Electron microscopic identification of hemopoietic progenitor cells by exploiting their sugar-recognizing receptors using a newly developed minibead technique.

To identify hemopoietic progenitor cells in electron microscopic preparations we exploited the presence of "homing receptors" with galactosyl, mannosyl, and fucosyl specificities on their membrane surfaces. Amide-modified latex minibeads were covalently linked to the para-aminophenyl derivative of galactose, mannose, and fucose in pyranose form. Incubation of these probes with murine bone marrow cells led to specific binding of probes to a small proportion of marrow cells, comprising 0.5%, 0.6%, and 0.4% of the mononuclear marrow cell population, respectively, for galactosyl, mannosyl, and fucosyl probes. Specificity of the binding was demonstrated by inhibition in the presence of excess soluble sugars. The cells binding the probes were small, 4-5 microns, with characteristics similar to those described for progenitor cells. The implications of this technique for purification of hemopoietic progenitor cells are discussed.