In addition, we found no significant increase in serum IFN activity in treatment-naive patients with RA, SSc, or MPA compared to that of healthy individuals (Fig. 1), which was in agreement with the findings by Hua et al. that there were no significant differences in plasma IFN activities between healthy individuals and RA patients in the assay using WISH cells and their expression of 5 IFNα-induced genes including our IFIT1, MX1, and PKR [34]. This evidence concerns the gene MX1 and rheumatoid arthritis.