Chromosome analysis of isolated colony erythroblasts in chronic myelogenous leukaemia.

To isolate and karyotype the progeny of erythroid progenitors, we applied colony erythroblasts derived from plasma clot marrow cultures from two healthy adults and two patients with newly diagnosed Ph1+ chronic myelogenous leukaemia (CML) to discontinuous Stractan density gradients. Erythroid colony proliferation by patient cells was increased relative to that of normal donor cells (P less than 0.01). 'Endogenous' colonies appeared in patient but not in normal donor marrow cultures. Greater than 95% of nucleated cells equilibrating at rho greater than or equal to 1.071 were basophilic proerythroblasts. While analysis of chromosome spreads of normal donor cells in this fraction showed normal karyotypes, cells from patient marrow cultures were Ph1+, whether cultured in the presence or absence of added erythropoietin. These findings suggest that chromosome abnormalities of erythroid progenitors may be expressed by their progeny in tissue culture, and that Stractan may be a useful supporting medium for separating colony erythroblasts for chromosome analysis.