GLUCAN RECEPTOR AND ZYMOSAN-INDUCED LYSOSOMAL-ENZYME SECRETION IN MACROPHAGES

A receptor for beta-glucan was in the present study shown to mediate b inding of zymosan particles to resident mouse peritoneal macrophages. Lysosomal enzyme secretion in response to zymosan was maximal at a low particle/cell ratio, continuous for at least 3 h after particle/cell contact and inhibitable by soluble glucan. Latex particles of various size caused no selective secretory response, but at high particle/cell ratios were toxic. By use of a fluorescent ligand, the macrophage bet a-glucan receptor was shown to be trypsin-sensitive, Ca2+/Mg2+-indepen dent, recirculating and also present in an intracellular mobilizable p ool. Binding of ligand to the beta-glucan receptor and inhibition of t he lysosomal secretory response to zymosan were both more efficient wi th glucans of larger size, indicating that clustering of glucan recept ors at the cell surface occurs. Such clustering could stabilize ligand binding by multiple interactions and possibly trigger intracellular s ignalling events on binding of zymosan particles.