HLA-DRB1 and type 1 diabetes mellitus: Furthermore, inhibitory effects of cluster 5 substitutions on JM antibody binding were associated with HLA-DQB1*0302 expression within HLA-DRB1*04 patients, suggesting that this major type 1 diabetes susceptibility allele may influence the specificity of the IA-2 autoimmune response, in particular to the JM region that may dominate around the time of first appearance of IA-2 autoimmunity.