Characterization of DR blank alleles by restriction fragment length polymorphism (RFLP)

Using a combination of conventional DR serology and RFLP analysis of DR beta and DQ beta, we have been able to identify two different types of DR antigens which belong so far to the DR blank group. The antigen DR-LOT is found on a haplotype A29, Bw60, Cw3, DRblank, DRw52, DQw1. The DR beta-EcoRI RFLP pattern of this haplotype is different from the patterns observed for DR1, DR2, DR3, DR4, DR5, DRw6, DR7, DRw8, DRw9, DRw10, and appears to be composed of a combination of DR2 and DRw6. The DQ beta-EcoRI pattern shows that this haplotype carries the DQw1 split DQR2.6. The second DR blank antigen which we found in a total of five individuals (three unrelated persons and two parents) on B35 positive haplotypes is characterized by a DR beta-EcoRI RFLP pattern indistinguishable from DR1 and by negative reaction with anti-DR1 sera. This antigen appears to be identical to what has been described by Cambon-Thomsen et al. (1986) and Bidwell et al. (1985) as HLA-DR-BON and DR"BR" respectively. We have demonstrated that this antigen is in strong linkage disequilibrium with the DQw1 split DQR1.