| C3a | activated third component of complement |
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| C4 | fourth cervical nerve; fourth cervical vertebra; fourth component of complement |
| C4a | activated fourth component of complement |
| C5 | fifth cervical nerve; fifth cervical vertebra; fifth component of complement |
| C6 | sixth cervical nerve; sixth cervical vertebra; sixth component of complement |
| 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) |
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