Studies on two biological phenomena in in vitro cell cultures: the reversibility of leukemic blast cells and the immunologic enhancement of tumor growth.

: The nature of the leukemic process is discussed with respect to the possible in vitro transformation of the leukemic blast cells into myeloid differentiated cells. During the period 1968-1970 we noticed this process in bone marrow cultures in fluid medium. The differentiation was established on morphologic and cytochemical criteria; the proportion of mature cells or those undergoing maturation with peroxidase positive reaction increased over 50% reaching even 70-80%. Our recent observations can be discussed from several points of view but leukemic blast cell reversibility is now a phenomenon with therapeutical applications. The phenomenon of malignant cells growth enhancement has been considered as an antibody mediated immune process. In a previous paper we have demonstrated in AKR mice the possibility of achieving the growth enhancement of lymphoblastic cells in mixed cultures with normal autologous or isologous splenic cells. Other investigations have been carried out by means of mixed cultures in human leukemias and malignant lymphomas. The intensity of blast-cell proliferation was followed up by comparing the number of colonies and TH3 incorporation in simple cultures with those in mixed cultures. The observations made in the 20 culture systems followed-up over 3-5 and 8-10 days proved the "malignant cell growth enhancement" by the immune mononuclear cells (lymphocytes and macrophages).