The MiIII phenotype among Chinese donors in Hong Kong: immunochemical and serological studies

The incidence of the MiIII phenotype among Chinese blood donors in Hong Kong was found to be 6.28%. Eleven individuals apparently homozygous for the MiIII gene were detected by immunoblotting with monoclonal antibodies R1.3 and R18. R1.3 detects an identical epitope on both glycophorins A and B and R18 detects a different epitope on glycophorin A. Immunoblotting with R1.3 showed an absence of bands corresponding to normal glycophorin B. Immunoblotting with R18 showed an absence of a 58 K band, which corresponds to a heterodimer of normal glycophorin B complexing with the MiIII component, found in MiIII heterozygotes. In two families with apparent MiIII homozygous individuals, both parents of the propositi had the MiIII phenotype which implies normal autosomal inheritance of the MiIII gene. In another family, only one parent had the MiIII phenotype and the presence of an Su gene is postulated to explain the immunochemical and serological findings.