HLA class II allelic variation and susceptibility to pemphigus vulgaris

The autoimmune dermatologic disease pemphigus vulgaris (PV) is associated with the HLA serotypes DR4 and DRw6. Susceptibility to PV could be conferred either by sequences shared between the DR4 and DRw6 haplotypes or by different sequences in these haplotypes. We have examined the distribution of DR and DQ β-chain and DQ α-chain alleles in PV patients and in control subjects by hybridization with oligonucleotide probes and sequence analysis of in vitro amplified DNA. Ninety percent (34/38) of the DR4 haplotypes in patients contain a specific DRβI sequence present in 36% (16 of 44) of DR4 controls (P = 0.001). This sequence is also found in DRw6 haplotypes. However, it is present in only 25% (6 of 24) of DRw6 patients. The results of our analysis indicate that predisposition to PV is conferred by different sequences in DR4 and DRw6 haplotypes. The DR4 susceptibility is highly associated with the Dw10 DRβI allele, implicating the polymorphic residues in the third hypervariable region. The DRw6 susceptibility is strongly associated with a rare DQβ allele (DQB1.3). This allele differs from a common DQβ allele (DQB1.1) only by a valine→aspartic acid substitution at position 57.