The eighth component of human complement (C8) is a serum protein consisting of three chains (α, β, and γ) and encoded by three different genes, C8A, C8B, and C8G. C8A and C8B are closely linked on chromosome 1p, whereas C8G is located on chromosome 9q. In the serum the β subunit is non-covalently bound to the disulfide-linked α-γ subunit. Patients with C8β deficiency suffer from recurrent neisserial infections such as meningitis. Exon-specific polymerase chain reaction (PCR) amplification with primer pairs from the flanking intron sequences was used to amplify all 12 C8B exons separately. No difference regarding the exon sizes was observed in a C8β-deficient patient compared with a normal person. Therefore, direct sequence analysis of all exon-specific PCR products from normal and C8β-deficient individuals was carried out. As a cause for C8β deficiency, we found a single C-T exchange in exon 9 leading to a stop codon. An allele-specific PCR system was designed to detect the normal and the deficiency allele simultaneously. Using this approach as well as PCR typing of the Taql polymorphism located in intron 11, five families with 7 C8β-deficient members were investigated. The mutation was not found to be restricted to one of the two Taql RFLP alleles. The mutant allele was observed in all families investigated and can therefore be regarded as a major cause of C8β deficiency in the Caucasian population. In addition, two C8β-deficient patients were found to be heterozygous for the C-T exchange. The molecular basis of the alleles without this point mutation also causing deficiency has not yet been defined.
|Number of pages||5|
|Journal||Journal of Immunology|
|Publication status||Published - Jun 1 1993|
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