Polymorphism of the fourth component of complement in Turks

An analysis of polymorphism in the fourth component of human complement (C4 ) was performed on EDTA-plasma from 142 unrelated, randomly selected Turks without collagen-vascular disease or recurrent infections, Plasma samples t reated with neuraminidase and carboxypeptidase-B were subjected to high-vol tage agarose gel electrophoresis followed by immunofixation. C4B allotypes were further detected in some samples by Western blots with monoclonal anti body 1228 (anti-C4B/Ch1 reactivity). The frequencies of C4A and C4B alleles were determined. Allele C4B*5, which has been found to be relatively commo n in Asian (Oriental) populations, was not detected in this study. No speci fic predilection could be noted among the rare variants. C4A*3-C4B*1 was th e most common haplotype (n = 40/142, or 28%) but was found less frequently than in Caucasian populations. This finding may be the result of the limite d number of samples examined. C4A and/or C4B null allotypes were seen in 49 of 142 (34.6%) subjects. The most frequent C4 null allotype seen was C4B n ull (37/142, or 26%): 28 subjects had one C4B null allele; 1 had a homozygo us deficiency of C4B (C4B*QO, *QO) and 7 had C4A*QO C4B*QO, a double hetero zygous haplotype. Frequencies of homozygous haplotype C4A*QO-C4B*QO in the population studied were found to be 0.007, The results of this study demons trate that the genetic composition of the Turkish population exhibits both similarities and differences with the European population, and ranges betwe en Caucasian and Mongoloid (Asian) populations.