Indeed, the IFN signature has been observed in the peripheral blood, skin, and lungs of SSc patients [35, 36], and circulating SSc pDCs secrete elevated levels of IFN-I due to the aberrantly expressed Toll-like receptor (TLR) 8 as well as TLR7 and TLR9. This evidence concerns the gene TLR9 and systemic sclerosis.