IgM anti-recipient ABO antibodies predict acute graft-versus-host disease following allogeneic hematopoietic stem cell transplantation.

Passenger lymphocyte syndrome (PLS) presents as transient immune hemolysis due to anti-recipient ABO antibodies produced by donor B-lymphocytes accompanying minor or bidirectional ABO incompatible allogeneic hematopoietic stem cell transplantation (HSCT). We monitored both IgM and IgG type anti-recipient ABO antibodies in 18 consecutive HSCT recipients with hematological malignancies. Five of these patients (28%) developed transient immune hemolysis due to PLS after a median of 19 days post-HSCT. This response was associated with the detection of IgM and IgG anti-recipient ABO antibodies after a median of 16 and 22 days post-HSCT, respectively. All five patients subsequently developed acute graft-versus-host disease (GVHD) grades II-IV, and three died due to transplant-related mortality (TRM) within 1 year after HSCT, while in contrast, of the 13 patients without PLS, three (23%) developed grades II-IV acute GVHD (p < 0.01) and the 1-year TRM was 8% (p = 0.03). Thus, patients with PLS had a significantly lower 1-year overall survival than those without PLS (20 vs. 75%, p = 0.03). These findings suggest that the IgM anti-recipient ABO antibody may be an early predictor of acute GVHD and poor survival after minor or bidirectional ABO incompatible HSCT.