BACKGROUNDAcute rejection remains an important cause of renal allograft dysfunction and the need for accurate diagnosis is essential to successfully treat transplant recipients. The purpose of this study was to determine the costimulatory molecules OX40 and OX40L messenger RNA (mRNA) levels in peripheral blood mononuclear cells (PBMCs) to predict acute renal transplant rejection.

METHODSThe whole blood samples from 20 recipients with biopsy-confirmed acute rejection (rejection group), 20 recipients with stable graft function and normal biopsy results (stable group) after kidney transplantation, and 20 healthy volunteers (control group) were collected. The mRNA levels of OX40 and OX40L were analyzed with TaqMan real-time reverse transcriptase polymerase chain reaction (RT-PCR). The association of OX40 and OX40L mRNA levels with disease severity was investigated.

RESULTSThere was no significant difference of OX40, OX40L mRNA levels in PBMCs between the stable group and control group (P > 0.05). The levels of OX40 and OX40L mRNA were significantly higher in the rejection group than in the control group (P < 0.01 and P < 0.05, respectively). Non-significantly higher OX40L mRNA and significantly higher OX40 mRNA in PBMCs were observed in subjects in the rejection group compared with the stable group (P > 0.05 and P < 0.01, respectively). Receiver operating characteristic (ROC) curve analysis demonstrated that OX40 mRNA levels could discriminate recipients who subsequently suffered acute allograft rejection (area under the curve, 0.908). OX40 and OX40L mRNA levels did not significantly correlate with serum creatinine levels in the rejection group (P > 0.05). Levels of OX40 mRNA after anti-rejection therapy were lower than those at the time of protocol biopsy in the rejection group (P < 0.05).

CONCLUSIONOur data suggest that measurement of OX40 mRNA levels after transplant might offer a noninvasive means for recognizing recipients at risk of acute renal allograft rejection.