to yield the final products. Many of the final products are associated with the nucleoprotein core of the virion. Gag is short for group-specific antigen. (12 Dec 1998) |
| gene products, nef | Products of the HIV nef gene (formerly 3'-orf gene). The products trans-suppress viral replication and function as negative regulators of transcription. Nef stands for negative factor. (12 Dec 1998) |
| gene products, pol | Retroviral proteins coded by the pol gene. Often synthesised as a gag-pol fusion protein (fusion proteins, gag-pol) and later cleaved into final products that include reverse transcriptase, endonuclease/integrase, and viral protease. Pol is short for polymerase, the enzyme class of reverse transcriptase. (12 Dec 1998) |