A need for hematopoietic stem cells, particularly cells destined to enter the megakaryocyte (MK) series, prompted phenotypic analysis of mononuclear leukocytes in human cord blood. To this end, immunohistochemical, flow cytometric, and ultrastructural techniques were used. The immunogold silver enhancement method (IGS) for the detection of the MK-specific glycoprotein (GP) IIb/IIIa epitopes combined with a monocyte-specific stain for alpha-naphthyl butyrate esterase proved to be superior to flow cytometry (FACS) for precise quantitation of cell types in each sample. Immunoelectron microscopy afforded a description of distinctions between precursors bearing GPIIb/IIIa epitopes and other stem cells of the myeloid series. The number of presumed MK progenitors was surprisingly high, averaging 1.8% +/- 1.3% (range, 0.2% to 4.6%) by IGS and 4.1% +/- 3.0% (range, 0.2% to 9.3%) by FACS analysis. The occurrence of GPIIb/IIIa-positive denuded MK nuclei in cord blood was of interest, but was too small to affect these data. These observations should advocate a greater use of cord blood for restitution of MK/platelet-lineage-depleted patients as well as for experimental studies concerned with MK differentiation.

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Copyright © 1992 by The American Society of Hematology
1992
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