title: Comparative study of allograft survival of heterotopic and orthotopic small bowel transplantation in rat.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Paediatric Surgery, Department of Surgery, University of Hong Kong Medical Centre, Queen Mary Hospital, Hong Kong SAR, P.R. China.
authors.forename: Wei Hong
authors.initials: WH
authors.lastname: Guo
authors.forename: Lina
authors.initials: L
authors.lastname: Tian
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Dallmann
authors.forename: Paul K H
authors.initials: PK
authors.lastname: Tam
mesh_terms: D000818:Animals; D006084:Graft Rejection / Q000276:immunology / Q000473:pathology*; D006085:Graft Survival / Q000276:immunology*; D007421:Intestine, Small / Q000276:immunology / Q000637:transplantation*; D008221:Lymphoid Tissue / Q000276:immunology* / Q000473:pathology; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew; D013514:Surgical Procedures, Operative / Q000379:methods; D014184:Transplantation, Homologous