Conditioned media prepared from human lung, placenta, peripheral leukocytes, cultured human pancreatic carcinoma cells, and cultured cervical carcinoma cells exhibit a common pattern of two distinct colony-stimulating factors (CSF) separable by isoelectrofocusing. Type I CSF appears polydisperse on isoelectrofocusing, showing multiple peaks with an isoelectric point of 3.6-4.7 and mol wt 50,000. It has a much higher activity in mouse than in human bone marrow, and stimulates the formation of predominately macrophage colonies. Type II CSF has an isoelectric point of 5.7 and mol wt 27,000 and exhibits higher activity in human than in mouse marrow, yielding predominately granulocytic colonies.
M C Wu, A A Yunis