Allele frequencies (AFs) and haplotypic associations of human leukocyte antigen (HLA) class I and II were investigated in 400 unrelated, healthy, ethnic Northeast Thais. HLA-A, -B, -Cw, -DRB1 and -DQB1 were typed by polymerase chain reaction-sequence specific primer, -sequence specific oligonucleotide probe and -single-strand conformation polymorphism methods. In this population, 17 HLA-A, 26 HLA-B, 15 HLA-Cw, 26 HLA-DRB1 and 13 HLA-DQB1 alleles (or groups of alleles) were found. AFs > 10% included A*11 (23.3%), 24 (18.8%), 0207 (14.4%), 33 (11.5%), 0203 (10.6%); B*4601 (13.9%); Cw*07(01-03) (18.5%), 01 (15.9%), 04 (12.0%), 0304 (10.6%); DRB1*1502 (18.5%), 1202 (13.4%); DQB1*0502 (20.3%), 0501 (16.3%), 0301 (14.1%) and 02 (10.9%). The most common of 2-locus haplotypes included A*0207-B*4601 (9.3%), B*4601-Cw*01 (13.5%), B*5801-DRB1*0301 (5.8%) and DRB1*1502-DQB1*0501 (14.1%). Of the 49 five-locus HLA haplotypes identified, 24 were confirmed in 31 family studies: the most common being; A*33-Cw*0302-B*5801-DRB1*0301-DQB1*02 (4.6%), A*0207-Cw*01-B*4601-DRB1*09-DQB1*0303 (3.4%) and A*33-Cw*07(01-03)-B*44-DRB1*07-DQB1*02 (2.6%). Apparently, the HLA-B*46-carrying haplotype is fragmented in ethnic Northeast Thais, including seven haplotypes with different HLA-A and HLA-DR/DQ combinations. One of these haplotypes (A*11-Cw*01-B*4601-DRB1*1202-DQB1*0502) has not been reported in other Asians. The results indicated that there were marked differences in the distribution of HLA alleles and haplotypes between ethnic Northeast Thais and other ethnic groups in Southeast and East Asia. These results also dictate that future studies of HLA alleles and diseases need precise identification of ethnically and geographically matched controls. The HLA allele and haplotype analyses in this large sample provide baseline information on ethnic Northeast Thais for anthropological studies and for determining HLA allele/haplotype frequencies when searching for HLA-compatible donors for unrelated bone marrow transplantation.
This study demonstrates not only the differential association between HLA markers and types of psoriasis according to age at onset, but also a newly found high-risk and a protective haplotype in Thai psoriasis patients.
MICA or PERB11.1 is a polymorphic major histocompatibility complex (MHC) class I-related gene located 46 kb centromeric of the HLA-B gene in the HLA class I region. It is expressed mainly in gut epithelial cells, keratinocytes, endothelial cells, fibroblasts and monocytes, and is upregulated by heat stress. MICA has been found to interact with gamma delta T cells, alpha beta 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 the present study, polymorphic exons 2, 3 and 4 of the MICA gene were analyzed 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 Caucasian populations. Interestingly, MICA052, which is a very rare allele in other populations, was prevalent with the allele frequency of 8.2%, mainly on the HLA haplotype carrying HLA-B*13 in this population. Strong linkage disequilibria were observed between MICA 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 - MICA - 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 for future analyses on the potential role of the MICA gene in disease susceptibility and transplantation matching in Southeast Asian populations.
SummaryPolymorphic Alu insertions (POALINs) are known to contribute to the strong polymorphic nature of the Major Histocompatibility Complex (MHC). Previous population studies on MHC POALINs were limited to only Australian Caucasians and Japanese. Here, we report on the individual insertion frequency of the five POALINs within the MHC class I region, their HLA-A and -B associations, and the three and four locus alpha block POALIN haplotype frequencies in the Northeastern (NE) Thai population. Of the five POALINs, the lowest frequency was 0.018 for AluyHF and the highest frequency was 0.292 for AluyHJ and AluyHG. The strongest positive associations between the POALINs and HLA class I alleles was between AluyMICB and HLA-B * 57, AluyHJ and HLA-A * 24 and HLA-A * 01, and AluyHG and HLA-A * 02, supporting previous findings in Caucasians and Japanese. Single POALIN haplotypes were found more frequently than multiple POALIN haplotypes. However, of the seven different POALIN haplotypes within the MHC alpha block, there were only two significant differences between the NE Thais, Caucasians and Japanese. This study confirms that the MHC POALINs are in linkage disequilibrium with HLA-A and -B alleles and that there are significant frequency differences for some of the POALINs when compared between NE Thai, Caucasians and Japanese.
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