Increased circulating CD14brightCD16+ intermediate monocytes are regulated by TNF-α and IL-6 axis in accordance with disease activity in patients with rheumatoid arthritis

OBJECTIVES: Although circulating CD14brightCD16+ monocyte subsets are increased in inflammatory disease, the pathogenesis of the increase in the inflammatory condition of the cells is still unclear and the relationship to cytokines is unknown particularly in rheumatoid arthritis (RA). The purpose of this study was to investigate the influence anti-cytokine treatment has on CD14brightCD16+ monocytes in patients with RA. METHODS: Thirty-two RA patients and 14 healthy volunteers (HV) were enrolled in this study. All the patients had never been treated with methotrexate (MTX) or biological agents. Peripheral blood samples and clinical information of the patients were obtained at the time of 0, 12 and 24 weeks of treatment. Peripheral blood samples were also obtained from the HV. The expression levels of CD14 and CD16 on monocytes were measured by flow cytometry (FCM). RESULTS: Eight patients received anti-interleukin (IL)-6 receptor antibody, tocilizumab (TCZ) treatment alone, 12 patients received anti-tumour necrosis factor (TNF)-α antibody, adalimumab (ADA) with MTX treatment and the others received only MTX treatment. FCM analysis revealed that the proportion of CD14brightCD16+ monocytes significantly increased in patients at baseline compared with HV. The proportion of CD14brightCD16+ monocytes significantly decreased after TCZ, and ADA with MTX treatment. The proportion of intermediate monocytes was significantly and positively correlated with disease activity and it improved in accordance with the proportion of CD14brightCD16+ monocytes after inhibition of signal transduction of inflammatory cytokines. CONCLUSIONS: We showed that the population of CD14brightCD16+ monocytes significantly decreased with the change of disease activity by key cytokines, IL-6 or TNF-α signal blockade in RA. This result indicates that the proportion of those monocytes is important for reflecting disease activity in RA.