Within a few decades, liver transplantation has become an effective treatment of end-stage liver diseases associated with high spontaneous mortality. However, the consequences of immediate transplants are frequently complicated by infective (nosocomial infection) and immunological complications (acute graft rejection) in up to 40 to 60% of liver transplanted patients. In order to ensure graft immunotolerance, immunosuppressive therapy based mainly on calcineurin inhibitors, is initiated soon after liver transplantation. Immunosuppressive therapy is intended to reduce the response of cytotoxic lymphocytes and NK cells. As a result, an important component of the immune response is blocked. In addition, function of the transplanted liver, which is a key organ for both immuno-inflammatory signalling and host defense against pathogens, is progressively restored post-operatively. Thus in this post-transplant period, there is a critical period where liver function is severly impaired and progressively get restaured. The aim of this study is to characterize the restauration of immune function in the early post-operative period and evaluate its correlation with occurence of infective or immunological complications.