Analysis of haemopoiesis: the use of cell markers and in vitro culture techniques in studies of clonal haemopathies in man.

The clonal haemopathies have in common the expansion of a neoplastic stem cell which has retained a variable capacity for differentiation to granulocytes, monocytes, erythrocytes, and platelets. Although normal stem cells are present in such patients, their differentiation is somehow suppressed. However, their presence may be demonstrated either by cell culture studies, employing G6PD as the marker in appropriately selected cases, or by their emergence in patients subjected to marrow ablative chemotherapy. Suppression of normal stem cell growth and development does not require a hyperproliferative marrow, and the current data do not support the notion that normal stem cells are simply reduced in frequency by a vast increase in the numbers of neoplastic progenitors. It is likely, therefore, that such suppression involves cellular signals, operating over short distances (perhaps through cell-to-cell contact), which interfere with normal progenitors. Thus, stem cell culture techniques, in combination with cell markers, have provided a direct and informative way to approach the issues of disease pathogenesis, the kinetics of stem cell differentiation, and the interaction of normal and neoplastic cells in patients with clonal haemopathies.