Genotype frequencies of the human platelet antigen, Ca/Tu, in Japanese, determined by a PCR-RFLP method

Recently, the polymorphism of a new human platelet antigen, Ca/Tu, was shown to be derived from a G-A nucleotide substitution at base 1564 of GPIIIa cDNA, which leads to a single amino acid difference, Arg/Gln at amino acid 489 of GPIIIa. We developed a PCR-RFLP method to determine the genotypes of Ca/Tu and their frequencies in a Japanese population. Fifteen Ca/Tua donors comprising 1 Ca/Tu(a/a) homozygous donor and 14 Ca/Tu(a/b) heterozygous donors were found among the 314 random donors analyzed. The frequencies of Ca/Tu genes were 0.025 (Ca/Tua) and 0.975 (Ca/Tu(b)). The present study showed that the frequency of Ca/Tua individuals in the Japanese (15/314) was approximately 7-fold higher than in the Finnish population (1/150) previously reported by Kekomäki et al. Therefore, attention must be given to the involvement of the Ca/Tu alloantigen in neonatal alloimmune thrombocytopenia and the refractoriness of platelet transfusion.