Interestingly, anti–CCP‐positive RA patients had higher serum IL‐29 levels than that in healthy controls and anti–CCP‐negative RA patients.32 In RA synovial fluid, increased level of granzyme M (GrM) could induce the release of IL‐29.33 In SLE patients, IL‐29 expression was increased in SLE patients as compared to healthy controls. Here, IFNL1 is linked to systemic lupus erythematosus.