Full-length cDNA nucleotide sequence of a serologically undetectable HLA-DQA1 allele: HLA-DQA1*"LA"

This study describes the characterization of a serological HLA-DQ"blank" specificity that segregates with the HLA-A2, -B7, -DR14, -DR52 haplotype. Although conventional serological typing techniques could not detect an HLA-DQ product on the haplotype positive for the HLA-DQ"blank" specificity, sequence-specific oligonucleotide (SSO) dot-blot analysis demonstrated the presence of the HLA-DQA1*01 and HLA-DQB1*05 alleles. Full-length cDNA nucleotide sequence analysis revealed that the HLA-DQB1 allele that segregated with the HLA-DQ"blank" specificity was identical to HLA-DQB1*05031. As for the HLA DQA1 allele, one nucleotide substitution distinguished the HLA-DQA1 "blank" allele from HLA-DQA1*0104. In exon 2 at nucleotide position 304 a C was substituted for a T (Arg-->Cys). Pending official recognition by the WHO Nomenclature Committee, this HLA-DQA1 "blank" allele is termed HLA-DQA1*"LA". Furthermore, it is postulated that the introduction of cysteine at amino acid position 102 abrogates the classical HLA-DQ1 specificity.