Reduction of immunosuppressive load in renal transplant recipients with a low donor-specific cytotoxic T-lymphocyte precursor frequency is safe

Background. Tapering of immunosuppressive medication is indicated to prevent long-term side effects. Recently, we have shown that renal transplant recipients can safely be converted from calcineurin inhibitors to MMF or AZA when their donor-specific cytotoxic T-lymphocyte precursor frequencies (CTLpf) are below 10/10(6) PBMC. We wondered whether a low CTLpf also had predictive value when immunosuppressive medication was reduced in patients only on MMF or AZA and steroid medication. Methods. Renal transplant recipients with stable renal function at least 2 years after transplantation and with low (< 10/10(6) PBMC) CTLpf were included. Their MMF or AZA dose was reduced to 75% and to 50% of the original dose at 4 months and 8 months after inclusion. Endpoint of the study was 12 months after inclusion or developing acute rejection. Results. Forty-five patients have reached the 1-year follow up endpoint. Their median time after transplantation was 4.2 years (range 2.0-1.5.5 years). Acute rejection was seen in one patient only (who had discontinued all his medication). Conclusion. In patients with low CTLpf long after kidney transplantation, a 50% reduction of immunosuppression is safe and further decreasing their immunosuppressive load is the obvious next step.