CD4 and rheumatoid arthritis: Activated HLA-DR+ CD4+ T cells have also been identified in immune-mediated diseases affecting the synovial fluid in juvenile idiopathic arthritis (JIA)34 and rheumatoid arthritis (RA) patients.35 In JIA patients, activated effector T helper cells are resistant to Treg-mediated suppression, suggesting an important pathogenic role for this activated phenotype.