Neutralization and immunoaffinity chromatography of erythroid colony-stimulating activity in mouse plasma by an anti-erythropoietin monoclonal antibody.

A relationship between erythropoietin (EPO) and erythroid colony-stimulating activity (ECSA) in mouse plasma was examined in fetal mouse liver cell (FMLC) cultures using a monoclonal antibody (MoAb) R2 raised against recombinant human EPO. Most of the ECSA in plasma from normal, anemic, and hypoxic mice was neutralized by MoAb. This neutralization could be reversed by addition of excess of anemic plasma or by preincubation of MoAb with goat anti-mouse IgG antibody. Most of the plasma ECSA was bound to an immunoadsorbent column containing the immobilized MoAb, and the retained ECSA was completely neutralized by MoAb. The plasma ECSA and standard EPO showed parallel dose-response curves and additive effect on CFU-E stimulation. Based on these findings, we conclude that mouse plasma ECSA detected by CFU-E assay using FMLCs is mainly due to EPO.