A combination of single-cell and bulk RNA sequencing and mass cytometry have identified 18 functionally distinct cell phenotypes in active RA synovium, of which many-fold expansion was observed for THY1+CD34-HLA-DRAhi sublining fibroblast and IL1B+CD11c+CD14+ pro-inflammatory monocyte populations (64). This evidence concerns the gene CD14 and rheumatoid arthritis.