First we investigated by immunohistochemistry the presence of PADI enzymes required for citrullination in LN tissue and cultured LNSCs of a small cohort of individuals (healthy individuals, RA-risk ACPA− individuals, RA-risk ACPA+ individuals, RA ACPA− patients, and RA ACPA+ patients; for each subgroup n = 3, total n = 15). Here, PRTN3 is linked to rheumatoid arthritis.