Incidence of disease progression by HLA- DPB1 matching and disease risk by DRI. There was no statistically significant difference regarding the risk for disease progression among donor-recipient pairs by HLA-DPB1 mismatching (A). The cumulative incidences at 3 years were 26%, 29%, and 34% for mismatched nonpermissive GVH, mismatched nonpermissive HVG, and mismatched permissive pairs, but the incidence was 41% for HLA-DPB1–matched pairs. However, there was a significant interaction between HLA-DPB1 mismatches and disease risk groups by DRI (B). Lower risk for disease progression was observed with any HLA-DPB1 mismatch in the intermediate-risk group by DRI but not others. Intermediate-risk patients by DRI with any HLA-DPB1 mismatch had a lower risk for disease progression with an incidence of 25%, which was similar to 19% observed in patients with low-risk DRI. However, intermediate-risk patients without any HLA-DPB1 mismatch had an increased risk for progression with an incidence of 41%, which was similar to 46% observed in patients with high/very high-risk DRI.