Galectin-9 expression correlates with efficacy of tacrolimus therapy in rheumatoid arthritis

Abstract Background: The calcineurin inhibitor tacrolimus (TAC) is the second-line treatment for rheumatoid arthritis (RA). Galectin-9 (Gal-9) is a multifunctional immunomodulatory factor highly expressed in RA synovial tissues and synovial fluid. This study aimed to investigate the expression of Gal-9 and its correlation with disease activity and response to TAC in RA patients.Methods: Active RA patients were enrolled and treated with TAC alone or in combination with methotrexate and/or prednisone for 12 weeks in a prospective cohort study. Clinical and immunological parameters were recorded at baseline and at week 12. We measured Gal-9 expression in different subsets of peripheral blood mononuclear cells using flow cytometry and assayed Gal-9 levels in plasma. We also tested cytokine levels in plasma by ELISA. Results: The disease activity of RA patients notably decreased after TAC treatment. At baseline, the percentages of CD4+ T cells and T regulatory cells (CD4+CD25+CD127low) expressing Gal-9 were higher in the group with severe disease than in mild or moderate groups. After TAC treatment in RA patients, the Gal-9 expression in CD3+, CD4+, CD8+ and CD4-CD8- cell subsets decreased, as well as Gal-9 mean fluorescence intensity in CD3+, CD4+ and CD8+ T cells. Similarly, plasma Gal-9 levels were lower at week 12 than at baseline. Good responders showed significantly lower Gal-9 expression on CD3+ and CD4+ T cell subsets as well as lower plasma Gal-9 levels than poor responders. Gal-9 expression positively correlates with disease activity in RA patients.Conclusion: Gal-9 can be regarded as a new biomarker for evaluating RA activity and efficacy of TAC.