HLA genes in Portugal inferred from sequence-based typing: in the crossroad between Europe and Africa.

The human leukocyte antigen-A (HLA-A), -B and -DRB1 polymorphism was examined in the Portuguese population, discriminating between North, Centre and South inhabitants. All data were obtained at high-resolution level, using sequence-based typing. The most frequent allele at each locus was A* 020101 (26%), B* 440301 and B* 510101 (12% each) and DRB1* 070101 (15%). The predominant three-locus haplotype was A*020101-B*440301-DRB1*070101 (3.1%), highly frequent in North Portugal (5.4%), lower in Centre (2%) and absent in the South. The present study demonstrates that the Portuguese population has been genetically influenced by Europeans and North Africans, via several historic immigrations. North Portugal seems to concentrate, probably due to the pressure of Arab expansion, an ancient genetic pool originated from several North Africans and Europeans, influences throughout millenniums. South Portugal shows a North African genetic influence, probably of recent origin by means of Berbers accompanying Arab expansion. We found that Centre Portugal is the distribution limit of some alleles and haplotypes that characterize the North or the South of the country. Despite North, Centre and South Portugal not being significantly different in allele frequencies, this study shows that HLA allele and haplotype frequencies are not homogeneous in the country. North and South Portugal show more similarity to North Africans in opposition to Centre which appears closer to Europeans.