ISG15 and rheumatoid arthritis: Notably ISG15 eSNPs were significantly associated with altering expression of well-known type 1 interferon response genes (IFI27, IFI35, IFI44, IFIT1, IFIT3, IFIT5 and OAS1, figure 3A).13 The ISG15 transEQTL also correlated with synovial B cell infiltration as measured by CD20 histology consistent with our previous finding that type 1 interferon gene expression signature was associated with synovial B cell infiltration.14 A similar blood interferon gene signature has been reported by Cooles et al as a prognostic biomarker in early RA individuals treated with methotrexate-based DMARDs.15