PF4 and fibrosis: The frequency of pDCs in BAL fluid correlates with severity of fibrosis on chest CT in SSc-ILD patients (59), while in SSc skin lesions, pDCs accumulate in perivascular regions and produce increased IFN-α and chemokine ligand 4 (CXCL4) via TLR8 and phosphoinositide 3-kinase-δ signaling (60, 61).