CCN2 and systemic sclerosis: Cells of the innate and adaptive immune system elaborate a variety of cytokines and chemokines in addition to TGF-β and IL-4 (such as IL-6, PDGF, IL-1, IL-13, IL-17, IL-5, MCP-1, and CTGF) that have been found to be increased in serum or in tissues in which excess connective tissue matrix is accumulating in SSc.