IFIT2 and infection: These data suggest that there are three tonic ISG RNA subclasses due to a type of regulation independent of canonical interferon signaling and not a common infection because: 1) each profile reflects the median expression for tens to hundreds of samples, 2) interferon expression is low overall for all tissues examined, and 3) ISGs in the low class, like OAS1 and IFIT2, would be expressed at markedly higher levels in infected tissues.