Erythropoietic colonies in a serum-free system: results in primary proliferative polycythaemia and thrombocythaemia.

The formation of erythropoietic colonies from the peripheral blood of normal subjects, patients with primary proliferative polycythaemia (PPP) and primary thrombocythaemia (PT) was studied, using a chemically defined serum-free (S-) medium. Colony formation was markedly more prominent in the presence of burst-promoting activity (BPA) and erythropoietin (Ep) than with medium alone (P less than 0.001). In cultures using medium alone, significantly more PPP patients formed colonies than the control group (P less than 0.05). In the PT group this difference did not achieve statistical significance, but the mean BFU-E yield was significantly greater than in controls (P less than 0.05). In a separate series of experiments, parallel cultures in serum-containing (S+) and serum-free (S-) systems, in the presence of BPA and Ep did not show any significant difference in colony yield. The growth of 'endogenous' colonies in cultures with serum-free medium alone could be due to a peculiar sensitivity of erythropoietic progenitors to growth factors other than Ep.