A comparison of molecular HLA-DR and DQ allele profiles forming DR51-, DR52-, and DR53-related haplotypes in five ethnic Thai populations from mainland southeast Asia.

Using PCR-SSOP typing we have deduced the composition and frequency of HLA-DRB1, -DRB3, -DRB4, -DRB5, -DQA1, and -DQB1 alleles present in DR51-, DR52-, and DR53-related haplotypes, in 519 individuals representative of five ethnic Thai populations recruited in central, northeastern and northern Thailand. In total, we have unequivocally detected at varying frequencies, 17 DR51-related haplotypes, 24 DR52 haplotypes, and 12 DR53 haplotypes in the study groups. We document evidence of north-south gradients of DR51-related haplotypes, whereby the overall frequency of DR51-containing haplotypes is relatively more common in the northern Thai groups. Similarly, within DR53-related haplotypes the frequency of DRB1*0901-containing haplotypes increases in the more northerly groups, and an inverse effect was observed with DRB1*0701-containing haplotypes that were relatively more common in the northeastern and central Thais. We have also compared the class II haplotype profiles of the Thais with the equivalent profiles reported in other non-Thai ethnic groups from mainland and insular SE Asia. One DR51-related haplotype DRB1*1502x, DRB5*0102x, DQA1*0101/4, DQB1*0501, would appear to be characteristic of Thai populations, as it was the most common DR2 haplotype in all five study groups and is also prevalent in other mainland southeast Asians, but is much less evident in the more northern populations of eastern Asia or China.

HLA class II allele frequencies in northern Thais (Kamphaeng Phet).

The polymorphism of HLA class II genes (HLA-DRB1, -DQA1, -DQB1 and -DPB1) was investigated in 97 normal Northern Thais (NT) from Kamphaeng Phet province using PCR-SSO typing. Allele frequencies (AF) have been determined. DRB1*1202 (17.5%), DRB1*1502 (16.5%), DQA1*0101 (25.8%), DQA1*0102 (21.7%), DQB1*0502 (22.7%), DPB1*0501 (23.2%) and DPB1*1301 (22.7%) showed the highest frequencies in each locus. These results were more similar to those observed in Present-day Thais (PDT) and Central Thais (CT) than Northern Thais from Chiang Mai (CM) and Dai Lue (DL). However, the data presented in this population study should be useful in many fields, such as anthropology, organ transplantation, disease susceptibility and evolutionary genetics.

HLA-DPB1 polymorphism in the Thais of Southeast Asia.

In this study we examined DPB1 allele frequencies in five ethnic Thai populations resident in different regions of Thailand and neighboring countries. In contrast to other Asian and Pacific populations such as the Japanese, Chinese, Korean, and Papua New Guineans, where DPB1*0501 has consistently been shown to be the most frequent allele, NE Thais and Thai-Khmers demonstrate a prevalence of DPB1*1301. Comparison of DPB1 allele frequencies in the Thais of SE Asia, with known frequencies in the Chinese and Japanese populations of E Asia, would appear to confirm previous calculations of genetic divergence between these Oriental populations.