| complement pathway, alternative | The complement activation sequence initiated by the activation of complement factor c3, which is triggered by the interaction of microbial polysaccharides and properdin without participation of an antigen-antibody reaction. (12 Dec 1998) |
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| complement pathway, classical | The sequential activation of complement, initiated by antigen-antibody complex and the binding of complement factor c1q to the fc region of the antibody. (12 Dec 1998) |
| complement system | A group of more than 20 serum proteins, some of which can be serially activated and participate in a cascade resulting in cell lysis. (05 Mar 2000) |
| complement unit | The smallest amount (highest dilution) of complement that will cause haemolysis of a unit of red blood cells in the presence of a haemolysin unit. Synonym: alexin unit. (05 Mar 2000) |
| component of complement | Any one of the nine distinct protein units (designated C1 through C9 and distributed in the a, b, and g electrophoretic partitions of normal serum) that effect the immunological activities long associated with complement. C1 is a complex of three subunits: C1q, C1r, and C1s. C1q (overbar indicates "active form") activates proenzyme C1r to C1r which activates C1s to C1s (also known as C1 esterase), which converts proenzyme C2 to C2b and produces C4b from C4. C2b combines with C4b to form "classical-complement-pathway C3/C5 convertase" (also known as C3 convertase, C5 convertase, and C42). This enzyme cleaves C3 to C3a and C3b, and C5 to yield C5a and C5b, as does "alternative-complement-pathway C3/C5 convertase" (also known as proenzyme factor B, properdin factor B, C3 proactivator, and heat-labile factor). Complement factor I (also known as C3b or C3b/C4b inactivator) inactivates C3b and C4b by a different proteolytic cleavage. Several autosomal recessive disorders have been identified in which one or more of the complement components have been deficient or completely absent. (05 Mar 2000) |
| heparin complement | The protein component of heparin in blood. (05 Mar 2000) |
| thyrotoxic complement-fixation factor | A form of thyrotoxin; an antigen found most readily in thyroid tissue from thyrotoxic individuals; known to be chemically and immunologically distinct from thyroglobulin, and fixes complement when combined with antibody related to the gamma-globulin fraction of serum. With the exception of extremely small concentrations, the antigen is rarely found in normal glands or in diseased glands that are not associated with thyrotoxicosis; it is probably an intracellular substance (possibly a constituent of the "microsomal fraction"), and does not contain iodine in significant quantity. Not related to the complement-fixation reaction occurring with serum in Hashimoto's disease, in which the antigen is thyroglobulin. (05 Mar 2000) |
| acetyl reduction assay | <investigation> A technique for measuring the nitrogen fixation activity in photosynthetic organisms. It uses a flame ionisation detector and a gas chromatography apparatus to determine the reduction of acetylene to ethylene by the enzyme nitrogenase. (06 May 1997) |
| Ames assay | <procedure> One of a number of procedures used to test substances for likely ability to cause cancer that combines the use of animal tissue to generate active metabolites of the substance with a test for mutagenicity in bacteria. (18 Nov 1997) |
| antibiotic assay | <investigation> A test to determine how sensitive a bacterial or fungal strain is to arange of antibiotics bymeasuring the microbes' ability to grow in astandard dilution of each chemical. (09 Oct 1997) |
| assay | <procedure> The determination of the amount of a particular constituent of a mixture or of the biological or pharmacological potency of a drug. (10 May 1997) |
| bandshift assay | <investigation> An assay for proteins, such as transcription factors, that bind specific DNA sequences. A labelled oligonucleotide corresponding to the recognition sequence is incubated with an appropriate nuclear protein extract and run on a nondenaturing acrylamide gel. Oligonucleotides that have been bound by proteins are retarded relative to those that are unbound. (18 Nov 1997) |
| biological assay | <technique> Once a pharmaceutical protein is isolated from the cells in which it was grown, researchers perform tests to measure the protein's biological activity. It must maintain a certain minimal level of biological activity to be used for animal or clinical testing or, later, for market. Researchers also test to confirm that the isolated protein is identical to the desired protein. (21 Mar 1998) |
| radioimmunoprecipitation assay | Sensitive assay using radiolabelled antigens to detect specific antibodies in serum. The antigens are allowed to react with the serum and then precipitated using a special reagent such as protein a sepharose beads. The bound radiolabelled immunoprecipitate is then commonly analyzed by gel electrophoresis. Radioimmunoprecipitation assay (ripa) is often used as a confirmatory test for diagnosing the presence of HIV antibodies. (12 Dec 1998) |
| radioligand assay | <radiobiology> Quantitative determination of receptor (binding) proteins in body fluids or tissue using radioactively labelled binding reagents (e.g., antibodies, intracellular receptors, plasma binders). (12 Dec 1998) |