The present protocol is aimed to determine the natural anti-carbohydrate antibody repertoire (binding specificities) of alphaGal-KO mice. Glycochips (microchips printed with 577 different carbohydrate structures) were printed by Semiotik LLC (Moscow, Russia) using a collection of different amine-functionalized glycans and bacterial polysaccharides covalently coupled to N-hydroxysuccinimide-derivatized glass slides (slide H, Schott-Nexterion, Mainz, Germany). The glycan library included blood group antigens and some of the most frequently occurring terminal oligosaccharides, as well as core motifs of mammalian N- and O-linked glycoproteins and glycolipids, tumor-associated carbohydrate antigens, and polysaccharides from pathogenic bacteria with fully characterized structures (Zelinsky Institute of Organic chemistry, Moscow, Russia).