C3 and Sjogren syndrome: Existing studies revealed that iguratimod reduced the production of cytokines including IFN‐1β, IL‐6, IL‐8 and IL‐17A both in vitro and in vivo.20 Further, iguratimod could reduce immunoglobulin production in both mice and humans with RA.21 Iguratimod could also attenuate proteinuria and kidney injury in MRL/lpr lupus mice, and improve serum markers such as anti‐dsDNA and serum C3.12 In addition, there are some studies published in Chinese which showed iguratimod treatment was effective for primary Sjögren's syndrome and patient's serum Ig was decreased as well.