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

In future pig-to-man xenotransplantation it is important to master tools that identify potentially xenogenic alphagalactose (Galalpha) antigens in the doner tissue.

We have measured the binding potentials of Galalpha detecting lectins and antibodies, including a naturally occurring subfraction from human serum, to Galalpha containing neoglycoproteins and mouse laminin that were immobilized on microtiter plates.

Galalpha reactive antibodies with similar monosaccharide specificity have distinct structural preference for sugar ligands. Laminin and neoglycoproteins were treated with alpha-galactosidase and subsequently incubated with antibodies and lectins. The enzyme treatment was more deleterious on antibody binding than on lectin binding.

Antibodies and lectins may bind to different galactose determinants on the glycoproteins. Two anti-Galalpha1 antibodies that both have been raised against glycans on rabbit red blood cells may recognize Galalpha-antigens with varying specificities. Binding results obtained after digestion with alpha-galactosidase indicate that some xenoreactive Galalpha groups are not directly accessible for removal by the enzyme.