Endotoxin in the peripheral blood during acute intestinal allograft rejection

Intestinal rejection is associated with increased gut permeability and bacterial translocation. The present study examined endotoxin and proinflammatory cytokines in the peripheral circulation during acute intestinal rejection. Heterotopic intestinal transplants were performed using Lewis rats (RT1¹) as donors and DA rats (RT1^a) as recipients. DA rats with intestinal isografts were used as controls. Serum samples were obtained at sacrifice on postoperative days (POD) 7 and 14. Lipopolysaccharide (LPS) was measured using the limulus amoebocyte lysate assay. Interleukin-1 (IL-1) and 6 (IL-6) and tumor necrosis factor- (TNF-) were measured using bioassays. Large amounts of LPS were detected in the serum of intestinal allograft recipients concurrent with the development of graft rejection. Serum IL-6 and TNF- levels were significantly elevated in the allograft recipients on both POD 7 and 14 when compared to DA isografts (P<0.05). Serum IL-1 activity was not detected in the allograft or isograft recipients at either of the two time points. Further studies are warranted to determine the role of intraluminal bacteria and their products in the pathophysiology of intestinal allograft rejection.