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

Background: The α1,3-galactosyltransferase gene-knockout (GalT KO) mice are able to produce natural anti-αGal antibodies apparently without any specific immunization. GalT KO mice are commonly used as a model immunological system for studying anti-αGal responses to Gal-positive xenografts in human. In this study, we compared the specificity of mouse and human αGal antibodies to realize the adequacy of the murine model.

Methods: Using hapten-specific affinity chromatography antibodies against Galα1-3Galβ1-4GlcNAcβ 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-Galα 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 Galα1-3Galβ1-4GlcNAcβ 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 α-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.