IFNG and systemic lupus erythematosus: SLE and RA are both driven by activated macrophages (Udalova et al, 2016; Ma et al, 2019) as a result of known (for SLE) or hypothesised (RA) upregulation of IFN‐γ signalling (Harigai et al, 2008; Rönnblom & Leonard, 2019; Kato, 2020).