CCR6 and systemic sclerosis: The roles of Th1 and Th17 in SSc pathogenesis became evident when high levels of CXCL9, CXCL10 (CXCR3 ligands) [55], and CCL20 (CCR6 ligand) [56] were detected in SSc skin lesions, indicating an active migration of T cells bearing these receptors (Th1, Th17, and Th1/17 cells) to these sites.