Impact of ABO Imcompatibility On Acute GvHD and Thrombotic Microangiopathy After Reduced-Intensity Cord Blood Transplantation.

Althouth ABO blood type is one of two antigen system for transplantation, the effect of ABO incompatibility on transplantation outcome still remains controversy. Furthermore, there is little data about ABO incompatibility on the outcome of unrelated cord blood transplantation following reduced-intensity conditioning (RI-CBT).

We retrospectively analyzed data of 155 patients who underwent RI-CBT performed at Toranomon Hospital from January 2005 to December 2008. The patients include 45 ABO-identical, 47 minor, 43 major, and 20 bidirectional ABO mismatched. All patients were performed using fludarabine-based reduced-intensity conditioning, and 114 patients (74%) were performed using TBI-containing regimen. Median age were 57 years-old and 94 patients (61%) were over 55 years-old. We evaluated the association between ABO incompatibility and neutrophil engraftment, one-year overall survival (OS) ; one-year non-relapsed mortality (NRM) ; and one-year relapse rate. We also analyzed the incidence of pre-engraftment immune reaction (PIR), acute graft-versus-host disease (GvHD) including severity, and thrombotic microangiopathy (TMA).

There were no significant differences in neutrophil-engraftment time, reticulocyte-engraftment time, and the incidence of PIR. The incidence of acute GvHD and grade 2-4 acute GvHD were significantly higher in major/bidirectional ABO-incompatible group than ABO-identical/minor ABO-incompatible group (respectively P=0.0008 and P=0.0116). The incidence of TMA tended to be higher in minor/bidirectional ABO-incompatible group than ABO-identical/major ABO-incompatible group (P=0.0637). There were no significant differences in one-year OS, NRM, and relapse rate. In multivariate analysis, risk factors of acute GvHD were age over 55, TBI-containing regimen, CD34-positive cells>0.7×10e5/kg, and major/bi-directional ABO incompatibility, and those of TMA were grade 3-4 acute GvHD and minor/bi-directional ABO incompatibility.

This study showed major-directional ABO incompatibility setting increased the incidence of acute GvHD. Sex incompatibility and HLA incompatibility were not significantly influenced the incidence of acute GvHD. The use of steroid for severe GvHD and the expression of ABO antigen on the surface of vascular endothelial cell may influence pathogenesis of TMA. Further studies including larger patients numbers are required to elucidate the impact of ABO incompatibility on the clinical outcome of RI-CBT.

No relevant conflicts of interest to declare.