Serological studies of Cw1 and Cw3 expressed on the same haplotype

A serological comparison has been made between individuals who are phenotypically Cw1 and Cw3. The first individual is Oriental and carries Cw1 and Cw3 on the same haplotype, the other individuals are Caucasian and carry either Cw1, Cw3 or Cw1 and Cw3 on different haplotypes. No unique specificities could be found on the Oriental Cw1, Cw3 haplotype by reciprocal absorption experiments, inhibition of complement dependent microcytotoxicity by F(ab') 2 fragments prepared from Cw1 and Cw3 antisera or by lysostrip experiments. The blocking and lysostrip experiments also suggested molecular independence of Cw1 and Cw3 determinants coded for by Oriental Cw1 haplotype. The results suggest a recent gene duplication in Oriental populations or two loci in the C region.