Background and objective Recent work has shown that systemic autoimmunity precedes inflammation of the synovium in rheumatoid arthritis (RA). Not much is known about the balance between regulatory and effector CD4+ T-helper cell subsets during the earliest phases of systemic autoimmunity. Therefore, we investigated CD4+ T-helper cell subsets in lymph node biopsies and peripheral blood during the earliest phases of RA.
Methods Nineteen individuals with arthralgia but without arthritis, who were positive for IgM rheumatoid factor (IgM-RF) and/or anti-citrullinated protein antibodies (ACPA; RA-risk individuals) and 17 early RA patients (disease duration less than 1 year and naïve for disease-modifying antirheumatic drugs and biologics) were included. For comparison we included 19 healthy controls (HCs). All study subjects underwent ultrasound-guided inguinal lymph node biopsy. CD4+ T-helper cell subsets were analysed by flow cytometry. Cytokine profiles (frequencies of positive cells and production per cell based on mean fluorescent intensity (MFI)) were determined after stimulation with Phorbol Myristate Acetate (PMA) and Ionomycin in the presence of Brefeldin A and Golgi Stop.
Results The frequencies of total lymphoid CD4+ T cells were comparable between early RA patients, RA-risk individuals and HCs. The frequency of lymphoid Th1 cells (CXCR3+CCR6-CCR4-) was significantly higher in early RA patients compared with HCs (p < 0.01).
Frequencies of lymphoid CD4+IL-4+ (p < 0.05) and CD4+IL-10+(p < 0.01) T cells were lower in RA-risk individuals compared with HCs. In peripheral blood frequencies of CD4+IL-17A+ T cells were higher in early RA patients compared with RA-risk individuals (p < 0.05) and HCs (p < 0.05). In addition, the frequency of CD4+IL-10+ T cells was lower in peripheral blood of RA-risk individuals compared with HCs (p < 0.05).
Of interest, lymphoid CD4+ T-helper cells produced lower levels of cytokines (IFN-y, IL-4, IL-17A and IL-10) per cell (based on MFI) in both RA-risk individuals and early RA patients compared with HCs.
Conclusions The decreased frequency of CD4+IL-10+ T cells in RA-risk individuals compared with HCs observed in both peripheral blood and lymphoid tissue indicates that a reduction in the expression of regulatory cytokines by CD4+ T cells precedes the development of clinically manifest RA. These data also suggest that the subsequent development of clinical signs and symptoms is associated with an increase in pro-inflammatory cytokine production by CD4+ T cells, as shown here for IL-17A expression. Changes in pro-inflammatory and regulatory CD4+ T-helper cell subsets during different stages of RA development may provide new preventive and therapeutic targets.