Abstract:Molecular studies of HLA‐DRB, ‐DRA and ‐DQB1 genes in the variant DR2 haplotype, DR2LUM, were performed using the homozygous lymphoblastoid cell line, CTS. The results of HLA Class II gene RFLP and PCR analyses suggest that DR2LUM was created by a homologous recombination event between HLA‐DR1 and HLA‐DR15 haplotypes. Evidence for the presence of a recombinational “hotspot” in haplotypes possessing a DRB6 pseudogene is presented. The results of this study have important implications for detection of HLA‐DR2 alleles in DRB gene oligotyping strategies, and suggest that the CTS cell line will be a useful addition to cell panels for characterizi