Genetics of rheumatoid arthritis: 2018 status 

Between 70% and 80% of patients with RA have autoantibodies such as Rheumatoid Factor (IgM antibody against IgG Fc region),and anti-citrullinated protein antibodies (ACPA), suggesting that RA is an autoimmune disease.(1)

 

Image Source:  Medicosis Perfectionalis, Anti-Cyclic Citrullinated Peptide (anti-CCP)   https://www.youtube.com/watch?v=EL53gN_Q3oY