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.