Morphology of intestinal allograft rejection and the inadequacy of mucosal biopsy in its recognition.

Small intestinal segmental autografts and allografts in dogs were examined histologically to assess changes associated with the surgical technique, the effect of different luminal perfusates and for evidence of rejection. Some animals were immunosuppressed with Cyclosporin A. Specimens for examination were obtained by biopsy at regular intervals after transplantation, at death or when killed. Typical vascular changes of rejection were identified only within some allografts and in others the cause of graft failure remains conjectural. When there was rejection characteristic lesions were confined to the submucosa and muscle coats while changes in the mucosa were similar to those in the autografts. These mucosal features were affected by the nature of the perfusate and often appeared transiently after grafting. Mucosal biopsy as a way of monitoring intestinal allograft rejection neither reveals a sequential pattern of changes, nor provides a reliable method of recognition of the reaction. In contrast full thickness biopsies of the intestinal wall do appear to fulfil both of these requirements.