Serum soluble interleukin 2 receptor in systemic lupus erythematosus: effects of disease activity and infection.

Serum soluble interleukin 2 receptor (sIL2R) was measured in patients with active and inactive systemic lupus erythematosus (SLE). The concentration of sIL2R was higher in inactive SLE than in normal controls and was significantly increased in active compared with inactive SLE. When patients with active SLE were followed up serially it was found that the sIL2R concentration fell when the disease became inactive. There was no statistically significant association between sIL2R and the grades of disease activity, however. In patients with either active or inactive SLE and infection the sIL2R concentration was much higher than in those without infection. Chronic infection (tuberculosis or candida) was associated with a much higher concentration of sIL2R than pyogenic or herpes zoster infection. The sIL2R concentration helps to distinguish infection in patients with SLE.