IFNA1 and rheumatoid arthritis: The level of type I IFN bioactivity affects the clinical response to TNFα blockade in RA patients, although these results have not always been consistent.26 A better clinical response to TNF-antagonists associated with high baseline plasma levels of type I IFN25 might result from increased TNFα expression and an overall higher level of inflammatory activity in patients with “high” IFN signatures compared to “low” IFN signature subjects.