How to diagnose chronic rejection. A study in porcine intestinal allografts

Porcine small bowel allografts were followed for 18 weeks during immunosuppression with cyclosporine-A (CyA), azatioprine and prednisone. The mucosal alterations noted at the 12th week were epithelial vacuolation and loss of Goblet cells. Moderate infiltration of inflammatory cells, mainly lymphocytes, was found in the lamina propria. In addition, a few grafts exhibited oedema and fibrosis. Vessels already showed endothelial swelling and intimal proliferation at the 12th week. In the submucosa, the infiltration of inflammatory cells was not present till the 18th week. Further changes in the mucosa at the 18th week were the blunting of villi, cuboidal epithelium, crypt abscesses and epithelial atrophy. The histological alterations of mucosa and lamina propria existing in the full thickness biopsies were mostly also detectable in mucosal biopsies, provided that multiple biopsies were taken. Thus these parameters analyzed from mucosal biopsy material are suitable for the diagnosis and monitoring of chronic small bowel rejection. In autopsy, the most prominent features were in the mesenterial arteries: intimal proliferation, vasculitis, proliferation of media and endothelial alterations. The activity of the mucosal disaccharidases maltase and sucrase remained near the initial level till the 12th week and had decreased markedly by the 18th week.