ACUTE REJECTION OF PORCINE SMALL-BOWEL ALLOGRAFT - AN EXTENDED HISTOLOGICAL SCORING SYSTEM

Using nonimmunosuppressed piglet small bowel grafts, we performed a de tailed histological study on acute rejection and analyzed altogether 4 5 different histological parameters throughout the bowel wall, in 10 a llografts and 6 autografts. Heterotopic grafts were followed by full-t hickness biopsies every other day beginning on the 3rd day after trans plantation. The parameters were scored from 0 to 3 according to the se verity of the change and the values of every variable were compared st atistically between the 2 groups. The earliest significant changes, be ginning on days 3-5, were infiltration of inflammatory cells and pyron inophilia among these cells in lamina propria; edema, fibrosis, and in flammation in submucosa and muscularis; vacuolar degeneration of myocy tes; and endothelial and intimal changes in vessels. Villous blunting and cuboidal epithelium were the other early markers. On day 7, the ep ithelial and vascular changes became most significant. We want to emph asize especially the vascular parameters: endothelial swelling and pro liferation, intimal thickening, intramural inflammation, and obliterat ion of the lumen. The dilatation of lymph vessels and changes of Peyer 's patches had no value in the estimation of rejection. All allografts became necrotic by day 11 after transplantation.