Pig-to-nonhuman primate islet xenotransplantation.
Transplantation of pancreatic islets from other species to man has the potential to cure diabetes, but whether such islet grafts will be subject to damage due to natural antibody-mediated hyperacute rejection is unknown. We have examined the fate of islet xenografts in a recipient with direct relevance to man, the cynomolgus monkey. Rabbit islets were prepared by an intraductal collagenase technique and incubated in neat rabbit, human, or cynomolgus serum, with and without heat inactivation, for up to 6 days. Islets were analyzed by flow cytometry for IGG and IGM binding, and scored for viability by supravital staining. For in vivo studies, isolated islets were prepared from 4 New Zealand White rabbits (15-34 x 10(3) islets 70-85% purity) and transplanted beneath the kidney capsule of normal cynomolgus monkeys after aggregation in either a rabbit or monkey blood clot. The tissue was retrieved at various times up to 4 days after transplantation and processed for light and electron microscopy. The results showed that rabbit islets bind heterophile antibody of both IGG and IGM subtypes. There was slow loss of islet viability in vitro over 3 days of culture in neat human or cynomolgus serum. Destruction of islets in vivo was more rapid with visible damage within 6 hr associated with neutrophil infiltration. Subsequently, there was heavy mononuclear cell infiltration leading to total destruction within 4 days. The results suggest that immediate mechanisms of graft rejection, possibly compliment and neutrophil mediated, represent a major barrier to islet xenotransplantation in humans.