Vitamin D and the risk of acute allograft rejection following human liver transplantation

Background: Vitamin D may act as an immune modulator in experimental and human organ transplantation, but these data are yet to be confirmed in human liver transplantation (LT). Aim: This study aimed to assess the relationship between acute liver allograft cellular rejection (ACR) and pretransplant serum vitamin D concentration or post-transplant vitamin D supplementation. Method: We studied 133 LT recipients who underwent two per protocol allograft biopsies in the early post-operative period, plus on-demand biopsies as clinically indicated. ACR estimate was given according to the Banff scheme in biopsies obtained along two follow-up periods: (a) from the transplant operation to the end of the second month (0-2 months); (b) and from the third month to the end of the eighth month (3-8 months) post-LT. Results: The median pretransplant serum 25-hydroxyvitamin D concentration was 12.5 ng/ml; 40 patients had concentrations ≤12.5 ng/ml, of whom six had ≤5.0 ng/ml. Seventy-nine recipients received oral vitamin D₃ supplementation to treat post-transplant osteoporosis. In the 0-2 months period, moderate-to-severe rejection episodes were independently associated with cytomegalovirus reactivation (P<0.005) and progressively lower pretransplant serum 25-hydroxyvitamin D concentrations (P<0.02). Early vitamin D₃ supplementation was independently associated with a lack of ACR (P<0.05). Conclusions: These results suggest that vitamin D may favour immune tolerance towards the liver allograft.