PROLIFERATIVE AND DIFFERENTIATIVE POTENTIAL OF THROMBOPOIETIN-RESPONSIVE PRECURSORS - EXPRESSION OF MEGAKARYOCYTIC AND ERYTHROID LINEAGES

We investigated changes in proliferative potential and surface markers during human megakaryocytic differentiation, using megakaryocytic cel ls grown by thrombopoietin (TPO). Cells grown in response to TPO from CD34(+) cord blood cells in a liquid culture system expressed CD41b at a frequency of 92% and CD42b at a frequency of 80% on day 10, whereas cells expressing other lineage markers constituted less than 2.5% of this population The cultured cells were divided into CD41b(-)/CD42b(-) , CD41b(+)/CD42b(-), and CD41b(+)/CD42b(+) cells. Comparison of their respective proliferative potentials showed that CD41b(-)/CD42b(-) cell s generated megakaryocytic: progeny in response to TPO to a lesser ext ent, but responded ro the combination of growth factors (GFs) more int ensely than CD41b(+)/CD42b(-) cells. Almost all CD41b(+)/CD42b(+) cell s failed to undergo cell division. In the culture containing GFs, some CD41b(-)/CD42b(-) cells and CD41b(+)/CD42b(-) cells gave rise to eryt hroid as well as megakaryocytic progeny. The potential of these cells to yield erythroid progeny in response to GFs correlated well with the ir expression of CD34. These results suggest that TPO generates precur sors with a potential to differentiate into megakaryocytic and erythro id lineages.