['The T helper cell type 1 (Th1) cytokines interleukin (IL)-2 and interferon (IFN)-gamma are mediators of acute graft rejection after liver transplantation and Th2 cytokines, such as IL-4 and IL-10, may have a protective role and correlate with graft acceptance. To test the hypothesis that infants aged <1 year have an immunological advantage with regard to graft acceptance because of a partially immature immune system with a physiological balance toward a Th2 cytokine profile, we conducted the present study.', 'We compared the T helper serum cytokine profiles in 105 infants and children after liver transplantation with or without acute graft rejection and analyzed the normal age-distributed concentrations of T helper cytokines in 51 healthy controls.', 'The incidence of acute graft rejection was as follows: 0 to 12 months, 26.8%; 1 to 3 years, 40.0%; and >3 years, 71.8%. There was a significantly lower incidence of acute rejection in infants 0 to 12 months of age compared with children >1 year (11/41 vs. 38/64; P=0.001). In healthy infants, significant increasing Th1 cytokine concentrations and decreasing Th2 cytokine concentrations were found with increasing age. Patients with acute rejection had significantly higher values of Th1 cytokines compared with nonrejecting subjects, who had significantly higher concentrations of Th2 cytokines. A longitudinal analysis of serum cytokines from patients showed that changes of the cytokine patterns in the follow-up did not differ significantly from preoperative values, except in the 4 weeks posttransplant.'] Does th2 cytokine profile in infants predispose to improved graft acceptance after liver transplantation?