Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of skin and internal organs. Its pathogenesis, which is still poorly understood, features three main pathogenic moments: an initial diffuse vasculopathy followed by low-grade inflammation and a subsequent tissue fibrosis. Numerous evidences support the role of a Th2-oriented immune response during both the inflammatory and the fibrotic phase of SSc.

Levels of IL-4, IL-13 and CXCL4 are higher in the serum of SSc patients compared to healthy controls. Fibrotic tissue in SSc displays a Th2 polarized CD4+ cell infiltration, influencing fibroblast phenotype and inducing collagen and extra cellular matrix protein synthesis. In tight skin mice the administration of neutralizing anti-IL-4 antibodies prevents the development of dermal fibrosis. Back-crossing these mice onto a genetic background that cannot respond to IL-4 prevents skin sclerosis. In SSc, CD8+ T lymphocytes secrete IL-13 and mediate dermal fibrosis and have skin-homing receptors. Incubation with healthy dermal fibroblasts results in elevation of extracellular matrix, which can be reduced with anti-IL13 antibodies. Specifically, IL-4 and IL-13 take part in the inflammatory phase, contribute to the transition from the inflammatory to the fibrotic phase and maintain a profibrotic state in affected organs, mediating the interaction between T cells and fibroblasts. Blocking the cross-talk between these cell types by acting on the soluble cytokines, on their receptors on cell surfaces or on intracellular signaling pathways could constitute a new therapeutic approach.