Immunocytochemical detection of normal and abnormal megakaryocytes using monoclonal antibody to glycoprotein IIb-IIIa (TP80): the quantitative assay in normal and in leukaemic patients.

We identified bone marrow megakaryocytes by an immunocytochemical technique using a monoclonal antibody (TP80) against platelet glycoprotein IIb-IIIa (GPIIb-IIIa). The immunocytochemical technique using TP80, specific to megakaryocytes, enabled us to observe cellular morphology and immunological reaction under light microscopy, and permitted quantitative assessment of megakaryocytes. In normal marrow, TP80 labelled 22 +/- 5 megakaryocytes/10(4) mononuclear cells (mean +/- 1 SD, n = 14). In addition to typical large megakaryocytes, small immature megakaryocytes (less than or equal to 20 micron) were recognized in 10-15% of total megakaryocytes. 4 out of 18 patients with acute myeloblastic leukaemia and 9 of 10 patients with myelodysplastic syndrome showed increased numbers of megakaryocytes. In these patients, cell size distribution was abnormal, i.e., most of the megakaryocytes consisted of small, atypical megakaryocytes. None of the patients with acute lymphoblastic leukaemia showed increased megakaryocytes. Immunocytochemical identification of megakaryocytes using a specific antibody is useful to quantitate the megakaryocytes and to detect the proliferation of atypical megakaryocytes in several leukaemic conditions.