Comparison of HLA class I gene sequences. Derivation of locus-specific oligonucleotide probes specific for HLA-A, HLA-B, and HLA-C genes.

The major histocompatibility complex in man contains at least 20 class I genes. Included within this family are three closely linked loci with 11-47 codominant alleles that encode the classical transplantation antigens HLA-A, -B, and -C. The study of individual HLA-A, -B, and -C genes is complicated both by the high degree of sequence homology among all members of the class I gene family and by the high degree of polymorphism exhibited by HLA-A, -B, and -C genes. Identification of potential locus-specific regions suitable for use as unique probes has been limited by the small number of nucleotide sequences available for comparison. In the present study, the nucleotide sequences of two cDNA clones, designated HLA-4 and HLA-10, that encode previously unsequenced alleles of HLA-C and HLA-A genes, respectively, are compared with those of other class I genes. From these intergenic and interallelic comparisons, it was deduced that the nucleotide sequence encoding amino acids 291-299 of the transmembrane region showed sufficient divergence between loci and similarity between alleles, to be suitable for the generation of locus-specific probes. Synthetic oligonucleotides were generated and shown to be highly locus-specific in hybridization. These probes were used successfully for the quantitation of the relative amounts of mRNA transcribed in human liver from HLA-A, -B, and -C genes; they should greatly simplify future studies of restriction fragment length polymorphisms of HLA-A, -B, and -C alleles as genetic markers of disease susceptibility.