A multicenter study to evaluate a novel assay for quantitation of soluble interleukin 2 receptor in renal transplant recipients.

The clinical utility of monitoring soluble interleukin 2 receptor (sIL-2R) as an indicator of immune stimulation in renal transplant patients was evaluated in a retrospective study at 3 centers. Serum samples (n = 2360) were obtained from 86 (17 living related donor, 69 cadaver) transplant recipients. The patients had received either triple therapy (n = 35) or antilymphocyte antibody induction therapy followed by triple therapy (n = 51). The mean period of postoperative observation was 118 days (range, 6-349 days). Serum sIL-2R concentrations were quantitated by an automated microparticle enzyme immunoassay (MEIA) (Abbott Diagnostics) in which sIL-2R was captured by 7G7/B6 monoclonal antibody-coated microparticles and detected by an immunospecific rabbit antihuman sIL-2R-alkaline phosphatase conjugate. A distinct advantage of the technique was rapid turn-around time: 1-24 results were obtained in less than 50 min. Cyclosporine trough concentrations were determined by radioimmunoassay or high-performance liquid chromatography. Diagnosis of rejection was established by clinical and histological criteria. The mean sIL-2R concentration in patients receiving antilymphocyte antibody induction therapy increased from 3486 +/- 1729 U/ml (+/- SD) at the time of transplant to a maximum of 7395 +/- 7101 U/ml on the third day posttransplant; this increase was not observed in patients receiving triple therapy (P less than 0.0001). By the sixth day of posttransplant, there were no differences in sIL-2R levels in the two groups. Fifty rejection episodes were observed in 29 patients on triple therapy. The mean sIL-2R concentration rose from 3022 U/ml at the data point prior to rejection to 3524 U/ml at the time of rejection. Thirty-four rejection episodes were observed in 26 patients receiving induction therapy. The mean sIL-2R concentration was 3015 U/ml at the data point prior to rejection and 4815 U/ml at the time of rejection. The sIL-2R concentrations began increasing earlier and rose higher in rejecting patients who received induction therapy than in those receiving triple therapy. Early posttransplant sIL-2R levels increased significantly more in cadaver recipients than in LRD recipients, reaching a maximum on day 2 posttransplant (P less than 0.001). Prerejection sIL-2R concentrations were significantly lower in LRD recipients than in cadaver recipients (2248 U/ml vs. 4290 U/ml, P less than 0.02), as were sIL-2R levels at the time of diagnosis of rejection (2800 U/ml vs. 4832 U/ml, P = 0.01). The mean sIL-2R level in stable long-term graft recipients was 2110 U/ml, with approximately 90% of values less than 3000 U/ml.(ABSTRACT TRUNCATED AT 400 WORDS)