Cytoenzymological-cytogenetical correlations concerning chronic granulocytic leukemia leucocytes.

By means of histochemical demonstration of dihydrofolate reductase activity and chromosomal analysis, peripheral white blood cells from patients with chronic granulocytic leukemia were studied in vitro cultures grown on normal leucocytes feeder-layers. After 14 days of incubation, two different types of colonies were found corresponding to the leukemic and normal leucocytic populations: (a) made up of Ph'-positive leucocytes which have a high dihydrofolate reductase activity; (b) made up of Ph'-negative leucocytes, slightly positive for dihydrofolate reductase activity.