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

Abstract

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-beta 1), 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-beta 1 levels in sera, plasma, and supernatants, and an imunofluorescence 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-beta 1 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-beta 1 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.