Specific ligation of surface α‐D‐galactosyl epitopes markedly affects the quantity of four major proteins secreted by macrophages

Activated macrophages (Mφs) have terminal α‐D‐galactosyl (αD‐Gal) residues on their membranes that are not apparent on resting cells. Ligation of these epitopes with Griffonia simplicifolia I‐B 4 (GSI‐B 4 ), a lectin that has specificity for α‐D‐Gal residues, alters selected Mφ functions. To explore the mechanism(s) that may be responsible for some of the functional changes, alterations in the secretory pattern of [ 35 S]methionine‐labeled proteins were assessed when cells were cultured with or without this ligand. The proteins were identified by Western blots and quantitated. Interestingly, α‐D‐Gal ligation proved to decrease the secretion of some proteins while increasing the secretion of others. Some of the most significant changes were observed in four proteins: fibronectin and transglutaminase were down‐regulated by 55 and 66% respectively, while plasminogen activator inhibitor type 2 was increased by 259% and collagenase was increased 1000‐fold. These observations show that the emergence of new oligosaccharide epitopes, such as α‐D‐Gal, concomitant with Mφ activation may serve to mediate the transduction of signals that cause quantitative changes in the elaboration of diverse Mφ products. The biologic significance of the four identified proteins has been well established. Fluctuations in their levels are likely to play a role at sites of chronic inflammation.