Changes in plasma levels of interleukin-2 receptor in relation to disease exacerbations and levels of anti-dsDNA and complement in systemic lupus erythematosus.

Interleukin-2 receptor (IL-2R) is expressed and released predominantly by activated T cells. In order to investigate whether disease exacerbations of systemic lupus erythematosus (SLE) are preceded by T cell activation, we prospectively measured levels of IL-2R once a month, from 6 months prior to exacerbations until 1 month afterwards. To assess the temporal relation between T cell activation and B cell activation, we measured, in addition, levels of anti-dsDNA, complement C3/C4, and total IgG. During a mean follow-up period of 23 months, 40 exacerbations occurred in 21 out of the 71 participating patients. For the present study one exacerbation per patient was evaluated. During exacerbation levels of IL-2R were increased in 18 out of the 21 cases and correlated with levels of anti-dsDNA (P less than 0.02), C3 (P less than 0.02), and C4 (P less than 0.01), but not with the score of the disease activity index. Levels of IL-2R rose prior to the exacerbation (P less than 0.02) and fell afterwards following treatment (P less than 0.05). Even in the absence of disease activity or during minor disease symptoms IL-2R levels were higher (P less than 0.01) than in healthy controls. Sixteen out of the 21 exacerbations (76%) were preceded by a significant increase in IL-2R. Changes in levels of anti-dsDNA and complement C3/C4 tended to precede changes in levels of IL-2R. We conclude that increased levels of IL-2R, compatible with T cell activation, are present in SLE already during inactive disease. These levels further increased prior to exacerbations of disease. As such, IL-2R is an indicator of disease activity in SLE. Serial measurement of IL-2R is a sensitive test for predicting disease exacerbations of SLE.