Donor cell infiltration of recipient tissue as an indicator of small bowel allograft rejection in the rat

This study assessed whether screening of host tissues for graft cells could be used as an effective monitor of rejection following small bowel transplantation. Allogeneic rat small bowel transplantation was performed with or without cyclosporin (CyA) immunosuppression and cellular infiltration of host tissues assessed by immunohistological staining. Without immunosuppression, grafts were completely rejected within 1 week. CyA treatment for 7 days preserved the graft for 28 days although there was histological evidence of mild rejection in some of the animals studied. Continuous CyA treatment preserved the graft for up to 56 days. The peripheral lymph nodes and spleens of untreated animals were transiently infiltrated by low numbers of donor cells that disappeared by day 6. There was a marked donor cell infiltration of the lymph nodes and spleens of 7-day, CyA-treated animals that was maintained during the administration of immunosuppressive therapy but that declined thereafter. Continuous CyA treatment sustained donor cell infiltration up to day 56. These findings suggest the presence of donor cells in recipient lymph nodes and spleen to be indicative of effective control of rejection and their disappearance to be predictive of developing rejection responses. Examination of recipient peripheral tissues for donor cells may provide an improved technique for monitoring clinical small bowel transplantation.