Colony forming activity, density distribution and morphological features of the stem cell population in primary myelofibrosis.

In four patients with untreated primary myelofibrosis, the peripheral-blood cell growth in agar culture (frequency of clusters and colonies) was studied. As cell sources, were used either the buffy coat or the fractions obtained from an albumin discontinuous density gradient, prepared according to Dicke's technique. Besides the agar culture, also morphological features of the blasts of the granulocytic cell series of the gradient fractions were investigated, in order to relate the above-mentioned cell parameters. The results, taken as a whole, pointed out: a) increase in circulating CFUc's (expressed as the number/10(5) nucleated cells) in the patients, when compared to the controls; b) high percentage of CFUc's with an abnormal specific density (below 1.062 in 3 out of 4 patients); c) presence in 3 out of 4 patients, of two populations of blasts: one showing low specific density, small size, high N/C rate, high plating efficiency and no nucleoli; the other with a higher specific density and low plating efficiency, showing the typical morphological features of the myeloblasts.