Serum soluble IL-2 receptor as a marker of lymphocyte activation in some autoimmune diseases. Effect of immunosuppressive therapy.

Our experience regarding serum soluble interleukin-2 receptor (sIL-2R) measurement as a marker of lymphocyte activation consists of patients with autoimmune disease: 37 with systemic lupus erythematosus (SLE), 23 with autoimmune hepatitis (AIH), 74 with inflammatory bowel disease and six with Wegener's granulomatosis (WG). The influence of immunosuppressive therapy has also been assessed. Serum sIL-2R in SLE is significantly higher than in healthy controls and good correlation is found between sIL-2R and disease activity. Severity of kidney inflammation in lupus nephritis can be reflected by the increased excretion of sIL-2R. It was found that sIL-2R level significantly falls when the disease becomes clinically inactive after immunosuppressive therapy, but in many cases (up to 50%) it does not reach normal levels. The last finding suggests that lymphocyte activation may still be present even though the disease is considered inactive under clinical criteria and support the need of prolonged immunosuppression after the first signs of remission. In AIH the serum levels of sIL-2R are elevated in all patients with active disease; all cases with "highly active" disease have significantly higher concentrations than patients with "mild activity". A good correlation has been demonstrated between elevated serum sIL-2R values and anti-asialoglycoprotein receptor (ASGPR) titer (the specific marker of AIH). The follow-up study showed a significant decrease of both sIL-2R levels and anti-ASGPR titer after 3-9 month immunosuppressive therapy. The findings support that sIL-2R and anti-ASGPR titer could serve as reliable humoral markers for disease-specific activity. Compared with inactive ulcerative colitis (UC) and Crohn's disease (CD), significantly higher levels of sIL-2R were present in the serum of patients with active disease, and in inactive disease than in healthy age-matched controls. Methotrexate (MTX) therapy of patients with refractory UC resulted in sIL-2R decrease at the end of therapeutic period (20 i.m. injections of once a week 25 mg), good responders showing > 50% decrease even at 5-7 weeks of treatment. Serum sIL-2R is elevated in all six patients with WG. Contrary to anti-neutrophil cytoplasmic antibodies (ANCA), sIL-2R remains elevated above cut-off for normal range, despite clinical improvement following immunosuppressive treatment. The last observation suggests that serum sIL-2R is not a good measure of the disease activity and argue for the need of longer immunosuppressive therapy just after the first days of clinical remission.