Diversity of MICA (PERB11.1) and HLA haplotypes in Northeastern Thais

MICA or PERB11.1 is a polymorphic major histocompatibility complex (MHC) cl ass I-related gene located 46 kb centromeric of the HLA-B gene in the HLA c lass I region. It is expressed mainly in gut epithelial cells, keratinocyte s, endothelial cells, fibroblasts and monocytes, and is upregulated by heat stress. NUCA has been found to interact with gamma delta T cells, up CD8() and natural killer (NK) cells bearing the NKG2D/DAP10 receptor. The MICA gene displays a high degree of polymorphism with at least 54 alleles. In th e present study, polymorphic exons 2, 3 and 4 of the MICA gene were analyze d using sequencing based typing (SBT) in 255 unrelated healthy northeastern Thais. Thirteen previously reported MICA alleles were detected. MICA*008, *010, *002 and *019 Were highly predominant with the allele frequencies of 21.4%, 18.2%, 17.6% and 15.3%, respectively. Five of these 13 MICA alleles show significantly different frequencies from those of the Japanese and Cau casian populations. Interestingly, MICA052, which is a very rare allele in other populations, was prevalent with the allele frequency of 8.2%, mainly on the BLA haplotype carrying HLA-B*13 in this population. Strong linkage d isequilibria. were observed between MCA and HLA-B, as similarly observed in other populations, namely MICA*010-B*4601, MICA052-B*13, MICA*002-B*5801, and MICA*019-B*15 (1502, 1508, 1511, 1515, 1528, 1530). A large variety of three-locus (MICA - HLA-B - HLA-Cw) and six-locus (HLA-DQB1 - HLA-DRB1 - MI CA - HLA-B - HLA-Cw - HLA-A) haplotypes were recognized in the northeastern Thai population. This is the first report on MICA allelic distribution in Southeast Asian populations. These data will provide the important basis fo r future analyses on the potential role of the MICA gene in disease suscept ibility and transplantation matching in Southeast Asian populations.