Identification of young megakaryocytes by immunofluorescence and cytophotometry

The DNA-content of fluoresceine-labeled platelet antigen containing cells of mouse bone marrow was measured. For immunofluorescence highly specific anti-mouse-platelet-serum and fluoresceine-conjugated antigammaglobuline was used, applying the "sandwich" technique. Three hundred panoptically identifable megakaryocytes served as control group. The DNA-polyploidization pattern of megakaryocytes and immunofluorescence positive cells was almost identical. However, among the immunofluorescence positive cells a considerable amount of cells showed DNA-values lower than 4c, whereas the megakaryocytes of the Pappenheim stained smears revealed no DNA-values lower than 4c. The percentages of diploid and tetraploid cells, respectively, was 6 and 7% compared with 0 and 1% of panoptically identifiable megakaryoctyes. The results suggest that young megakaryocytic cells with diploid and tetraploid DNA-values can be detected by immunofluorescence technique, indicating that the flow from the uncommited to the committed megakaryocytic precursor cell appears at this early stage of megakaryocyte production.