We examined cerebrospinal fluid (CSF) samples from 12 patients with SLE and active central nervous system (CNS) involvement for their levels of the following cytokines: interleukin-1 (IL-1) by means of two different assays--the IL-1 responsive murine cell line LBRM 33-la5 and an ELISA for IL-1 alpha; IL-2 by means of the CTLL cell line responsive to it; and interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF) both determined by a specific ELISA. We found that SLE CSF had significantly higher levels of IL-1 and IL-6 than did those obtained at surgery from eight controls without inflammatory neurologic disease. IL-2 and TNF were not detectable in any of the CSF samples. We also studied the status of activation in CSF T cells using monoclonal antibodies against early (anti-IL-2R (CD25) and anti-transferrin (CD71)), late (anti-T10) and very late (anti-VLA-1) activation antigens, and found increased percentages of T10-bearing (18 +/- 2 vs 3 +/- 0.7%) and VLA-1-bearing T cells (12 +/- 2 vs 0.7 +/- 0.2%) in SLE patients as compared to controls (both P < 0.01). Levels of IL-1 and IL-6 correlated with T10 and those of IL-1 correlated also with VLA-1. Markers of early T-cell activation did not differ in SLE and control CSF. Because of these findings we analysed the effect of recombinant IL-1, IL-6 or normal CSF on normal T cells and found that they did not induce the expression of activation markers.(ABSTRACT TRUNCATED AT 250 WORDS)