Myeloid differentiation in cultures of human hemopoietic precursor cells

Thymidine-dependent effect of granulocyte-derived inhibitor on granulocyte-macrophage progenitor cells (GM-CFC)

We have compared the effect of granulocyte extract (GRE) on proliferation of hemopoietic cells from various sources, using two different cultures media, CMRL 1066 and McCoy 5A. GRE caused a strong (80-90%) inhibition of granulocyte-macrophage colony forming cells (GM-CFC) in cultures with medium CMRL 1066. GM-CFC in human blood and human and mouse bone marrow were equally sensitive to the inhibitor. The inhibitor had a maximal effect in the concentration range corresponding to GRE from 2 x 10(5) to 2 x 10(6) cells per 1 ml culture dish. At higher GRE concentration the inhibition was reduced. GM-CFC from human blood and mouse marrow were suppressed in cultures with McCoy's medium as well, but to a lesser extent than in CMRL 1066 cultures. On the other hand, in cultures with human bone marrow cells (BMC) and McCoy's medium, GRE had no inhibitory effect. CMRL 1066 medium contains a number of components not present in McCoy's medium. In a systematic study where these substances were added one by one to McCoy's medium we found that inhibition by GRE depended upon the presence of thymidine. At a thymidine concentration of 3 x 10(-5) mol/l GRE strongly suppressed GM-CFC in human blood and bone marrow. This thymidine concentration itself had no effect. Other nucleosides or components of the CMRL 1066 did not potentiate the suppressive effect of GRE.

Colony growth characteristics in chronic myelomonocytic leukemia

Using cell culture studies specific in-vitro characteristics have been reported for Philadelphia chromosome positive myelogenous leukemia (Ph+ CML) and for juvenile chronic myelogenous leukemia (JCML) previously. We performed cell culture studies in four patients with chronic myelomonocytic leukemia (CMML) and demonstrated the following in-vitro features: excessively increased circulating CFU-C, while BFU-E and CFU-mix were either moderately increased or not detectable; CFU-C colony formation from CMML mononuclear cells (MNC) without addition of exogenous colony stimulating activity (CSA), even after depletion from adherent cells; failing inhibition of CMML MNC on normal BFU-E colony formation. These in-vitro characteristics point to CMML as a distinct entity. In two CMML-patients investigated CFU-C proliferation appeared to some extent inhibited by the addition of IFN-alpha, IFN-gamma and TNF-alpha to cell cultures.

Autologous transplantation with circulating hemopoietic stem cells

Circulating stem cells exist in sufficient numbers in mouse, dog, and man to allow collection and transplantation after ablative treatment. Preclinical studies in the mouse have shown a low concentration, with a transplantation potential ratio of bone marrow to blood of 1:100. The ratio of circulating stem cells to bone marrow stem cells is more favorable in the dog (1:10-20). Recent pilot studies carried out in different centers with 10 patients have shown that this approach is feasible in man, too. It appears that 5 X 10(8) mononuclear cells/kg of body weight collected by seven or eight leukapheresis procedures of about 4 hrs each is sufficient for fast hemopoietic recovery after marrow ablative treatment. Potential advantages of the use of blood stem cells over bone marrow stem cells are the decreased likelihood of contamination with malignant cells, the avoidance of general anesthesia, and the infusion of immunocompetent cells, which might hasten immunorecovery in the autologous setting.