PubMed · 10635777
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S Takemura. 1999. [The fifth component of complement, C5].. https://pubmed.ncbi.nlm.nih.gov/10635777/
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Sera genetically deficient in either the alpha-gamma or the beta-subunit of complement component C8 virtually lack haemolytic activity. We have studied the formation and the structural organization of the soluble terminal complement complex (TCC) assembled in these sera following activation with cobra venom factor (CVF). The TCC concentration in the activated C8alpha-gamma and C8beta-deficient samples was 0.2% and 4%, respectively, when compared with zymosan-activated normal serum. TCC was purified from the activated C8beta-deficient samples by affinity chromatography and analysed by immunoblotting and enzyme immunoassay. No C8beta was detected in one TCC preparation, while 7% of the normal level was present in the other. The level of the other terminal components, including that of C8alpha-gamma, was normal. The ability of C8alpha-gamma to promote the assembly of TCC in the presence of a limited amount of C8beta or in the apparent absence of this subunit was confirmed using purified components, by mixing C5b6 and either of the purified C8 subunits together with C7 and C9. These data show that soluble TCC can be formed in C8beta-deficient sera that contain little or no C8beta.
From the serological screening for complement component deficiencies, we found 2 subjects with inherited C5 deficiency (C5D), 4 with C6D, 6 with C7D, 4 with C81 (alpha-gamma subunit) D and 138 with C9D among 145,640 healthy Japanese blood donors. Recently, the genetic bases of some of the C6D, C7D, C81D and C9D Japanese individuals were elucidated using an exon-specific PCR-SSCP method followed by direct sequencing of the target exons.
We have recently reported a French family presenting with an X-linked vacuolated myopathy. Here we show that levels of complement components C5 and C9 are elevated in the serum of these patients. Moreover, antitrypsin activity is decreased in the serum of the patients. Taken with the deposition of membrane attack complex encountered in muscle tissue, these results emphasize the role of complement in the pathogenesis of this rare muscular disorder.