[Serum soluble interleukin 2 receptor levels in patients with diffuse connective tissue diseases]

Soluble interleukin 2 receptor (SIL-2R) levels in serum appear to reflect the status of lymphocytic activation and proliferation. We examined the levels of serum SIL-2R in 65 patients with diffuse connective tissue diseases by using ELISA method. The mean levels of serum SIL-2R were respectively 0.46 U/L, 0.53 U/L, 0.46 U/L in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and dermatomyositis during disease activity and were significantly higher than those in healthy controls (0.25 U/L). The levels of serum SIL-2R were 0.62 U/L and 0.60 U/L respectively in a patient with mixed connective tissue disease and a patient with systemic sclerosis. The levels of SIL-2R were respectively 0.24 U/L and 0.29 U/L in SLE and RA patients during clinical remission, being significantly lower than during disease activity. SLE patients with high SIL-2R levels were associated with high levels of 125I-DNA rate and erythrocyte sedimentation rate and lower levels of C3 complement components. The measurement of SIL-2R levels may be an useful indicator for monitoring disease activity in SLE and RA patients. Moreover it is a noninvasive method.