DEMONSTRATION OF IgM ANTIBODIES OF HIGH AFFINITY WITHIN THE ANTI-GAL??1-3GAL ANTIBODY REPERTOIRE

Publisher Website
Google Scholar
Abstract
Background. Human anti-Galα1-3Gal IgG and IgM xenoantibodies can distinguish between very similar epitopes with a high degree of selectivity. Methods. Anti-Galα1-3Gal antibodies were affinity isolated using two separate Galα1-3Gal-based immunoadsorbents, Galα1-3Gal itself and Galα1-3Galβ1-4Glc. IgG and IgM were separated using a protein G column. Antibody purity was achieved by serial adsorption/elutions from the columns. By this means, different antibody fractions were prepared that contained either IgG or IgM, reactive with either Galα1-3Gal, Galα1-3Galβ1-4Glc, or both. The dissociation equilibrium constants (Kd) of these antibodies were then measured using an IAsys biosensor. Results and Conclusions. Sera from two individuals were used and Kd values for one IgG (fraction 1A) and two IgM (fractions 1B and 2A) fractions were obtained. The Kd for the IgG was 4.85×10-7 M (fraction 1A). For IgM, the Kd values were higher at 7.8×10-10 M (fraction 1B) and 1.07×10-10 M (fraction 2A). Natural antipig antibodies include high affinity IgM that continue to be produced without class switch. The B cell mechanism behind this is not known. It may be possible to exploit this mechanism in future xenotransplantation strategies.