57–59 It is conceivable that, with a limited founder polymorphism, any novel allele that arose in these environments Vemurafenib purchase would enlarge the peptide-binding repertoire of these populations. Perhaps the HLA-B locus diverged more than the HLA-A or -DRB1 loci in the South American populations, as a result of a higher probability for intra-locus gene conversions because this locus presented a larger number of founder alleles. The informative value of HLA typing in anthropological investigations may be illustrated by our studies on Easter

Island (for more details, see refs 85–87). Although the available data suggest that Easter Island was first colonized by eastern-migrating Polynesians around 1000 years ago, there is also evidence of an early South American contact. As a matter of fact, the Norwegian

explorer Thor Heyerdahl proposed that Easter Island was first populated by American Indians (Amerindians). Previous studies of mtDNA or other chromosomal markers have, however, not been able to demonstrate an early Amerindian contribution to the gene pool on Easter Island or other Polynesian islands, before the Peruvian slave raids in Polynesia in the early 1860s, which resulted in an admixture of Amerindian and European genes in the area. To address this Palbociclib mw issue we carried out studies of DNA from blood samples collected in 1971 and 2008 from reputedly non-admixed native Easter Islanders. All typed individuals carried mtDNA of Polynesian origin, and most males carried Y-chromosome markers of Polynesian origin while the rest carried Y chromosome markers of European origin. Genomic typing of HLA demonstrated, however, that some individuals carried HLA alleles that are typically detected in Amerindians. For example, some individuals had an HLA haplotype PAK5 carrying A*02:12, B*39:05 and other alleles, which are not detected or are very rare in non-Amerindian populations (ref. 49; see also Table 4). We could trace the introduction of this haplotype on Easter Island to a time before the Peruvian slave raids. Our studies cannot establish exactly when these Amerindian alleles were introduced to Easter Island, but they indicate

that it may have occurred in ‘prehistoric’ times; i.e. before the island was discovered by Europeans in 1722, but after the island had been inhabited by Polynesians. There are at least two explanations why an early Amerindian contribution to the gene pool on Easter Island was not detected by studies of mtDNA and Y-chromosome markers. One is that the Amerindian HLA alleles may have been subject to different selective forces than Amerindian mtDNA and Y-chromosome markers, because the HLA genes encode molecules of great importance in immune responses. Another explanation is genetic drift. At the end of the 1800s approximately 100 individuals were left on the island as the result of the Peruvian slave raids and epidemics.