摘要Background:Immunosuppressive agents are still inefficient in preventing biopsy-proven acute rejection (BPAR) after expanded criteria donor (ECD) kidney transplantation.The aim of this study was to investigate the relationships between early immunosuppressive exposure and the development of BPAR.Methods:We performed a retrospective study of 58 recipients of ECD kidney transplantation treated with enteric-coated-mycophenolate sodium,tacrolimus (Tac),and prednisone.The levels of mycophenolic acid-area under the curve (MPA-AUC)0-12h and Tac C0 were measured at the 1 st week and the 1st month posttransplant,respectively.The correlation was assessed by multivariate logistic regression.Results:The occurrence rates of BPAR and antibody-mediated rejection were 24.1％ and 10.3％,respectively.A low level of MPA-AUC0-12h at the 1st week posttransplant was found in BPAR recipients (38.42 ± 8.37 vs.50.64 ± 13.22,P ＜ 0.01).In addition,the incidence of BPAR was significantly high (P ＜ 0.05) when the MPA-AUC0-12h level was ＜30 mg·h-1·L-1 at the 1 st week (15.0％ vs.44.4％) or the Tac C0 was ＜4 ng/ml at the 1st month posttransplant (33.3％ vs.21.6％).Multivariable logistic regression analysis showed that the MPA-AUC0-12h at the 1s1 week (OR:0.842,95％ CI:0.784-0.903) and the Tac C0 at the 1 st month (OR:0.904,95％ CI:0.822-0.986) had significant inverse correlation with BPAR (P ＜ 0.05).Conclusions:Low-level exposure of MPA and Tac C0 in the early weeks posttransplant reflects an increased acute rejection risk,which suggested that MPA-AUCo-12h ＜30 mg·h-1·L-1 and Tac C0 ＜4 ng/ml should be avoided in the first few weeks after transplantation.