Lymphocyte modulation by tofacitinib in patients with rheumatoid arthritis

Summary Tofacitinib is an oral small molecule targeting the intracellular Janus kinase–signal transducer and activator of transcription (JAK‐STAT) pathways approved for the treatment of active rheumatoid arthritis (RA). We investigated the effects of tofacitinib on the response of RA lymphocytes to B and T cell collagen epitopes in their native and post‐translationally modified forms. In particular, peripheral blood mononuclear cells (PBMCs) from patients with RA and healthy subjects were cultured with type II collagen peptides (T261‐273, B359‐369, carT261‐273, citB359‐369) or with phorbol myristate acetate (PMA)/ionomycin/CD40L in the presence or absence of 100 nM tofacitinib for 20 h and analyzed by fluorescence activated cell sorter (FACS). Cultures without brefeldin A were used for cytokine supernatant enzyme‐linked immunosorbent assay (ELISA) analysis. Tofacitinib down‐regulated inflammatory cytokines by stimulated B [interleukin (IL)‐6 and tumor necrosis factor (TNF)‐α] and T [interferon (IFN)‐γ, IL‐17 or TNF‐α] cells in the short term, while a significant reduction of IL‐17 and IL‐6 levels in peripheral blood mononuclear cell (PBMC) supernatant was also observed. IL‐10 was significantly reduced in collagen‐stimulated B cells from patients with RA and increased in controls, thus mirroring an altered response to collagen self‐epitopes in RA. Tofacitinib partially prevented the IL‐10 down‐modulation in RA B cells stimulated with collagen epitopes. In conclusion, the use of tofacitinib exerts a rapid regulatory effect on B cells from patients with RA following stimulation with collagen epitopes while not reducing inflammatory cytokine production by lymphocytes.