PRTN3 and rheumatoid arthritis: Similar associations were observed with ACPA(+) RA (Figure 1B), whereas aspartic acid at position 57 (57D, P = 0.0006, OR = 0.46, Pc = 0.0191, 95% CI 0.30–0.71) in the DRβ chain showed a slight protective association with ACPA(−) RA (Figure 1C).