Anti-host isohemagglutinin production is associated with a higher risk of acute GVHD in ABO-incompatible transplantation.

We retrospectively analyzed the association between anti-host isohemagglutinin (IH) production and the development of acute GVHD. Of 189 patients who received minor or major/minor ABO-incompatible hematopoietic SCT (HSCT) at our hospital, 36 patients (19%) showed IH production. IH was detected before the onset of acute GVHD in 10, around the same time in 8, and after the onset of acute GVHD in 17 patients. The cumulative incidence of grade II-IV acute GVHD was significantly higher in the IH+ group compared with the IH- group (P<0.0001). The higher risk of acute GVHD that was associated with IH production occurred irrespective of human leukocyte Ag compatibility and donor type. Furthermore, the incidence of acute GVHD in the IH- group was comparable to that seen in major ABO-incompatible or -compatible HSCT. Our findings not only showed a strong association between IH production and acute GVHD development, but also suggested that IH production might be a useful predictor of subsequent acute GVHD after ABO-incompatible HSCT.