Specific binding of lipopolysaccharides to mouse macrophages--I. Characteristics of the interaction and inefficiency of the polysaccharide region.

Tritium-labeled lipopolysaccharide interacted specifically and reversibly with mouse peritoneal macrophages. The binding was higher at 22 degrees C than at 4 degrees C, but was no longer observable at 37 degrees C. The specificity of the interaction (inhibition with unlabeled LPS) was strictly dependent on the presence of serum, and required divalent cations. The binding was saturable. The specific binding sites of peritoneal macrophages were saturated with 6-9 x 10(6) LPS molecules/cell, and those of macrophage-like cell lines with 2-3 x 10(6) molecules/cell. The binding of LPS was not inhibited by ligands of scavenger receptors (maleylated BSA) or complement receptors (zymosan), but was strongly inhibited with dexamethasone, a glucocorticoid which is known to modulate the expression of other surface markers of macrophages. The polysaccharide region of the LPS, as well as 3-deoxy-2-octulosonic acid (KDO) coupled to bovine serum albumin, did not bind to macrophages, whereas a specific binding was observed with a lipid A-BSA conjugate.