Specificity profile of αGal antibodies in αGalT KO mice as probed with comprehensive printed glycan array: Comparison with human anti-Galili antibodies

Background: The alpha 1,3-galactosyltransferase gene-knockout (GalT KO) mice are able to produce natural anti-alpha Gal antibodies apparently without any specific immunization. GalT KO mice are commonly used as a model immunological system for studying anti-alpha Gal responses to Gal-positive xenografts in human. In this study, we compared the specificity of mouse and human alpha Gal antibodies to realize the adequacy of the murine model. Methods: Using hapten-specific affinity chromatography antibodies against Gal alpha 1-3Gal beta 1-4GlcNAc beta epitope were isolated from both human and GalT KO mice blood sera. Specificity of isolated antibodies was determined using a printed glycan array (PGA) containing 400 mammalian glycans and 200 bacterial polysaccharides. Results: The quantity of isolated specific anti-Gal alpha antibodies corresponds to a content of <0.2% of total Ig, which is an order of magnitude lower than that generally assumed for both human and murine peripheral blood immunoglobulin, with a high predominance of IgM over IgG (95% vs 5%). Analysis using a printed glycan array has demonstrated that (a) antibodies from both species bind not only the Gal alpha 1-3Gal beta 1-4GlcNAc beta epitope, but also unrelated glycans; (b) particularly, for human (but not mouse) antibodies the best binders appear to be bacterial polysaccharides; (c) the profile of mouse antibodies is broader, it is noteworthy that they recognize a variety of human blood group B epitopes and even glycans without the alpha-galactosyl residue. Conclusions: We believe that the mouse model should be used cautiously in xenotransplantation experiments when the fine epitope specificity of antibodies is critical.

Automated summary

The study compared the specificity of alpha-Gal antibodies in mice and humans, finding that the mouse model recognizes a broader range of human blood group B epitopes and glycans without the alpha-galactosyl residue compared to human antibodies, which show a preference for binding bacterial polysaccharides. This suggests caution should be exercised in using the mouse model in xenotransplantation experiments when epitope specificity is critical.