Method for diagnosing rejection in small bowel transplantation.

Diagnosis of rejection in small bowel transplantation by the identification of a host-cell infiltrate is hampered by the physiological trafficking of host lymphocytes to the 'gut-associated lymphoid tissue' of the graft. This study compared physiological host-cell infiltration of small bowel grafts with that occurring in rejection and stable immunosuppression. Physiological host-cell infiltration, where the graft does not present an immune stimulus to the host, was assessed by transplanting bowel from DA to (DA x PVG) F1 hybrid rats. The extent of host-cell infiltration was determined by immunohistochemical analysis. In the lamina propria, considerable infiltration by host cells was seen, although it was significantly less than that in rejection or stable immunosuppression. By contrast, host cells were seen in the intraepithelial compartment only in rejection. Host-cell infiltration in the absence of an allogeneic stimulus suggests that histological identification of host cells in the lamina propria is not necessarily indicative of rejection. However, the presence of host cells in the intraepithelial compartment is specific for rejection in small bowel transplantation.