Abstract
Recent progress in the molecular biology of human major histocompatibility complex class II genes (HLA-DP, -DQ, -DR) have shown that the genetic complexity and allelic polymorphism are greater than expected. In the case of HLA-DR, three DR beta-chain loci have been identified and linked, two of which (DR beta I and DR beta III, now assigned names HLA-DRIB and HLA-DR3B) are functional. We have shown that the HLA micropolymorphism detected at the DNA sequence level can easily be analyzed by hybridization with allele-specific oligonucleotides (HLA "oligotyping"). In the case of the HLA DRw52 supertypic specificity, which includes the DR3, DR5, DRw6, and DRw8 haplotypes, three alleles, referred to as DRw52a, DRw52b, and DRw52c, have recently been identified at the HLA-DR3B locus by DNA sequencing. Hybridization with locus- and allele-specific oligonucleotide probes (designated 52a, 52b, and 52c) has been performed on DNA from normal individuals forming a panel of 82 haplotypes to establish the distribution of these three alleles. Individuals of the DR3 haplotype had either the DRw52a or DRw52b allele, and individuals of extended haplotype HLA-A1,B8,DR3 had only the DRw52a allele. DR5 individuals all had the DRw52b allele, while individuals of DRw6 haplotype had the DRw52a, -52b, or -52c allele. None of these three alelles are found in DRw8 individuals. Analysis of this micropolymorphism, undetectable by common typing procedures, is therefore now operational for more accurate HLA matching for transplantation and for improving correlations between HLA and disease susceptibility.