Spontaneous formation of megakaryocyte progenitors (CFU-MK) in primary thrombocythaemia.

An improved plasma clot culture method for CFU megakaryocytes (MK) has been developed with a higher plating efficiency and easier identification and enumeration of MK colonies by an indirect immunoperoxidase staining using a monoclonal antibody specific to the platelet glycoprotein IIb/IIIa complex. This technique has been used to study megakaryocytopoiesis in 20 normal individuals, 4 recently diagnosed patients with untreated primary thrombocythaemia (PT) and 2 patients with secondary thrombocytosis (ST). An increased number of MK colonies was evident in peripheral blood (mean 115 +/- 31 CFU-MK/5 X 10(5) seeded cells or 206 +/- 91/ml) and to a lesser extent in bone marrow (mean 188 +/- 26 CFU-MK/5 X 10(5) seeded cells or 696 +/- 103/ml) of PT patients as compared to controls (mean 11 +/- 4/5 X 10(5) seeded cells or 13 +/- 3/ml of peripheral blood and 153 +/- 15/5 X 10(5) seeded cells or 319 +/- 43/ml of bone marrow). There was a very obvious difference between PT patients and the others (controls plus ST patients) because CFU-MK growth with no added stimulus (PHA-LCM or PHA-LCM and normal serum) could be seen in PT patients only.