PRTN3 and rheumatoid arthritis: This interaction between the autoantibodies and increased inflammatory process is further supported by a 2014 cohort study published by Sokolove et al.18 They grouped 1488 US veterans with RA according to their antibody status (ACPA+/RF+, ACPA-/RF+, ACPA+/RF-, ACPA-/RF-) and compared the levels of disease activity and serum levels of cytokines in each group.