Wang HY, Cui Z, Pei ZY, et al. - In view of a genome-wide association study indicating an association between myeloperoxidase-ANCA associated vasculitis (AAV) and HLA-DQ, researchers sought for susceptibility alleles in these loci. Genotyping of 258 Chinese patients with myeloperoxidase-AAV and 597 healthy control individuals at HLA DRB1, DQA1, DQB1, and DPB1 was performed and the encoded amino acid sequences were extracted from the IMGT/HLA database. Ninety-seven cases were included in the replication cohort and controls were comprised of 107 individuals. Risk alleles for myeloperoxidase-AAV were DQA1∗0302 (odds ratio 2.34) and DQB1∗0303 (odds ratio 1.89). In overt linkage disequilibrium (r² 0.69), these alleles were present and in addition, a significant risk was evident with the haplotype DQA1∗0302-DQB1∗0303 (haplotype score 6.39). Significant risk for myeloperoxidase-AAV was observed in correlation with aspartate160 on the DQ α chain (odds ratio 2.06 (1.60-2.67)), encoded by DQA1∗0302, and isoleucine185 on the DQ β chain (odds ratio 1.73 (1.38-2.18)), encoded by DQB1∗0303, both located in the α2β2 domains. Homologous modeling suggests that via altering dimerization of the HLA molecules, DQα∗160D may confer susceptibility to myeloperoxidase-AAV. Thus, they recommend paying more attention to the roles of amino acids in the α2β2 domains in addition to the α1β1 binding groove of HLA class II molecules.