Since TNF-stimulated fibroblast-cocultured monocytes modeled the phenotype of RA synovial macrophage cluster 1 (C1, also termed HBEGF+ or IL1B+ macrophages) (Kuo et al., 2019; Zhang et al., 2023; Zhang et al., 2019), we next tested whether (TNF+PGE2)-stimulated monocytes expressed the defining genes of cluster 1 (128 genes, as defined in Kuo et al., 2019). Here, TNF is linked to rheumatoid arthritis.