Solid phase measurements of antibody and lectin binding to xenogenic carbohydrate antigens

Objectives: In future pig-to-man xenotransplantation it is important to master tools that identify potentially xenogenic αgalactose (Galα) antigens in the doner tissue. Design and methods: We have measured the binding potentials of Galα detecting lectins and antibodies, including a naturally occurring subfraction from human serum, to Galα containing neoglycoproteins and mouse laminin that were immobilized on microtiter plates. Results: Galα reactive antibodies with similar monosaccharide specificity have distinct structural preference for sugar ligands. Laminin and neoglycoproteins were treated with α-galactosidase and subsequently incubated with antibodies and lectins. The enzyme treatment was more deleterious on antibody binding than on lectin binding. Conclusion: Antibodies and lectins may bind to different galactose determinants on the glycoproteins. Two anti-Galα1 antibodies that both have been raised against glycans on rabbit red blood cells may recognize Galα-antigens with varying specificities. Binding results obtained after digestion with α-galactosidase indicate that some xenoreactive Galα groups are not directly accessible for removal by the enzyme.