Pharmacodynamic assessment of the in vivo cyclosporine effect on interleukin-2 production by lymphocytes in kidney transplant recipients

Abstract

There are presently no monitoring tools to assess the immunosuppressive effect of cyclosporine (CsA) in vivo, since the mode of drug action is incompletely understood in man. Experimental in vitro studies suggest that CsA causes reversible inhibition of T helper cell generation of interleukin-2 (IL-2). Therefore the present study examined the effect of CsA administered in vivo on the capacity of kidney transplant recipient lymphocytes to generate IL-2 after mitogen (phytohemagglutinin [PHA]) stimulation. IL-2 production was measured by the capacity of lymphocyte supernates to trigger proliferation of a human IL-2-dependent T cell line. Peripheral blood lymphocytes (PBL) from CsA-Pred treated recipients displayed 40.6% inhibition (1.14 +/- 0.06 U/ml, n = 117, P less than 0.001) of IL-2 production compared with normal individuals (1.93 +/- 0.04 U/ml, n = 164). Dialysis patients did not display inhibited IL-2 production. The inhibition of IL-2 generation was observed in patients treated solely with CsA without supplemental corticosteroids (1.24 +/- 0.12 U/ml, n = 25; 35.8% inhibition, P less than 0.001). CsA did not inhibit the expression of the IL-2 receptor: 4.15 +/- 11.2% and 63.1 +/- 10.3 of normal lymphocytes and 36.7 +/- 9.8% and 60.4 +/- 12.2% of CsA-treated patient lymphocytes expressed anti-IL-2 receptors after 24 or 48 hr of PHA stimulation, respectively. Serial posttransplant studies in individual patients confirmed no inhibition of IL-2 generation pretransplant (1.94 +/- 0.07 U/ml) followed by a high degree of inhibition thereafter, namely 0.87 U/ml (55.0% inhibition) at 1 week, 1.15 U/ml (40.6% inhibition) at 2 weeks, 0.42 U/ml (78.2% inhibition) at 3 weeks, and 0.99 U/ml (48.7% inhibition) at 4 weeks. There was a correlation between the occurrence of rejection episodes in the 7 patients who suffered this event, and IL-2 generation by patient PBL. Before pulse therapy there was no inhibition of IL-2 generation (2.39 U/ml; -23.8 inhibition), documenting a poor level of immunosuppression in these patients. At 1, 2, 3, or 4 days after corticosteroid pulse therapy, PBL displayed 39.4%, 57.0%, 50.0% and 49.2% inhibition, respectively. These findings suggest not only that CsA treatment impairs the generation of IL-2 by patient lymphocytes, but also that failure to display this response is associated with a poor level of immunosuppression and allograft rejection. These studies provide a foundation for serial analyses of IL-2 generation, in order to dissect its utility as a pharmacodynamic parameter to assess the level of CsA-induced immunosuppression.