Proliferation of haematopoietic colonies in serum-free cultures

In eight patients with polycythaemia vera and 20 normals, mononuclear cells of the peripheral blood were cultured in methylcellulose with and without exogenously added erythropoietin. The cultures were set up with fetal calf serum and with a serum-free medium of unsaturated fatty acids, lecithin and cholesterol. In patients with polycythemia vera, we found a proliferation of haematopoietic colonies without erythropoietin in both culture systems which could not be seen in normals. The proliferation of endogenous colonies in serum-free media suggests that polycythaemia vera is a clonal disorder which can be modulated by serum factors and by erythropoietin.