On the significance of heterogeneity of plasma glycoproteins possessing N-glycans of the complex type: a perspective

The properties of glycoproteins and, particularly, their range of heterosaccharide moieties (glycans) have become the subject of increasing interest during the past twenty years. Evidence is accumulating, from studies of glycoprotein biosynthesis, which suggests that heterogeneity of glycoproteins is not generally due to a ‘poor preparative technique’ but, rather, is a feature of biosynthesis. In an attempt to explain the significance of heterogeneity, we propose that the events which control biosynthesis are sensitive to extracellular stimuli and, consequently, yield certain ‘acute-phase’ glycoproteins which may contain an altered profile ofN-glycans. The nature and quantity of circulating, protein-bound N-glycans may influence the immune reaction of the host to the stimulus.