IgVH genes encoding xenoantibodies directed at GalTKO xenoantigens in rhesus monkeys

Abstract

Galactoslytransferase‐deficient (GalTKO) pig organs carry great potential as a solution to the shortage of human organ donors. These organs do not initiate hyperacute rejection but undergo acute humoral rejection mediated by xenoantibodies directed at non‐gal xenoantigens. The structure, specificity and germline origin of these antibodies has not been determined.METHODS: Three rhesus monkeys were immunized with sixty million GalTKO pig endothelial cells in order to induce high levels of xenoantibodies directed at GalTKO xenoantigens. The specificity of the immune response to GalTKO xenoantigens was confirmed by flow cytometry. Pre and post transplant peripheral blood B cells were used to prepare IgG and IgM cDNA libraries for identification of the IgVH genes encoding xenoantibodies.RESULTS: IgVH genes encoding anti‐non‐gal xenoantibodies were most closely related to the human germline progenitor V3‐21. The CDR3 region is unique and the J region is most similar to JH4 in 75.8% of the IgG sequences. The germline progenitors encoding anti‐non‐gal xenoantibodies are restricted and are 91% similar to the IGHV3‐11 alleles that encode anti‐carbohydrate xenoantibodies in primates transplanted with wild type and hDAF transgenic pig organs.CONCLUSIONS: The anti‐non‐gal xenoantibody response is restricted to usage of an IgVH repertoire known to encode antibodies to carbohydrates and glycolipids.