TH9 lymphocytes in rheumatoid arthritis

The aim of this study was determine the prevalence of Th9 lymphocytes in RA patients and identify their possible association with the discontinuation of infliximab (IFX). Methods: We enrolled 55 consecutive RA outpatients: 15 not receiving any immunosuppressive drug; 20 responders to IFX treatment; 20 who had discontinued IFX because of adverse events or inefficacy and were being treated with other biological agents (ABA, TCZ, ETN or CTZ) and DMARDs. The matched control group consisted of 10 healthy subjects. Each subject underwent blood sampling for the isolation of peripheral blood mononuclear cells (PBMCs). The PBMCs were cultured with/without IFX 50 mg/L for 18 hours, and the percentage of Th9 cells was assessed by flow cytometry. Th9 lymphocytes were identified as IFNγ-, IL4-, IL17- , IL9-secreting CD4+ T cells. Results: Cytometric analysis revealed no significant decrease in the percentage of Th9 cells after IFX exposure in any of the groups, but there were significantly fewer cells in the healthy controls than the RA patients both before and after the IFX stimulation assay. The higher frequency of Th9 cells in the patients was not associated with higher levels of anti-nucleus autoantibodies or other auto-antibody subsets, or with a higher likelihood of experiencing an adverse event or lack of efficacy on IFX treatment. Conclusions: IL-9 levels are increased in RA patients. Th9 cells are the major producers of IL-9, and their prevalence is higher in RA patients than in healthy subjects, although they do not seem to affect the outcome of biological therapies.