CD47 and pancreatic insulinoma: Consistently, in a separate experiment, we also observed that insulinoma cell function in a syngeneic model depends on SIRPα-mediated inhibition of macrophages through engagement with its ligand CD47, i.e., treatment with anti-SIRPα Abs enhanced macrophage-mediated elimination of mouse insulinoma cells in diabetic Rag2−/− γ chain−/− mice (data not shown).