The genetics of the sixth and seventh complement components in man

York, Laura Jean (1981) The genetics of the sixth and seventh complement components in man. Masters thesis, Memorial University of Newfoundland.

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Abstract

The purpose of this thesis was to study the human complement components C6 and C7, in Newfoundland and to pursue the genetics of these proteins within the limits of the material obtained and the time allowed. -- Approximately 2400 sera from three Newfoundland populations were allotyped by the method of isoelectric focusing in polyacrylamide gel followed by specific hemolytic overlay. The frequencies of the common alleles were calculated for two of these populations. The West Coast community had frequencies of C6*a (0.6321) and C6*B (0.3670) and the Newfoundland families plus random individuals in a group had C6*A (0.6947) and C6*B (0.2980. These frequencies are similar to those found in other populations. The C6 alleles observed in the three populations were inherited in a manner consistent with a single autosomal locus and there was no evidence to suggest selection against the inheritance of the rare alleles. Examination for linkage of C6 with HLA reiterated the negative results of previous studies. An attempt to link the C6 and SOD (superoxide dismutase) loci in a West Coast family having a rare SOD variant was made but the data were uninformative. -- The homozygous C7*1 pattern was by far the most commonly observed, occurring in more than 99% of the samples allotyped. The novel observation and investigation of an artifact associated with prolonged serum storage of the C7*1 protein such that it is modified and mimics the migration of the C7*3 protein during isoelectric focusing is described. Genuine C7*3 alleles were also observed, two in heterozygote form, C7 3-1, and one which was due to either C7*3 homozygosity or C7 3-0. Data suggesting the C7*2 allele is of Chinese origin are presented. -- ADDENDUM -- Since the final writing of this thesis, nine unrelated local Chinese people have been bled and their serum typed for C7. Of the nine, three were heterozygous for C7*2. This supports the suggestion that this allele is of Chinese origin and appears with a frequency of approximately 17%. Further studies are currently in progress to accumulate family data for linkage efforts. -- SECOND ADDENDUM -- Following evaluation of this thesis, it has been pointed out that the term “allele” has been used here, as it sometimes is in published literature on C6 & C7, in an imprecise manner. The DNA sequence coding for a polymorphic polypeptide is, strictly speaking the allele, whilst the polymorphic poly-peptide or protein should be referred to as the gene product. The thesis should be read with this reservation in mind.

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