POLYMORPHISM IN THE HUMAN ANTI-PIG NATURAL ANTIBODY REPERTOIRE - IMPLICATIONS FOR ANTIGEN-SPECIFIC IMMUNOADSORPTION

Background Anti-Gal alpha 1-3Gal antibodies cause hyperacute rejection (HAR) in pig-to-primate xenotransplantation. Long-term graft survival has not been achieved despite abrogation of HAR using transgenic pigs . IgG and IgM anti-Gal alpha 1-3Gal also play a role in the events fol lowing abrogation of HAR. Characterizing these antibodies and developi ng a system for their removal is therefore crucial to future success i n xenotransplantation. Methods and Results. We have developed a neogly coprotein enzyme-linked immunosorbent assay to probe the precise antig enic requirements for the binding of anti-Gal alpha 1-3Gal and have an alyzed 77 normal sera. Sixty-six percent of individuals have IgG that recognizes the Gal alpha 1-3Gal di-, tri-, and pentasaccharides (D, T, and P, respectively), termed DTP phenotype, The frequency of other ph enotypes was - -P, 13%; -TP, 12%; D-P, 8%; and DT-, 1%. The IgG subcla sses found were IgG, (95%), IgG, (34%), IgG, (31%), and IgG, (17%). Ig M in 91% of individuals recognized all three antigens. Further antibod y heterogeneity was demonstrated when immunoadsorbents derived from Ga l alpha 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc (PENTA) were tes ted. Gal alpha 1-3Gal beta 1-4Glc (TRI 6) or PENTA agarose were effect ive for IgG removal in all individuals. For IgM removal, two deoxy der ivatives were completely successful in 73% of individuals. Combining t he Gal alpha 1-3Gal (DI) and TRI 6 agarose produced an adsorbent that completely removed anti-Gal alpha 1-3Gal IgG and IgM in all individual s tested. Conclusions. Although the polymorphism in the anti-Gal alpha 1-3Gal repertoire, which we have demonstrated, represents a major obs tacle to the development of an effective immunoadsorbent, the combinat ion of DI and TRI 6 agarose appears sufficient for pig-to-human xenotr ansplantation.