MERTK and rheumatoid arthritis: In human synovial tissue, MerTK+ synovial macrophages are characterized by a specific regulatory signature depending on the disease state (healthy, active RA, or remission): in particular, RA patients who underwent remission show the upregulation of the genes encoding for the transcription factors Krüppel-like factor 2 (KLF2), KLF4, nuclear receptor subfamily 4 group A member 1 (NR4A1), NR4A2, or the dual-specificity phosphatase1 (DUSP1), representing negative regulators of inflammation that actively participate to restore tissue homeostasis, through lipid mediators such as resolvins (64).