Transplantation of the entire small bowel in inbred rats using cyclosporine.

Inbred strains of rats were used to analyze unidirectional host-versus-graft disease (transplant rejection) without graft-versus-host disease in small intestinal transplants and the immunosuppressive properties of cyclosporine (CsA). Forty-six Lewis rats received heterotopic transplants of the entire small bowel in four groups: Lewis-to-Lewis isografts, without CsA; Lewis-to-Lewis isografts, with CsA (15 mg/kg/day); (Lewis X ACI)F1-to-Lewis allografts, without CsA; (Lewis X ACI)F1-to-Lewis allografts, with CsA. Small bowel rejection was associated with gross morphological changes that preceded all other findings. A histologic scoring system assessed the degree of transplant rejection. A characteristic transient weight loss was seen in animals rejecting their bowels. Glucose absorption was impaired and polyethylene glycol absorption increased during rejection. Cyclosporine inhibited all of these changes in allografted rats. It is concluded that daily administration of cyclosporine is effective in preventing the morphologic and functional changes of acute transplant rejection in intestinal allografts and does not change these parameters in transplants that are not rejecting.