Interferon α/β is required for production of soluble Axl, and combining M2c polarizing conditions with type I interferon exposure inhibits soluble Mer production and enhances soluble Axl release. Levels of soluble Mer (sMer) (A), soluble CD163 (sCD163) (B) and soluble Axl (sAxl) (C) were measured in supernatants of monocytes/macrophages cultured for 3 days in the presence or absence of type I interferons (IFN-α or IFN-β), macrophage growth factors (macrophage colony-stimulating factor (M-CSF) or granulocyte macrophage colony-stimulating factor (GM-CSF)), M2c polarizing agents (interleukin 10 (IL-10) or dexamethasone) or combinations of these. On day 2, low doses of lipopolysaccharide (LPS) were added for an additional 24 hours to stimulate ectodomain shedding of membrane receptors. Surface expression levels of Mer receptor tyrosine kinase (MerTK), Axl and CD163 were measured by flow cytometry (D). Numbers shown in (D) refer to mean fluorescence intensity values. Data are representative of three independent experiments. Dex, dexamethasone. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.