Proliferation in liquid culture of megakaryocytes from the blood of patients with primary myelofibrosis and other myeloproliferative disorders.

Using a short term liquid system we have shown that blood from some patients with primary myelofibrosis (PMF) and chronic granulocytic leukaemia (CGL) in megakaryoblastic transformation (CGL-Mk) gives rise to large numbers of progenitor cells committed to the megakaryocyte (Mk) lineage. As assessed by indirect immunofluorescence the number of cells reacting with three antiplatelet monoclonal antibodies, C17, J15 and AN51, increases during the culture period. There is no equivalent increase in cultures from the blood of normal individuals or patients with essential thrombocythaemia (ET). Furthermore plasma-free supernatants from cultures of the cells from patients with PMF and CGL-Mk stimulate the rate of proliferation of fibroblasts from normal bone marrow. These data provide further evidence for the involvement of the Mk lineage in PMF and CGL and suggest that the excess fibrosis seen in these conditions may be caused by a factor emanating from Mks.