Soluble interleukin 2 receptor (sIL-2R) levels in renal transplant recipients

Abstract: Background: Allograft rejection is associated with T cell activation. T cell activation leads to secretion of soluble IL-2 receptor and elevated serum soluble IL-2 receptor (sIL-2R) levels. However, the clinical implication of individual elevated sIL-2 receptor levels is unclear. We followed levels of sIL-2R pre- and post-transplantation to determine if sIL-2R levels predict rejection episodes or degree of graft function.

Materials and methods: Serum samples of 12 patients who underwent living or cadaveric renal transplant were followed weekly with serial sIL-2R levels. These levels were followed until the serum creatinine reached a baseline. Of the 12 patients, three patients developed delayed graft function. The remaining nine patients were followed for a period of 3 months. Sera of these nine patients in the initial 3 months post-transplant were monitored for sIL-2R levels. For comparison, sIL-2R levels were also measured in 150 healthy volunteers and five dialysis patients.

Results: Recipients undergoing severe rejection episodes had higher overall serum levels of sIL-2R (1515 ± 496 U/mL) as compared with recipients who had stable renal transplants and no episodes of rejection (698 ± 333 U/mL) (P = 0.034). Comparison of sIL-2R ratios (post-transplant sIL-2R level/pre-transplant sIL-2R level) revealed that ratios of 0.6 or higher were more frequently seen in patients who subsequently underwent severe rejection episodes. Dialysis patients were found to have higher sIL-2R levels (2605 ± 1312 U/mL) compared with renal transplant patients (1047 ± 192 U/mL) (P < 0.001) and healthy volunteers (349 ± 185 U/mL) (P < 0.001).

Conclusion: Our results suggest that individual levels of sIL-2R are not predictive of rejection in the early post-transplant period, but s-IL2R ratios greater than 0.6 may be predictive of severe rejection episodes.