Measured by its ability to promote the expansion of E16 rat liver mononuclear cells in vitro, in the presence of Recombinant Mouse SCF/c-kit Ligand, Recombinant Mouse Thrombopoietin/Tpo, and Recombinant Mouse Flt-3 Ligand. The ED50 for this effect is 50-200 ng/mL in the presence of a cross-linking antibody, Mouse Anti-polyHistidine Monoclonal Antibody.