Genotype of the human leukocyte antigen (HLA)-DQA1 locus was analyzed in Koreans (n= 467) using the 14th International Workshop protocol established to characterize the sequences of exons 1-4 of the gene. Unexpectedly, it appeared that the DQA1 (19 alleles) was more diverse than DQB1 (15 alleles) in the study population. DQA1*010201, DQA1*0303, DQA1*0103, and DQA1*0302 appeared to be major alleles exhibiting more than 10%. Among six allele groups, DQA1*01-*06, DQA1*01 showed highest diversity exhibiting seven different alleles. Analysis using maximum likelihood method showed numerous multi-locus HLA haplotypes. High relative linkage disequilibrium values (RLD) of the two-locus haplotypes and exclusive association of a specific DQA1 allele with a specific DRB1 and/or DQB1 alleles suggested tight linkage of DQA1 to DRB1 and DQB1. In HLA-matching process for hematopoietic stem cell transplantation, however, DQA1 typing would be informative for individuals carrying specific DRB1 allele (DRB1*0802, DRB1*1201, or DRB1*1403) that could be associated with multiple DQA1 alleles in the study population. Information obtained in this study will be useful in medical and forensic areas as well as in anthropology.

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Four novel human leukocyte antigen (HLA)-DQA1 alleles have been characterized by direct DNA sequencing of coding exons 1-4. All the novel alleles exhibited a single nucleotide substitution either in exon 3 or in exon 4 when compared with previously defined alleles. Thus, it is likely that alleles were generated by point mutation from pre-existing alleles in the population. Substitutions resulted in either a silent (DQA1*010203) or an amino acid change (DQA1*0506, DQA1*0507, and DQA1*0508). The substituted sites were both previously known polymorphic and conserved positions. Putative haplotypes associated with the novel alleles were deduced based on the HLA types shared by the individuals carrying a novel allele or from previously reported population data.