The comparative importance of E. coli antigen in granulomatous colitis of Boxer dogs

Granulomatous colitis of Boxer dogs is characterized by mucosal and submucosal infiltration by abundant large macrophages and lymphocytes and plasma cells. Involved intestine is thickened, corrugated and ulcerated. The macrophages that occur in colon, cecum and regional lymph nodes are PAS-positive, lipid-rich, contain cholesterol, and some of the time can be seen to hold bacteria. Paraffin tissue blocks of formalin-fixed colon and colic lymph nodes from 10 cases were cut at 5 microm and immunostained by a streptavidin-biotin immunoperoxidase technique, employing primary antibodies against Escherichia coli, E. coli 0157: 2, Campylobacter, C. jejuni-coli, Yersinia pseudotuberculosis, Salmonella, Shigella, Pseudomonas and Lawsonia intracellularis. The macrophages in the lamina propria and submucosa, as well as those in aggregates in regional lymph nodes, showed immunoreactivity with polyclonal E. coli antibody in all 10 cases. Tissues lacking granulomas were negative, as were those reacted with the other eight antibodies, with the exception that there was rare focal staining for Campylobacter, Lawsonia and Salmonella in a few dogs. We believe these results identify the causative agent of this granulomatous disease of Boxer dogs, a disease with great histologic and etiologic similarity to granulomatous leptomeningitis of Beagle dogs, and malacoplakia and xanthogranulomatous cholecystitis of man. Macrophages that are immunopositive for E. coli antigen occur in Crohn's disease as well, where their significance is less well understood.