ABSTRACT
            Background and Objectives: T helper (Th) lymphocytes play a key role in the pathogenesis of autoimmune diseases. As a new subset of lymphocytes, Th9 is thought to be involved in a wide range of disorders including rheumatoid arthritis (RA). In this study, we evaluated frequency of Th9 and Th2 cells and its correlation with disease activity in patients with different stages of RA.
            Methods: The frequency of circulating interleukin 9- and/or interleukin 4-producing CD3⁺CD8^-T cells was determined among 41 patients with established RA, 14 patients with very early RA (VERA) and 23 healthy controls by flow cytometry analysis. Then, correlation of cell frequencies with disease activity score 28 (DAS-28) was assessed. Serum levels of interleukin 6 and anti-citrullinated peptide antibodies were measured by enzyme-linked immunosorbent assay.
            Results: Frequency of Th9 cells was significantly higher in RA patients compared to healthy controls (P=0.009). Moreover, mean percentage of circulating Th9 cells in patients with inactive VERA was significantly higher than that in those with active disease (P=0.046). In addition, mean percentage of Th9 cells had a negative correlation with the DAS-28 (r=-0.568, P<0.05). There was no significant correlation between the mean serum level of interleukin 6 and percentage of Th2 and Th9 cells (P>0.05).
            Conclusion: Our results suggest that Th9 cells may have a potential role in RA initiation. Thus, targeting Th9 cells could be a promising strategy for advanced RA therapies.
            Keywords:  Rheumatoid arthritis, Th2 cells, Th9 cells.