PROTECTION OF PIG-KIDNEY (PK15) CELLS FROM THE CYTOTOXIC EFFECT OF ANTI-PIG ANTIBODIES BY ALPHA-GALACTOSYL OLIGOSACCHARIDES

Anti-pig antibodies in human and baboon serum are believed to be direc ted against alpha-galactosyl (alphaGal) epitopes expressed on various pig cells, including vascular endothelia. We have investigated the eff ect of human sera on the PK15 pig kidney cell line, which abundantly e xpresses alphaGal epitopes. To quantitate cell viability, we have used a staining method that differentiates live cells from dead ones. Vari ous carbohydrates (n=28) were added individually to serum at concentra tions of 0.125-50 mg/ml. Unmodified serum caused approximate 100% PK15 cell death within 60 min. Carbohydrates that were not alphaGal based did not significantly protect PK15 cells. Of the alphaGal-based carboh ydrates, only B disaccharide protected PK15 cells from both human and baboon serum (76% and 93% protection, respectively, at 1 mg/ml). Three alphaGal oligosaccharides provided approximately 80-90% protection ag ainst both human and baboon sera at a concentration of 10 mg/ml. Three other closely related structures protected only against baboon serum (> 80%) at high concentration (50 mg/ml), suggesting a difference in a nti-pig antibody affinity between baboon and man. Specific anti-alphaG al antibody-depleted serum caused < 10% pig cell death, whereas the an tibodies eluted from the alphaGal columns caused > 70% pig cell death. In conclusion, this study provides further evidence that (1) alphaGal structures are the targets for human and baboon anti-pig antibodies, and (2) there may be a therapeutic role for the infusion of specific a lphaGal carbohydrates, or for antibody removal using alphaGal immunoaf finity columns, in order to prevent hyperacute rejection of pig organs in man.