AXL and rheumatoid arthritis: Serum concentrations of the endogenous ligand of AXL; GAS6, and its decoy receptor soluble AXL (sAXL) which is an inhibitor of the cellular AXL/SOCSs pathway, were measured in RA patient groups: naive-to-treatment (n=20), resistant-to-treatment (n=20), in remission (n=10), and in patients with osteoarthritis (n=10) and age-matched healthy donors (n=10).