The Phenotype of Circulating Follicular-Helper T Cells in Patients with Rheumatoid Arthritis Defines CD200 as a Potential Therapeutic Target

Rheumatoid arthritis (RA) is a systemic autoimmune disease primarily affecting synovial joints in which the development of autoantibodies represents a failure of normal tolerance mechanisms, suggesting a role for follicular helper T cells (T(FH)) in the genesis of autoimmunity. To determine whether quantitative or qualitative abnormalities in the circulating T(FH) cell population exist, we analysed by flow cytometry the number and profile of these cells in 35 patients with RA and 15 matched controls. Results were correlated with patient characteristics, including the presence of autoantibodies, disease activity, and treatment with biologic agents. Circulating T(FH) cells from patients with RA show significantly increased expression of the immunoglobulin superfamily receptor CD200, with highest levels seen in seropositive patients (P = 0.0045) and patients treated with anti-TNFα agents (P = 0.0008). This occurs in the absence of any change in T(FH) numbers or overt bias towards Th1, Th2, or Th17 phenotypes. CD200 levels did not correlate with DAS28 scores (P = 0.887). Although the number of circulating T(FH) cells is not altered in the blood of patients with RA, the T(FH) cells have a distinct phenotype. These differences associate T(FH) cells with the pathogenesis of RA and support the relevance of the CD200/CD200R signalling pathway as a potential therapeutic target.