STRUCTURAL-CHANGES IN THE OLIGOSACCHARIDE MOIETY OF HUMAN-IGG WITH AGING

In order to elucidate the relationship between glycosylation of IgG an d aging, oligosaccharide structures of human IgG purified from sera of men and women aged 18 to 73 years were investigated. Oligosaccharides were liberated quantitatively from IgG by hydrazinolysis followed by N-acetylation and were tagged with p-aminobenzoic acid ethyl ester. Th e oligosaccharide structures were then analyzed by HPLC in conjunction with sequential exoglycosidase digestion. All IgG samples were shown to contain a series of biantennary complex type oligosaccharides which consisted of +/-Gal beta 1-4GlcNAc beta 1-2Man alpha 1-6(+/-GlcNAc be ta 1-4)(+/-Gal beta 1-4GlcNAc beta 1-2Man alpha 1-3)Man beta 1-4GlcNAc beta 1-4(+/-Fuc alpha 1-6)GlcNAc and their mono- and disialo glycofor ms in different ratios. In female IgG samples only, the incidence of n on-galactosylated oligosaccharides with non-reducing terminal GlcNAc r esidues increased with aging (r > 0.8), whereas that of digalactosylat ed oligosaccharides decreased (r < -0.8). A weaker correlation was obs erved between aging and the incidence of neutral and monosialo oligosa ccharides in female IgG (r = 0.461 and r = -0.538, respectively) and b etween aging and the incidence of oligosaccharides with a bisecting Gl cNAc in both male and female IgG samples (r = 0.566 and r = 0.440, res pectively). In addition, a significant change with aging in the galact osylation of IgG oligosaccharides was observed in females in their thi rties, fifties, and sixties (p < 0.02, p < 0.01, and p < 0.04, respect ively). These findings may contribute to our understanding of autoimmu ne diseases such as rheumatoid arthritis in which glycosylation is inv olved.