Dominant suppression of inflammation by glycan-hydrolyzed IgG

A unique anti-inflammatory property of IgG, independent of antigen specificity, is described. IgG with modification of the heavy-chain glycan on asparagine 297 by the streptococcal enzyme endo-β- N -acetylglucosaminidase (EndoS) induced a dominant suppression of immune complex (IC)-mediated inflammation, such as arthritis, through destabilization of local ICs by fragment crystallizable–fragment crystallizable (Fc-Fc) interactions. Small amounts (250 µg) of EndoS-hydrolyzed IgG were sufficient to inhibit arthritis in mice and most effective during the formation of ICs in the target tissue. The presence of EndoS-hydrolyzed IgG disrupted larger IC lattice formation both in vitro and in vivo, as visualized with anti-C3b staining. Neither complement binding in vitro nor antigen–antibody binding per se was affected.