Analysis of different glycosylation states in IgG subclasses

Altered IgG glycosylation affects certain immunological activities of human IgG. Enzyme-linked lectin assays (ELLA) were developed for detecting the glycosylation on IgG and its individual subclasses in sera from healthy controls. Biotinylated Sambucus nigra, Ricinus communis agglutinin I and Bandeiraea simplicifolia II were used to detect the terminal sialic acid (SA), galactose (Gal) and N-acetylglucosamine (GlcNAc) sugar residues, respectively on the captured IgG. A mild oxidation step of the anti-IgG-coated plates obviated background reaction with the lectins. Terminal glycosylation varied significantly with age. The old age group (> 65 years) had less SA in IgG1, and IgG2, when compared to young (0-19 years) and adult (20-39 years) groups, respectively. Also the old age group had less Gal in IgG2, IgG3 and IgG4 subclasses compared to the adult group, and to the young group in the case of IgG3. This ELLA system may be a valuable tool in the detection of glycosylation disorders in patients' sera.