Single-cell (sc) RNA-sequencing (RNA-seq) analysis of synovial tissue suggested that high expression of MerTK characterised non-inflammatory arthritis macrophages (e.g., osteoarthritis)9 and, when co-expressed with CD206, MerTK identified a subset of synovial macrophages more abundant in healthy joints and RA patients in remission10. This evidence concerns the gene MERTK and rheumatoid arthritis.