Platelet alloantigen frequencies in Amazon Indians and Brazilian blood donors

The frequencies of human platelet-specific alloantigens (HPAs) vary between different ethnic groups, and genotyping using DNA techniques has been pref erred over immunophenotyping methods for population studies. Using a polyme rase chain reaction with allele-specific primers (PCR-ASP) method, we deter mined the allelic polymorphisms of five HPA systems among 174 unrelated ind ividuals of two different Brazilian ethnic groups including Amazon Indians (n = 95) and blood donors (n = 79). Comparison of the calculated gene frequ encies of the two alleles of HPA-1, -2, -3, -4 and -5 systems for Amazon In dians and Brazilian blood donors showed that gene frequencies obtained for the two alleles of HPA-1 (P < 0.001), HPA-2 (P = 0.001) and HPA-5 (P < 0.00 1) were significantly different between the two groups of individuals. All natives tested carried the HPA-2a and the HPA-5a alleles, but the HPA-1b an d HPA-4b alleles are absent from the Indian population. It was also observe d that all blood donors carried the HPA-1a, HPA-4a and HPA-5a alleles. In c onclusion, the present data indicate differences in the frequency of the HP A systems between Amazon Indians and Brazilian subjects who present a high rate of racial admixture. While the frequencies of the HPA-1 and HPA-5 gene s seen in Amazon Indians are similar to those reported for Oriental populat ions, the frequencies of the HPAs alleles in Brazilian blood donors are com parable to those reported for populations in North America and Europe.