Interaction of murine granulocyte-macrophage progenitors and supporting stroma involves a recognition mechanism with galactosyl and mannosyl specificities.

To study the molecular basis of "homing" of granulocyte-macrophage progenitors (CFU-C), we synthesized probes by covalent linking of sugars to bovine serum albumin. Long-term marrow cultures were established in the presence and absence of these probes. In the presence of galactosyl and mannosyl probes, total cell and CFU-C production in the supernate as well as the adherent layer were halted, and cobblestones (representing CFU-C bound to stroma) disappeared. Fucosyl probe and diffusible sugars had no effect on these parameters. These studies suggested membrane lectins with specificity for galactosyl and mannosyl residues may be responsible for the binding of CFU-C to supporting stroma. To determine if CFU-C possesses homing receptors with these specificities, we induced agglutination in marrow cell suspensions with these neoglycoprotein probes. Selective agglutination was observed only by galactosyl and mannosyl probes. The results suggest that CFU-C homing receptors are membrane lectins with specificity for galactosyl and mannosyl residues.