Higher Sensitivity of Peripheral Blood Lymphocytes to Endogenous Glucocorticoid in Renal Transplant Recipients Treated with Tacrolimus, as Compared to those Treated with Cyclosporine

: Lymphocyte sensitivity to endogenous glucocorticoid cortisol could be a biological marker for safe reduction and withdrawal of steroids in renal transplant recipients. We compared peripheral lymphocyte sensitivity with cortisol between transplant recipients treated with tacrolimus (Tac) and those treated with cyclosporine. The suppressive efficacies of cortisol against T-cell mitogen-stimulated proliferation of peripheral lymphocytes were investigated in 44 renal transplant patients, who either had reduced or been withdrawn from steroid treatment. Twenty of the 44 patients were treated with Tac, and the other 24 patients were treated with cyclosporine A (CyA). The lymphocyte sensitivity to cortisol was compared between these two patient groups. The cortisol IC50 values in the Tac and CyA groups were 0.09 ± 0.12 and 14.2 ± 12.7 ng/ml, respectively. Lymphocyte sensitivity to cortisol in the Tac-treated group was significantly higher than that in the CyA-treated group (p = 0.0283). On the other hand, incidences of steroid withdrawal syndrome and increases in serum creatinine concentration were not significantly different between the Tac and CyA groups. Lymphocyte sensitivity to cortisol was higher in the Tac-treated patients than that in the CyA-treated ones. Since the cortisol sensitivity of peripheral lymphocytes is suggested to be a predictive marker for safe steroid withdrawal, Tac administration shows promise in aiding successful withdrawal of steroid treatment in long-term renal transplant recipients.