| MAC complex | complement |
|---|---|
| major histocompatabilty complex | <immunology> A cluster of genes on chromosome 6 concerned with antigen production and critical to transplantation. The MHC includes the human leukocyte antigen (HLA) genes. (12 Dec 1998) |
| major histocompatibility complex | The set of gene loci specifying major histocompatibility antigens, for example HLA in man, H 2 in mice, RLA in rabbits, RT 1 in rats, DLA in dogs, SLA in pigs, etc. Acronym: MHC (18 Nov 1997) |
| VATER complex | A constellation of vertebral defects, anal atresia, tracheoesophageal fistula with oesophageal atresia, and renal and radial anomalies; associated with Fanconi's anaemia. (05 Mar 2000) |
| rancke complex | <radiology> Combination of: calcified peripheral nodule (Ghon lesion), calcified hilar nodes, occurs in 50% of patients with primary TB (12 Dec 1998) |
| ventricular complex | The continuous QRST waves of each beat in the electrocardiogram. (05 Mar 2000) |
| receptor-CD3 complex, antigen, T-cell | Molecule composed of the non-covalent association of the T-cell antigen receptor (receptors, antigen, T-cell) with the CD3 complex (antigens, CD3). This association is required for the surface expression and function of both components. The molecule consists of up to seven chains: either the alpha/beta or gamma/delta chains of the T-cell receptor, and four or five chains in the CD3 complex. (12 Dec 1998) |
| Ghon's complex | Calcification seen in pulmonary parenchyma (usually mid-lung area) and hilar nodes resulting from earlier, usually childhood, infection with tuberculosis. Synonym: Ghon's complex, Ghon's focus, Ghon's primary lesion. (05 Mar 2000) |
| castration complex | A child's fear of injury to the genitals by the parent of the same sex as punishment for unconcious guilt over oedipal feelings, fantasied loss of the penis by a female or fear of its actual loss by a male, unconscious fear of injury from those in authority. Synonym: castration anxiety. (05 Mar 2000) |
| caudal pharyngeal complex | The ultimobranchial body associated with the embryonic fourth and transitory fifth pharyngeal pouches. (05 Mar 2000) |
| vitamin b complex | <chemical> A group of water-soluble substances including thiamine, riboflavin, niacin (nicotinic acid), niacinamide (nicotinamide), the vitamin b6 group (including pyridoxine, pyridoxal, pyridoxamine), biotin, pantothenic acid, folic acid, possibly para-aminobenzoic acid, inositol, vitamin b12, and possibly choline. Chemical name: Vitamin B (12 Dec 1998) |
| central complex | In an enzyme-catalyzed reaction, the structural complex of the enzyme and all of the enzyme's substrates (or the enzyme with all of the enzyme's products) equivalent to the binary complex for a one-substrate enzyme. Compare: binary complex, Michaelis complex. (05 Mar 2000) |
| glycine cleavage complex | A complex of several proteins that catalyze the reversible reaction of glycine with tetrahydrofolate to produce CO2, NH3, and N5,N10-methylenetetrahydrofolate; a deficiency of this enzyme (or one of its subunits) will result in nonketotic hyperglycinaemia. Synonym: glycine synthase. (05 Mar 2000) |
| Golgi complex | <cell biology> Intracellular stack of membrane bounded vesicles in which glycosylation and packaging of secreted proteins takes place. Part of the GERL complex. Synonym: Golgi body, Golgi vesicles, dictyosome (in plants), parabasal body (in flagellate protozoa). (11 Jan 1998) |
| membrane attack complex | <immunology> A term originally used to refer to the heat labile factor in serum that causes immune cytolysis, the lysis of antibody coated cells and now referring to the entire functionally related system comprising at least 20 distinct serum proteins that is the effector not only of immune cytolysis but also of other biologic functions. Complement activation occurs by two different sequences, the classic and alternative pathways. The proteins of the classic pathway are termed components of complement and are designated by the symbols C1 through C9. C1 is a calcium dependent complex of three distinct proteins C1q, C1r and C1s. The proteins of the alternative pathway (collectively referred to as the properdin system) and complement regulatory proteins are known by semisystematic or trivial names. Fragments resulting from proteolytic cleavage of complement proteins are designated with lower case letter suffixes, for example, C3a. Inactivated fragments may be designated with the suffix i, for example C3bi. Activated components or complexes with biological activity are designated by a bar over the symbol for example C1 or C4b, 2a. The classic pathway is activated by the binding of C1 to classic pathway activators, primarily antigen-antibody complexes containing IgM, IgG1, IgG3, C1q binds to a single IgM molecule or two adjacent IgG molecules. The alternative pathway can be activated by IgA immune complexes and also by nonimmunologic materials including bacterial endotoxins, microbial polysaccharides and cell walls. Activation of the classic pathway triggers an enzymatic cascade involving C1, C4, C2 and C3, activation of the alternative pathway triggers a cascade involving C3 and factors B, D and P. Both result in the cleavage of C5 and the formation of the membrane attack complex. Complement activation also results in the formation of many biologically active complement fragments that act as anaphylatoxins, opsonins or chemotactic factors. (05 Jan 1998) |