C6 phenotyping in sera and bloodstains by isoelectric focusing followed by electroimmunoblotting.

The genetic polymorphism of C6 was investigated in 329 unrelated Japanese individuals using isoelectric focusing in polyacrylamide gels followed by an electroimmunoblotting technique. Besides six common phenotypes C6 A, AB, B, AB2, BB2 and B2, six rare variants were observed. The allele frequencies were: C6A = 0.4422, C6B = 0.4757, C6B2 = 0.0714, C6A3 = 0.0015, C6M1 = 0.0046 and C6B3 = 0.0046. The population data confirmed that the C6*B2 allele is the third common allele characterizing Japanese. The present electroimmunoblotting technique was applied to demonstrate C6 types in dried bloodstains. The C6 types were determined from bloodstains stored at 4 degrees C for up to 10 weeks, at room temperature for up to 2 weeks and at 37 degrees C for up to 4 days. The results show that this component system offers a new powerful means for the medico-legal grouping of bloodstains.