IN-VITRO SENSITIVITY OF HUMAN ERYTHROID PROGENITORS TO HEMATOPOIETIC GROWTH-FACTORS - STUDIES ON PRIMARY AND SECONDARY POLYCYTHEMIA

Background. Primary proliferative polycythemia is a clonal disease cha racterized by excessive hemopoiesis and associated with a lower than n ormal erytropoietin plasma level; in vitro colony studies may reveal i ncreased sensitivity of the abnormal clone to hemopoietic growth facto rs. Materials and Methods. We studied the in vitro formation of erythr oid colonies (BFU-E derived clone) in cultures set up with a serum-fre e medium and containing Epo, interleukin 3 (IL-3) and stem cell factor (SCF), in various combinations. The clonogenic test was performed by plating non adherent mononuclear cells from the peripheral blood of no rmal subjects and from patients with PPP and secondary polycythemia (S P). Results. SCF is a major amplifier of erythroid colony growth, in t he presence of Epo; in cultures from PPP patients, however, the presen ce of SCP, in addition to Epo, enhances colony formation at about the same rate as in cultures from normal subjects. When SCF is omitted, th e presence of even modest amounts of E,po and IL-3 is sufficient to ob tain a statistically significant difference between colony formation f rom PPP patients on the one side, and SP patients and normal subjects on the other. Conclusions. Our results show that in vitro culture stud ies may contribute an additional diagnostic criterion for distinguishi ng between PPP and SP in uncertain cases. It is also possible that hyp ersensitivity to erythropoietic factors may play a role in the pathoge netic mechanism of primary proliferative polycythemia.