Definition and characterization of chicken Gal alpha(1,3)Gal antibodies

Background The Gal alpha(1,3)Gal epitope is of interest as, in pig-to-prima te xenotransplantation, it is the ma jor target of naturally occurring huma n IgM and IgG antibodies, leading to hyperacute rejection. Human and Old Wo rld monkeys make anti-Gal alpha(1,3)Gal antibodies as they lack a functiona l gene and do not express Gala(1,3)Gal. Interestingly, the cultured fibrobl asts of some other species, such as chickens, have been reported also not t o express Gal alpha(1,3)Gal-if this is true for other tissues, and chickens do not express Gala(1,3)Gal antigen, then they would have anti-Gal antibod ies-which could have diagnostic and therapeutic value, particularly as chic ken antibodies do not fix mammalian complement. Methods. Standard serological methods were used to characterize the antibod ies. Several baboons received pig kidney xenografts that had been perfused with hyperimmune chicken anti-Gal antibodies. Results and Conclusions. We now demonstrate that chickens do not express Ga la(1,3)Gal on their red cells, leukocytes, or tissues, and that their serum contains large amounts of anti-Gal alpha(1,3)Gal antibodies. In addition, chickens could be immunized to produce high-titer, high-avidity antibodies (9.5x10(9) M-1)-an avidity considerably greater than that of the Gal alpha( 1,3)Gal binding lectin IB4 (2.9x10(8) M-1) or Gal antibodies in human serum (2.2x10(5) M-(1)). Chicken antibodies, obtained from both normal and immun ized chickens, could block the in vitro cytolysis of pig endothelial cells or lymphocytes by human or baboon antibodies. However, such antibodies test ed in vivo in pig-to-baboon xenotransplantation failed to block hyperacute rejection and, indeed, may have accelerated this.