Biological significance of carbohydrate chains on monoclonal antibodies

We have prepared monoclonal hapten-specific mouse IgG2b antibodies depleted of asparagine-linked carbohydrate chains by treating the hybridoma cells with tunicamycin. The carbohydrate-deficient antibodies behaved in an identical manner to the normal antibodies wth regard to fine antigen-binding reactivity (a Fab fragment feature) and protein A binding capacity [a feature requiring integrity of the C(H)2 and C(H)3 domain-interaction regions in the constant region of the heavy chain (C(H))]. However, they lost the ability to activate complement, to bind to Fc receptors on macrophages, and to induce antibody-dependent cellular cytotoxicity. Furthermore, antigen-antibody complexes produced from such carbohydrate-deficient antibodies failed to be eliminated rapidly from the circulation. We conclude that removal of carbohydrate chains from IgG molecules may have a profound and highly select impact on the biological activity to these antibodies.