Degranulation of polymorphonuclear leukocytes is induced by multivalent cross-linking of wheat germ agglutinin binding site(s) on cell membrane.

Polymorphonuclear leukocyte (PMN) surface membrane glycoproteins very likely are involved in the phenomenon of stimulus-response coupling. Previously, we have shown that subagglutinating concentrations of the plant lectin, wheat germ agglutinin (WGA) specifically and irreversibly inhibited N-formyl-methionyl-leucyl-phenyl-alanine (FMLP)-mediated PMN chemotaxis. WGA did not affect the binding of [3H]FMLP to its receptor on the PMN plasma membrane. We have examined the possibility that cross-linking of WGA binding sites may elicit PMN degranulation. We have found that multivalent, but not bivalent, cross-linking of WGA bound to PMNs elicits release of lysosomal constituents. This phenomenon was specific for WGA since it did not occur when concanavalin A (Con A), instead of WGA, was used. It is intriguing to speculate that WGA may attach to a "physiologic" receptor for FMLP on the PMN membrane and that redistribution (cross-linking) of this receptor might be an early event in the activation of PMNs by FMLP.