Other proposed molecules involved at different levels in the immune, inflammatory, and fibrotic response characterizing RA-ILD include matrix metalloproteinase 7 (MMP-7), C-X-C motif chemokine ligand 10 (CXCL10) (127), Dickkopf 1 (DKK1) (128), and soluble programmed death 1 (sPD-1) (129). Here, MMP7 is linked to rheumatoid arthritis.