Summary

Systemic lupus erythematosus (SLE) is characterised by generalised immune activation. Part of this might be explained by a decreased rate of apoptosis, possibly related to eleva-ted levels of soluble Fas (sFas) which can inhibit Fas mediated apoptosis of lymphocytes. In order to substantiate the relation between levels of sFas and lymphocyte activation in SLE we monitored sFas levels, lymphocyte activation and disease activity in twenty five SLE patients. SLEDAI-scores were registered and sera were assayed for sFas levels by an enzyme-linked immunosorbent assay. Flow cytometry was used to monitor the state of activation of lymphocyte subsets. Eighteen healthy, age-matched, volunteers served as controls. Soluble Fas levels were elevated in SLE patients (n=25) compared to healthy controls (n=18, p=0.002). Soluble Fas levels correlated with SLEDAI-scores (r=0.45, p=0.02). Levels of sFas correlated with the percentages of activated B cells defined as CD20+CD38+ cells (r=0.47, p=0.009). Percentages of CD20+CD38+ cells were increased in quiescent SLE compared to healthy controls (p=0.003). The expression of activation markers on CD4+ T-lymphocytes (IL-2R, p=0.04; HLA-DR, p=0.01) and CD8+ T-lymphocytes (HLA-DR, p=0.007) was increased as well in quiescent SLE compared to controls. Activation markers on all lymphocyte subsets tended to increase further during disease activity. No correlation was observed between percentages of activated T-lymphocyte subsets and levels of sFas. In conclusion, soluble Fas levels are increased in SLE patients and correlate with disease activity as measured by the SLEDAI-score. B and T cell subsets are activated even during quiescent SLE. Serum levels of sFas do correlate with percentages of activated B cells but not with that of activated T cells