PRTN3 and rheumatoid arthritis: To address these questions, we assemble individuals who are ‘At-Risk’ for RA as defined by the presence of ACPA (in particular, anti-cyclic citrullinated peptide antibodies [anti-CCP3], a test with high specificity for RA and future RA22–24) as well as individuals with anti-CCP3 positive Early RA and anti-CCP3 negative controls and assess immunologic and epigenetic changes that are associated with the ACPA+ “at-risk” state.