To identify biomarkers of operational tolerance in pediatric and adult liver transplant recipients, transcriptional profiles were examined from 300 samples by microarrays and Q-PCR measurements of blood specimens from pediatric and adult liver transplant recipients and normal tissues. Tolerance-specific genes were validated in independent samples across two different transplant programs and validated by Q-PCR. A minimal set of 13 unique genes, highly expressed in natural killer cells (p = 0.03), were significantly expressed in both pediatric and adult liver tolerance, irrespective of different clinical and demographic confounders. The performance of this gene set by microarray in independent samples was 100% sensitivity and 83% specificity and the AUC was 0.988 for only three genes by Q-PCR. 26% of adults and 64% of children with excellent liver allograft function, on minimal or dual immunosuppression, showed high prediction scores for tolerance. Novel peripheral transcriptional profiles can be identified in operational tolerance in pediatric and adult recipients of liver allografts, suggesting a high incidence of a pro-tolerogenic phenotype in stable patients on chronic immunosuppression. Given the high incidence of viral infections and malignancies in liver transplant recipients, this gene set provides an important monitoring tool that can move the field toward personalized and predictive medicine in organ transplantation.

Tolerance has been defined as stable graft function off IMS. We reviewed the data of 369 pediatric liver transplant patients to examine demographic differences that may have a PV of pediatric LT tolerance. Of the 369 patients, 280 patients were stable with detectable blood levels of IMS agents and with good graft function without biopsy proven REJ > 1 yr posttransplantation, 18 patients were noted to be TOL off IMS, 27 patients were taking MIS with drug levels below detectable range by standard laboratory parameters, and 44 patients developed one or more episodes of biopsy proven acute or chronic REJ > 1 yr post-transplantation. Variables, including percentage of biliary atresia, type of transplanted organ, history of EBV infection, patient and donor gender, and ABO blood type mismatch between recipient and donor did not have PV of tolerance. Average age in years was 1.37 ± 1.53 (0.3-4.9) for TOL, 1.14 ± 0.89 (0.4-3.1) for MIS and 3.35 ± 4.45 (0.3-16) for REJ. Age difference of TOL/MIS vs. REJ was significant (p =0.002) and TOL vs. REJ was significant (0.01). Age at the time of transplantation is an important predictor in the development of pediatric LT tolerance.

Increased serum HLA-G levels track with operational tolerance of liver grafts and support favorable outcomes in pediatric and young adult recipients.

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