MERTK and rheumatoid arthritis: Interestingly, the main macrophage population we found in control capsule is phenotypically similar (LYVE1 and MERTK expressing [SI Appendix, Fig. S3B]) to those found in rheumatoid arthritis patients under remission that were shown to be negative regulators of inflammation and induced repair responses in synovial fibroblasts in vitro (52).