Low Titers of Antidonor ABO Antibodies After ABO-Incompatible Living Donor Liver Transplantation: A Long-Term Follow-Up Study

BACKGROUND: The ABO blood-type barrier in kidney and liver transplantation has been overcome by aggressive treatments such as B cell depletion using rituximab. However, the long-term effects of ABO-incompatible liver transplantation (ABO-I LTx) on immunological status have not previously been studied. Here, we assessed whether long-term immune hyporesponsiveness against ABO blood-group antigens was retained. METHODS: We recruited 81 patients, 75 patients who had survived ABO-I LTx without retransplantation and 6 patients who had survived after retransplantation using blood type-compatible grafts. The time between ABO-I LTx and outpatient visits for blood sampling for this study ranged from 1.1 to 16.8 years. We also evaluated patients' backgrounds and postoperative therapies. RESULTS: Overall, antidonor ABO antibody titers in the 75 patients without retransplantation decreased during long-term follow-up. In the subset of 40 patients with blood type O, anti-nondonor ABO antibody titers did not decrease and were significantly higher than antidonor ABO antibody titers. In addition, long-term antidonor ABO antibody titers were significantly lower in pediatric patients than in adult patients. In the 6 patients who were retransplanted with blood type–compatible grafts, antidonor ABO antibody immunoglobulin G titers remained low, but IgM titers increased slightly long after removal of the ABO-incompatible graft. CONCLUSIONS: These findings suggest that donor-specific hyporesponsiveness remains after ABO-I LTx, particularly in pediatric patients. Long-term persistence of blood antigens may contribute to this donor-specific hyporesponsiveness.