Polyploid MKs have several centrioles. CD34⁺ cells purified from blood cytapheresis or bone marrow were grown in the presence of PEG-rhuMGDF and SCF or PEG-rhuMGDF alone. At day 8, cells were recovered, cytocentrifuged, fixed, and permeabilized. Cells were double-labeled by indirect immunofluorescence and the DNA was counterstained by the Hoechst dye. Cells were examined with a conventional fluorescence microscope (a and b) and by confocal microscopy (c). (a) Observation with a combination of filters permitting simultaneous visualization of FITC and Hoechst staining. Labeling with an MK-specific antibody directed toward vWF (FITC) shows a granular pattern. Original magnification × 1,000. (b) Centrioles appear as red spots (TRITC) in the cytoplasm. These spots (∼16) appear to be clustered in the Golgi area of this MK. (c) Centrioles (red) are better observed by a confocal microscopy and can be seen to be scattered in the cytoplasm of the MK. Original magnification × 2,000.