Risk factors for liver rejection: evidence to suggest enhanced allograft tolerance in infancy

After liver transplantation, a relatively low intensity immunosuppressive regimen is employed in our unit: after initial triple therapy (prednisolone, azathioprine, cyclosporin), prednisolone is discontinued at three months and azathioprine at one year. A retrospective study was therefore performed to determine the incidence of rejection, and to identify risk factors for rejection in our patient population. Over a 10 year period, 135 transplants were performed on 109 children. Thirty four (25%) were on infants less than 1 year old. Incidences of acute rejection and irreversible chronic rejection were calculated for grafts surviving more than one and four weeks respectively. Acute rejection occurred in 51 of 101 allografts (50%), and irreversible chronic rejection in 11 of 91 allografts (12%). The immunosuppression strategy was not associated with an increased incidence of rejection. Acute rejection occurred in only eight of 28 allografts (29%) in those transplanted during their first year, compared with 43 of 73 (59%) in older children. Logistic and Cox regression analysis supported age at transplantation as a significant risk factor for acute rejection. Irreversible chronic rejection did not occur in any of 24 grafts in patients transplanted before one year, compared with 11 of 67 (16%) in older recipients. This suggests possible enhanced allograft tolerance with transplantation during the first year of life. This unexpected and potentially important finding now requires confirmation in other large patient series, with blind interpretation of post-transplant liver biopsies.