Paradoxical response to tacrolimus assessed by interleukin-2 gene expression

The calcineurin inhibitors cyclosporine and tacrolimus are potent immunosuppressive drugs, used mainly after organ transplantation. Methods to monitor their pharmacodynamic effects are not well established.

Whole blood samples from healthy volunteers (n = 16) were incubated for 24 hours in culture medium; each sample was preincubated for 2 hours with or without tacrolimus. An identical procedure was performed for 7 samples using blood from renal transplant patients before transplantation. Following the culture period, total RNA was isolated and quantitative reverse transcriptase polymerase chain reaction, using TaqMan probes, was employed to quantify interleukin-2 (IL-2) mRNA expression, and IL-2 mRNA copy number was reported by reference to a standard curve.

IL-2 mRNA synthesis was suppressed by the presence of tacrolimus in most cases, compared with a control sample. However, some samples demonstrated up-regulation of mRNA expression. In the patient samples, there was up-regulation of IL-2 mRNA in two samples and, after transplantation, these patients developed acute rejection.

Quantitative measurement of cytokine IL-2 regulated gene expression may represent a method to assess the efficacy of calcineurin inhibitor drugs.