Background: Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. There is an urgent need to develop new therapeutic approaches against skin fibrosis. Although intravenous immunoglobulin (IVIG) may be one of the promising treatments, the mechanisms by which IVIG improves the fibrosis of SSc remain unknown.
Objectives: To compare the cytokine profile in the sera and skin of SSc patients before and after IVIG administration, and try to clarify the mechanism of the effect of IVIG.
Methods: Each three patients received 5-day administration of IVIG, or the same dose of physiologic saline for placebo. Cytokine levels were determined by ELISA array, immunostaining, and real-time PCR.
Results: Cytokine array revealed that the serum levels of IFN-g and IL-12, representative Th1 cytokines, were increased by IVIG treatment, but not by placebo. The percentage of IFN-g- and IL-12-positive cell number / CD4-positive T lymphocyte cell number was also significantly increased by IVIG in SSc skin. Furthermore, mRNA expression of IFN-g and IL-12 in SSc skin tissue was significantly up-regulated after IVIG treatment.
Conclusion: The expression of Th1 cytokine is reported to be decreased in SSc. Our study suggested IVIG recovered the suppressed levels of Th1 cytokines, and that the treatment improves skin fibrosis by correcting the Th1/Th2 balance. In order to facilitate the clinical use of IVIG for SSc, it is necessary to perform a lager study in the future.