In ABO-incompatible live renal transplantation (ABOI-RTx), anti-blood type A/B antibody (anti-A/B Ab) depletion is performed before transplantation to avoid humoral rejection caused by anti-A/B Ab. In a quite rare case, so severe a hyperacute rejection occurs in ABOI-RTx as to result in graft loss, regardless of titer of anti-A/B Ab.We newly developed a flow cytometry-based detection method of anti-blood type A/B IgG antibody (anti-A/B IgG Ab) that has complement-binding affinity using human complement C1q to elucidate immunological mechanism of humoral rejection caused by anti-A/B Ab in ABOI-RTx. This method revealed that positivity rate of C1q-binding affinity in anti-A/B IgG Ab was higher in patients of ABOI-RTx whose graft function was lost, while that rate was lower in those with stable renal function.We, therefore, suggest that this method might have a possibility to become a useful test in ABOI-RTx to avoid humoral rejection.
