Analysis of 51 synovial tissue samples from patients with RA or OA identified 18 unique cell populations, including T cells, B cells, monocytes, and fibroblasts.125 Combining mass cytometry and transcriptomics revealed cell states expanded in RA synovia, such as THY1(CD90)+HLA-DRAhi sublining fibroblasts, IL1B+ pro-inflammatory monocytes, ITGAX+TBX21+ autoimmune-associated B cells, as well as PDCD+ peripheral helper T (T(PH)) cells and follicular helper T [T(FH)] cells. Here, ITGAX is linked to rheumatoid arthritis.