EARLY HISTOPATHOLOGY OF SMALL-INTESTINAL DISCORDANT XENOGRAFTS

A descriptive study of a new model enabling serial biopsies of ongoing hyperacute rejection of small intestinal discordant xenografts is pre sented, In a series of guinea-pig-to-Lewis rat small bowel xenotranspl ants (n=7), aboral free ends of Thierry-Vella loops constructed from t he graft were sequentially biopsied at one-minute intervals up to ten minutes post-reperfusion and less frequently thereafter, In a guinea p ig-to-guinea pig (n=6) isograft series, biopsy controls for preservati on/ischemia-reperfusion injury were obtained, Xenoantibody sequestrati on in this model was evaluated in a separate series of transplants, ut ilizing an ELISA assay for rat anti-guinea pig natural antibodies. Pat hologic evaluation revealed a unique series of events characterized wi th microcirculatory failure and thrombosis progressing from the submuc osal vasculature to the lumen, Within the system's detection limits, c omplement deposition and P-selectin expression occurred as early as on e minute post-reperfusion, preceding the staining for IgM and IgG, Usi ng rat serum ELISAs, no significant difference in xenoantibody sequest ration was detected between the xenograft and isograft groups, The gui nea pig-to-rat discordant small bowel xenotransplantation is an effici ent small animal model to dissect the very early pathophysiologic even ts during hyperacute rejection.