The mechanism responsible for accommodation in renal transplantations across the blood barrier remains unclear. We recently encountered two patients with accommodated status after living-related kidney transplantations across the blood barrier. Both developed elevations of anti-blood-group antibodies to titers over 128x after transplantation, despite excellent renal function. We investigated the serum samples after the establishment of accommodation bound to the erythrocyte membrane of the donors or the third party with the same blood group. After the establishment of accommodation, the serum samples from both accommodated patients demonstrated a significant decrease in binding to the donors' erythrocyte membrane, but did not show any decrease in binding to the erythrocyte membrane of the third party. By contrast, serum samples from patients with graft loss after unsuccessful accommodation showed high anti-blood-type antibody activity directed towards both the donor's and the third party's erythrocytes. The result of this study suggests the difference of quality in antibodies produced by accommodated and nonaccommodated recipients.