Comparative study of allograft survival of heterotopic and orthotopic small bowel transplantation in rat.

BACKGROUND

Small bowel allografts can either be placed heterotopically or orthotopically. In heterotopic small bowel transplantation (H-SBT), the host small intestine containing a substantial amount of gut-associated lymphoid tissue is removed, whereas in conventional orthotopic small bowel transplantation (O-SBT) it is retained. This study compared the allograft survival of H-SBT and O-SBT and evaluated the effect of retaining the host intestine in O-SBT in an altered O-SBT (AO-SBT) model.

METHODS

SBT was performed in a high-responder rat stain combination (blood group D Agouti --> Lewis). Immunosuppressive treatment consisting of a short course of FK506 (2 mg/kg/day IM for 3 days before transplantation and 0.3 mg/kg/day for 14 days after transplantation) was used.

RESULTS

Survival (mean +/- SD) of H-, O-, and AO-SBT untreated animals was 6.25+/-0.58 days, 6.5+/-0.58 days, and 6.7+/-0.25 days, respectively. With FK506 immunosuppression, survival of H-SBT animals was 49.3+/-13.17 days, whereas 75% (12/16) and 80% (4/5), respectively, of O-SBT and AO-SBT animals achieved indefinite survival (>120 days) with functioning grafts.

CONCLUSION

Our data suggest that heterotopic placement of intestinal allografts results in a more severe graft rejection than orthotopic placement. The indefinite survival of O-SBT is not due to of the removal of host intestine carrying a heavy load of gut-associated lymphoid tissue.