Within the SE-positive subset, anti-B19 and anti-EBV IgG levels were significantly lower in RA and ACPA-positive RA (and also in ACPA-negative RA for EBV) compared to controls, while anti-B19 IgG levels were significantly lower in ACPA-positive RA compared to ACPA-negative RA, when comparisons were made within the SE-negative subset. This evidence concerns the gene PRTN3 and rheumatoid arthritis.