The plasma FK506-binding protein 12 level is related to acute cellular rejection in small bowel transplantation

Since FK506 binding protein (FKBP12) inhibits dose-dependently the immunosuppressive activity of FK506 in vitro, plasma FKBP12 levels were measured after rat small bowel transplantation (SBTx). The mean plasma FKBP12 level in untreated recipients increased significantly at the onset of acute cellular rejection (ACR) compared to that in FK506-treated recipients without rejection at the same time after SBTx (P < 0.05). In both groups, however, the mean plasma FKBP12 level did not increase at 1 day after SBTx. These results suggest that plasma FKBP levels may be affected by ACR, but not by ischemia-reperfusion injury. Therefore, the plasma FKBP12 level should be considered as one of the parameters related to the immunosuppressive activity of FK506 in SBTx.