Most recently, ICs composed of DNA and CXCL4 (chemokine (C-X-C motif) ligand 4), a cytokine overexpressed in SSc skin, have been identified as novel TLR ligands in SSc, amplifying TLR9 activation and IFN-α production in plasmacytoid dendritic cells [37]. This evidence concerns the gene PF4 and systemic sclerosis.