IL6 and systemic sclerosis: In in vitro studies, skin dermal fibroblasts derived from SSc patients have been found to produce high levels of IL-6, and the complex of IL-6 and soluble IL-6 receptor (sIL-6R) has been shown to stimulate SSc fibroblasts via gp130 to differentiate and proliferate, resulting in collagen overproduction and fibrosis18, 21, 22, 23.