Impaired prednisolone sensitivities of the endocrine system and peripheral-blood lymphocytes are closely related to clinical incidence in renal transplantation.

Endocrine- and immune-responses to prednisolone and their relation to clinical incidence were assessed in 19 renal transplant recipients. All of the patients were treated with prednisolone and cyclosporin. Response of the hypothalamic-pituitary-adrenal (HPA) system to prednisolone was evaluated by measuring serum cortisol concentration. Cortisol concentration before transplantation was 126.7 +/- 38.6 ng mL-1, while it decreased to 4.1 +/- 2.5 ng mL-1 within the period characterized by a cumulative dose of prednisolone from 300 to 700 mg. A statistically significant high incidence (P less than 0.01) of acute rejections was observed in low HPA responders; (mean cortisol concentration during prednisolone treatment exceeded 3.0 ng mL-1), 6 of 12 with a low HPA response to prednisolone showed signs of rejection, while none of the 7 with a high HPA response showed signs of rejection. The concentrations of prednisolone suppressing the in-vitro response of pretransplant lymphocytes to concanavalin A by 50% (ID50) were determined. Lymphocytes from 8 patients were extremely insensitive (ID50 greater than 500 ng mL-1), and 5 of the 8 showed signs of rejection. Lymphocytes from the other 11 patients showed high sensitivity (ID50 less than 500 ng mL-1), and only one of those showed signs of rejection. Thus, a significantly high incidence of rejection was observed in low lymphocyte-responders to prednisolone (P less than 0.05). The results suggest that an insensitive endocrine response to prednisolone correlates with an impaired lymphocyte response to the steroid, and that both of the indices are related to occurrence of rejection. Evaluation of these pharmacodynamic parameters in combination may serve as a guideline for successful immunosuppressive therapy in renal transplantation.