Plasma interleukin-2 and a soluble/shed interleukin-2 receptor in serum of patients with Crohn's disease. Effect of cyclosporin.

Circulating concentrations of interleukin-2 (IL-2) and a soluble or shed form of the IL-2 receptor (sIL-2R) were determined by enzyme-linked immunosorbent assays (ELISA) in 61 patients with chronic active Crohn's disease (CD) initially and during a three month placebo controlled trial of cyclosporin 5-7.5 mg/kg/day. The baseline median (25-75% range) plasma IL-2 concentration was 0.6 ng/ml (0.3-2.85 ng/ml) in patients who did not receive prednisolone, 0.5 ng/ml (0.23-3.4 ng/ml) in patients who did (not significant), and 0 ng/ml (0-0.07 ng/ml) in control subjects (p less than 0.00001). The corresponding median serum sIL-2R concentrations were 747 U/ml (580-1287 U/ml), 540 U/ml (422-616 U/ml) respectively in CD patients (p = 0.006) and 320 U/ml (268-406 U/ml) in control subjects (p less than 0.00001). Increased concentrations of plasma IL-2 and serum sIL-2R were seen in 66% and 81% of the patients, respectively. A fall in serum sIL-2R was only seen in patients who improved with cyclosporin treatment (p = 0.006). At month 3 the median serum sIL-2R concentration was 440 U/ml (400-668 U/ml) v 801 U/ml (534-1067 U/ml) in patients not responding to cyclosporin (p = 0.003). No changes occurred in the placebo group. These results suggest that the IL-2 dependent pathway of immune activation is upregulated in vivo in CD and that cyclosporin may interfere with this process.