PRTN3 and rheumatoid arthritis: Up to this point, several RA-ILD-associated peptides have been identified, including anti-citrullinated peptide antibodies (ACPA), anti-vimentine antibodies, citrulline isoforms of heat shock protein 90, matrix metalloproteinase 1 (MMP) and inducible protein interferon-gamma 10 [10,11,12].