α- d -Galactosylation of surface fucoglycoconjugate(s) upon stimulation/activation of murine peritoneal macrophages

Abstract

Murine resident macrophages express, on their surface, carbohydrate epitopes which undergo changes during their stimulation/activation as monitored by binding of 125 I labelled Evonymus europaea and Griffonia simplicifolia I-B 4 lectins. Treatment of the stimulated macrophages with coffee bean α-galactosidase abolished binding of the GS I-B 4 isolectin and changed the binding pattern of the Evonymus lectin. The affinity ( K a ) of Evonymus lectin for α-galactosidase-treated macrophages decreased approximately 23-fold, from 1.25×10 8 M −1 to 5.5×10 6 M −1 . Subsequent digestion of α-galactosidase-treated macrophages with α- l -fucosidase from Trichomonas foetus , further reduced binding of Evonymus lectin. Resident macrophages showed the same pattern of Evonymus lectin binding, with the same affinity, as α-galactosidase-treated, stimulated macrophages. These results, together with a consideration of the carbohydrate binding specificity of the Evonymus lectin which, in the absence of α- d -galactosyl groups, requires α- l -fucosyl groups for binding, indicate the presence, on resident macrophages, of glycoconjugates with terminal α- l -fucosyl residues. It is also concluded that during macrophage stimulation/activation α- d -galactosyl residues are added to this glycoconjugate and that they form part of the receptor for Evonymus lectin. The same glycoconjugate(s) is/are also expressed on the activated macrophage IC-21 cell line which exhibits the same characteristics as that of stimulated peritoneal macrophages, i.e., it contains α- d -galactosyl end groups and is resistant to the action of trypsin. Both lectins were also specifically bound to Corynaebacterium parvum activated macrophages.