Investigators performed single-cell transcriptome profiling of disaggregated synovial tissue from five RA patients.118 In this early study, 20 387 single cells were sequenced, revealing 13 transcriptomically distinct clusters, including 10 immune populations that broadly expressed PTPRC (CD45) and three fibroblast populations, expressing uniform high levels of COL1A2. Within immune cells, clear markers of known subtypes, including canonical macrophage markers (MARCO), T cell (CD3), and B-cell (MS4A1) markers, were found. This evidence concerns the gene MARCO and rheumatoid arthritis.