Early studies (Kuo et al., 2019; Zhang et al., 2019) with limited cell numbers resolved RA synovial myeloid cells into four subtypes, which included inflammatory IL1β+ monocytes that express NF-κB target genes and a distinct monocyte cluster that expresses high levels of ISGs and thus an IFN signature. Here, IFNA1 is linked to rheumatoid arthritis.