A critical analysis of soluble interleukin-2 receptor levels in kidney allograft recipients.

Soluble interleukin-2 receptor (sIL-2R) was measured by the Cellfree Kit (T Cell sciences) in 103 pretransplant and 1590 posttransplant samples from 103 patients with cadaveric kidney allografts. The mean values (+/- SD) detected in pretransplant sera were significantly higher (1932 +/- 1389 U/ml) than in 72 healthy adults (267 +/- 139 U/ml), but after transplantation they continuously fell towards normal levels within the first 3 postoperative weeks. Recipients with acute rejection episodes showed higher sIL-2R levels (1762 +/- 904 U/ml) than those with stable transplants at discharge (937 +/- 398 U/ml). Highest values were detected during antirejection therapy with antithymocyte globulin (4996 +/- 2166 U/ml) or OKT3 (5905 +/- 3910). Increases were also observed during bacterial and viral infections and even, in some cases, without any apparent cause. Because of this lack of specificity, elevated sIL-2R levels should be interpreted cautiously. Nevertheless, sIL-2R level can be useful for monitoring kidney allograft recipients. Increases point to a cellular immune activation process and can predict rejections or infections.