In agreement with earlier studies we observed an IFN signature in PBMCs in RA36,37 where eight genes detected by microarray analysis in our cohort, namely, IFIT1, IFIT2, IFI44L, RSAD2, SERPING1, EPSTI1, RTP4, and ISG15 were identified in an earlier RA gene expression profiling study38. Here, ISG15 is linked to rheumatoid arthritis.