Characteristics of megakaryocyte colony formation in normal individuals and in primary thrombocythemia: studies using an optimal cloning system.

Colony formation by megakaryocyte (MK) progenitors was studied in 36 normal individuals and in 26 patients with primary thrombocythemia (PT) using an improved plasma clot cloning system. MK colonies were identified by immunoperoxidase staining using a monoclonal antibody against human platelet glycoprotein IIb/IIIa complex. In normal individuals, a frequency of 194 +/- 23 MK colony-forming units (CFU-MK) per 5 X 10(5) bone marrow nonadherent mononuclear cells and 11 +/- 4 CFU-MK per 5 X 10(5) blood mononuclear cells was found. These CFU-MK grew as large (greater than 20 cells), mean (11-20 cells), small (3-10 cells), or mix-MK colonies (at least two MK) that comprised 15%, 23%, 62%, or 5% of all MK colonies in bone marrow and 0%, 8%, 92%, or 1% in peripheral blood, respectively. In PT, several abnormalities of MK colony formation were observed: 1) increased circulating CFU-MK numbers, 2) increased mix-MK colony formation, 3) spontaneous MK colony formation without phytohemagglutinin-stimulated leukocyte-conditioned medium and normal serum, 4) decreased proportion of larger MK colonies (greater than 11 cells) in PT bone marrow, and 5) failure of PT plasma or serum to stimulate MK colony formation by normal marrow cells in a normal fashion. These results indicate some of the characteristics of quantitative and qualitative abnormalities of in vitro megakaryocytopoiesis in PT.