Relation between expression of GPIIb/IIIa, cell size, granularity, and ploidy of human marrow MKs. (A) Distribution of marrow MKs by surface expression of GPIIb/IIIa, cell size as estimated by forward light scatter (FSC), granularity as reflected by 90° light scatter or side scatter (SSC), and DNA content. Note the progressive increase of all parameters in relation to ploidy. (B) (i) The distribution of marrow cells according to membrane-GPIIb/IIIa immunofluorescence and the DNA content. Cells with background fluorescence represent the principal marrow cell population with ploidy classes of 2N and 4N (red). The highly fluorescent cells represent the MK population with polyploid subclasses (blue). (ii) The DNA histogram of the MK population is shown. The modal ploidy is 16N.