Incomplete Immune Tolerance in Pediatric ABO-Incompatible Liver Transplantation: Insights From Donor-Specific Antibody Titers

BACKGROUND Advancements in transplant immunology and pharmacotherapy have led to improved outcomes in pediatric ABO-incompatible liver transplantation. However, the long-term dynamics of donor-specific versus non-donor-specific blood group antibodies (BGAs) in this population remain unclear. This study aimed to determine whether incomplete immune tolerance to donor-specific BGAs persists after ABO-incompatible liver transplantation. MATERIAL AND METHODS This retrospective study included 29 pediatric patients who underwent ABO-incompatible living donor liver transplantation with extended follow-up. Five of these patients exhibited persistent donor-specific BGA titers greater than 1: 64 (IgG or IgM) and received standardized preoperative immunosuppression; all 29 patients received intraoperative and postoperative immunosuppression. Demographic data, pre- and post-transplant BGA titers, and histopathological findings from liver biopsies were collected and analyzed. RESULTS All recipients were blood type O; 10 received grafts from blood type A donors, whereas 19 received grafts from blood type B donors. Donor-specific BGA titers (both IgG and IgM) remained persistently low and were significantly lower than non-donor-specific BGAs (P<0.001). Liver biopsy findings revealed mild to moderate antibody-mediated rejection in 5 patients. All patients achieved long-term survival. CONCLUSIONS The persistently low titers of donor-specific BGAs in pediatric ABO-incompatible living donor liver transplantation recipients may indicate a state of incomplete immune tolerance, possibly influenced by the developmental characteristics of the pediatric immune system and preconditioning with monoclonal antibodies. Further studies are warranted to confirm these findings and clarify the mechanisms underlying immune tolerance in this setting.