Abnormal levels of T cell-derived cytokines, including TNFα, IL-6, IL-10 (Sato et al., 2001), IL-17, IL-4, and IL-13 (Fuschiotti et al., 2009; Hügle et al., 2013; Kang et al., 2019), have been found in the serum of SSc patients. Here, IL4 is linked to systemic sclerosis.