PHENOTYPIC AND FUNCTIONAL-CHARACTERISTICS OF INTESTINAL INTRAEPITHELIAL LYMPHOCYTES DURING ACUTE REJECTION OF SMALL-INTESTINAL ALLOGRAFTS

Infiltration of a transplanted organ by host lymphoid cells is the hal lmark of acute rejection. However, after intestinal transplantation, p hysiological lymphocyte migration may lead to host cell infiltration o f the graft even in the absence of rejection. It is unclear whether th is lymphocyte migration also involves the intraepithelial compartment of the graft or whether infiltration there is indicative of acute reje ction. We demonstrate here that host cell infiltration of the intestin al mucosa occurs both during acute rejection of a small bowel allograf t and, to a lesser extent, when rejection is prevented by immunosuppre ssion with FK506. The infiltrating host cells consisted of CD3(+) T ce lls with a predominant CD4(-)CD8(+) phenotype resembling intraepitheli al lymphocytes (IELs). Functional studies showed that the nonspecific cytolytic activity of IELs was not affected by acute rejection or by i mmunosuppression with FK506. These findings indicate that host cell in filtration of the intestinal mucosa does not connote an ongoing acute rejection. Furthermore, the decreased mucosal barrier function during acute rejection of intestinal allgrafts is probably not due to impaire d cytolytic activity of IELs.