Inhibition of processing of asparagine-linked carbohydrate chains on IgG2a by using swainsonine has no influence upon antibody effector functions in vitro

Removal of asparagine (Asn)-linked carbohydrate chains from IgG antibody molecules reduces their antibody effector functions such as C activation and FcR binding. We have prepared IgG2a mAb with modified structure of carbohydrate chains by treating the hybridoma cells with swainsonine, which inhibits the processing of Asn-linked carbohydrate chains at the site of action of mannosidase II. These antibodies have obtained the capacity to bind lentil lectin and have become sensitive to endoglycosidase H digestion, indicating the structural changes of oligosaccharides from complex type to hybrid type. They behaved in an identical manner to the normal IgG2a antibodies with regards to extracellular secretion, Ag-binding capacity, C-mediated hemolysis and FcR-mediated functions. Critical moieties of Asn-linked carbohydrate chains on IgG molecules to retain their antibody effector functions were discussed.