Longitudinal analysis of serum cytokine concentrations in systemic sclerosis: Association of interleukin 12 elevation with spontaneous regression of skin sclerosis

Objective. Skin sclerosis that progresses in the earlier disease phase in systemic sclerosis (SSc) spontaneously regresses thereafter. We investigated the relationship between changes of the serum cytokine profile and changes in skin fibrosis in patients with SSc. Methods. Serum cytokine levels were examined by ELISA using 180 sera samples from 26 patients with early diffuse cutaneous SSc (dcSSc) with mean disease duration of 2.1 years. The mean followup period was 4.9 years (range 2-8). Cytokine mRNA expression in the affected skin was quantified by real-time reverse transcription-polymerase chain reaction. Results. Modified Rodnan total skin thickness score decreased after 2, 4. and 6 years compared to that at first visit. Serum levels of the Th2 cytokines interleukin 6 (IL-6) and IL-10 and monocyte chemotactic protein-1 (MCP-1) were higher at first evaluation compared to healthy controls. while IL-4 levels were normal. Levels of all Th2 cytokines generally decreased as skin sclerosis regressed. Conversely, levels of serum IL-12, a Th1-inducing cytokine, were lower at first visit relative to controls, but increased by roughly 15-fold after 6 years to significantly higher levels than controls. Surviving dcSSc patients exhibited elevated IL- 12 levels compared to deceased patients. Serum levels of transforming growth factor-beta(1) (TGF-beta(1)), a fibrogenic cytokine, increased throughout followup, with slightly decreased levels at later timepoints. IL-12 rnRNA expression was upregulated in affected skin from patients with late-stage dcSSc, while TGF-beta(1) and MCP-1 expression was downregulated. Conclusion. These results suggest that a shift from Th2 to Th1 response correlates with improvement in skin fibrosis in SSc, and that IL-12 level is a serologically useful market for disease activity and prognosis.