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Background: Initial interruption of immunosuppression for 72 hr was analyzed in renal transplant recipients according to Calne et al.'s "window of opportunity for immunologic engagement" (WOFIE) concept., Methods: This pilot study was designed as a randomized, open-label, prospective trial of 40 recipients (20 in the WOFIE group, 20 in the control group) of cadaveric kidney transplants who were followed up for 2 years. Immunosuppression comprised tacrolimus (trough levels 5-8 ng/mL), daclizumab (1 mg per kilogram of body weight on day 0 and after 2, 4, 6, and 8 weeks), mycophenolate mofetil (1-2 g/day), and prednisolone (maintenance dose of 10 mg/day). After induction with daclizumab, prednisolone, and mycophenolate mofetil, immunosuppression was interrupted for 72 hr in the WOFIE group. Steroid withdrawal followed in both groups within 12 to 16 weeks posttransplant., Results: Patient and graft survival did not differ significantly between the two cohorts. However, the WOFIE group experienced less acute rejection episodes and developed better graft function. Although all but one of the patients in the WOFIE group successfully discontinued steroid treatment, permanent steroid withdrawal was achieved in only 76.4% of the control group. After daclizumab discontinuation, the WOFIE group demonstrated an increase of CD4CD25 T cells in peripheral blood (P<0.05 vs. control group), which was stable over time and strongly correlated with a significantly higher expression level of Foxp3-mRNA., Conclusions: Initial interruption of immunosuppression for 72 hr correlates with the induction of regulatory immunologic mechanisms and allows early and reliable minimization of immunosuppressive treatment.

Background: According to the window of opportunity for immunologic engagement (WOFIE) concept, as designed by R. Calne, the authors prospectively analyzed the effect of a 72-hr immunosuppressive window on graft function in renal transplant recipients., Methods: Immunosuppressive therapy comprised tacrolimus (trough levels, 5-8 ng/mL after day 8 posttransplantation), daclizumab (1 mg/kg body weight at day 0 and 2, 4, 6, and 8 weeks posttransplantation), mycophenolate mofetil (MMF) (1-2 g/day), and prednisolone. All patients received an induction therapy including daclizumab, prednisolone, and MMF. WOFIE patients were stopped from immunosuppression for 72 hr posttransplant. Steroids were withdrawn in both groups 12 to 16 weeks after transplantation and dual therapy with MMF and low-dose tacrolimus ensued., Results: Thirty renal transplant recipients (16 in the WOFIE group and 14 in the control group) have been enrolled since May 2000. Patient and graft survival were 93.8% and 87.5%, respectively, in the WOFIE group and 100.0% and 92.9% in the control group, respectively. One patient in the WOFIE group died of cytomegalovirus infection with stable graft function. There were no grafts lost because of acute rejection or primary nonfunction in either group. Patients treated according to the WOFIE protocol revealed less acute rejection episodes during the time of observation (first biopsy-confirmed acute rejection rate 12.5% in the WOFIE group vs. 42.9% in the control cohort). Whereas 92.1% of the WOFIE patients were successfully discontinued from steroids, permanent steroid withdrawal was achieved in only 60% of the control cohort., Conclusions: Initial interruption of immunosuppression was associated with a decrease of acute graft rejections. Subsequently, the authors postulate a synergistic effect on the immunosuppressive efficiency of calcineurin inhibitors when combined with an initial drug-free window.