Serum interleukin-2 and soluble interleukin-2 receptor in renal transplant recipients

Interleukin-2 (IL-2) and soluble interleukin-2 receptor (sIL-2R), released during T-lymphocyte activation, were measured in serial samples of serum from 32 patients with renal allografts and other uremic patients. Patients undergoing chronic hemodialysis had elevated sIL-2R levels (1,801.93 ± 753.23 U/mL) which dropped after stable renal transplantation (822 ± 438 u/mL). However, these values were higher than those of a normal control group (397.3 ± 84.5 u/mL, p <0.01). Marked elevation of sIL-2R (1,503.78 ± 640 u/mL) was noted in patients with acute rejection episodes compared to those in a stable allograft condition (p <0.02) and those with cyclosporine nephrotoxicity (793.2 ± 245.2 u/mL, p <0.01). Acute tubular necrosis and infection also showed a comparable rise in the sIL-2R level. The increase in sIL-2R with rejection was found one to four days earlier than the clinical diagnosis of acute rejection. There was a marked rise in the serum IL-2 level of uremic and post-transplant patients when compared to normal subjects (34.76 ± 32.16 u/mL and 9.3 ± 12.7 u/mL vs 4.38 ± 3.38 u/mL, p <0.001), but no significant differences were found between the IL-2 level of patients with acute rejection and cyclosporine nephrotoxicity or acute tubular necrosis (3.74 ± 4.51 u/mL, 1.57 ± 1.25 u/mL and 6.73 ± 6.3 u/mL, p > 0.05). The diagnostic value of sIL-2R assay was more meaningful than that of IL-2. Serial monitoring of sIL-2R levels could be valuable as an indication of immunologic activation in renal allograft recipients. It is particularly helpful in differentiating the allograft dysfunctions of rejection and cyclosporine nephrotoxicity.