The impact of surgical technique on the development of graft versus host disease in a rat small intestinal transplant model.

The small intestine and its mesentery contain a large amount of lymphoid tissue that can mediate graft-versus-host disease (GVHD) in small intestinal transplant recipients. To assess the impact of surgical technique and the retention of the recipient's small intestine on GVHD intensity, 12 adult Lewis rats received heterotopic small bowel transplants and 12 received orthotopic small bowel transplants from Brown Norway donors. Twelve Lewis to Lewis heterotopic small-bowel-transplanted animals served as the control group. All recipients were given cyclosporine (10 mg/kg/alternate days) subcutaneously. The parameters followed were: weight gain and feed intake; clinical signs of GVHD; relative spleen weight; popliteal lymph node enlargement assay; and histological evaluation of spleen, liver, skin, native intestine, and transplanted intestine. According to the clinical scoring system, heterotopically transplanted animals were found to have a more severe GVHD than the orthotopic group. There were statistically significant differences between the relative spleen weights of the heterotopic transplant group and the control group (P = 0.001, 0.004, and 0.007 on days 7, 14, and 21, respectively) and between the heterotopic and orthotopic groups at 7 days (P = 0.037). Lymph node enlargement assays were statistically different between heterotopic and orthotopic groups (P = 0.019, 0.020, and 0.007 on days 7, 14, and 21, respectively). Histological evaluation of skin biopsy specimens also demonstrated that GVHD was indeed more severe in the heterotopic transplanted group when compared with orthotopically transplanted animals. These findings confirm that retention of the native small intestine in the heterotopic intestinal transplant model significantly increases the severity of GVHD following transplantation.