Peripheral blood mononuclear cells of patients with systemic sclerosis produce increased amounts of interleukin 6, but not transforming growth factor beta 1.

Objective. To assess the ability of peripheral blood mononuclear cells (PBMC) of patients with systemic sclerosis (SSc) to produce interleukin 6 (IL-6), transforming growth factor beta 1 (TGF-β1), to identify the IL-6 producer cells in the in vitro model, and to correlate these data with the clinical evidence of our patients. Methods. We used a sandwich ELISA to quantitate IL-6 and TGF-β1 levels in sera, plasma, and supernatants, and an immunofluorescence technique to evaluate IL-6 producing cells in our patients. Results. IL-6 was detected in sera from 8 of 20 patients and no controls (p < 0.05). A significant increase of IL-6 production was observed in both spontaneous and phytohemagglutinin (PHA) induced cultures of PBMC from patients with SSc vs controls. No differences in TGF-β1 production were observed, either in sera or supernatants, between patients and controls. A significant increase of IL-6 synthesizing cells was observed after 3 h of PHA stimulation in patients vs controls (p < 0.05). Conclusion. Spontaneous IL-6 production and the higher number of IL-6 producing cells in patients with SSc suggest that these cells have been already primed in vivo. The absence of PBMC primed for TGF-β1 production supports the hypothesis that cells other than lymphocytes produce and secrete this cytokine in the skin of patients. Higher serum levels of IL-6 observed in a subset of patients did not correlate with either severity or duration of disease.