In RA, T cells recognizing Cit and other self-antigens, such as native and posttranslationally modified CII259-273, are identifiable with peptide-HLA-DR tetramers and are found in low numbers in peripheral blood and synovial fluid of patients with HLA-DRB1*04:01 and *01:01 (20–25). Here, HLA-DRB1 is linked to rheumatoid arthritis.