The physicochemical properties of erythrocyte derived activity which enhances murine bone marrow colony growth in agar culture.

A stable preparation which retains enhancement activity for the growth of murine granulocyte-macrophage colonies in agar culture has been extracted from human and rat erythrocytes by osmotic lysis and high speed centrifugation. Trypsin digestion followed by Sephadex G-25 column chromatography has resulted in the removal of haemoglobin and the isolation of an active fraction with an apparent molecular weight of 900 to 1000 daltons. Enhancement activity was abolished by n-ethylmaleimide (NEM) treatment, suggesting that the enhancement is dependent on the presence of free sulphydryl groups.