On the etiology of Crohn disease.

Crohn disease (CD) is a chronic, panenteric intestinal inflammatory disease. Its etiology is unknown. Analogous to the tuberculoid and lepromatous forms of leprosy, CD may have two clinical manifestations. One is aggressive and fistulizing (perforating), and the other is contained, indolent, and obstructive (nonperforating) [Gi]-berts, E. C. A. M., Greenstein, A. J., Katsel, P., Harpaz, N. & Greenstein, R. J. (1994) Proc. Natl. Acad. Sci. USA 91, 12721-127241. The etiology, if infections, may be due to Mycobacterium paratuberculosis. We employed reverse transcription PCR using M. paratuberculosis subspecies-specific primers (IS 900) on total RNA from 12 ileal mucosal specimens (CD, n = 8; controls, n = 4, 2 with ulcerative colitis and 2 with colonic cancer). As a negative control, we used Myobacterium avium DNA, originally cultured from the drinking water of a major city in the United States. cDNA sequence analysis shows that all eight cases of Crohn's disease and both samples from the patients with ulcerative colitis contained M. paratuberculosis RNA. Additionally, the M. avium control has the DNA sequence of M. paratuberculosis. We demonstrate the DNA sequence of M. paratuberculosis from mucosal specimens from humans with CD. The potable water supply may be a reservoir of infection. Although M. paratuberculosis signal in CD has been previously reported, a cause and effect relationship has not been established. In part, this is due to conflicting data from studies with empirical antimycobacterial therapy. We conclude that clinical trials with anti-M. paratuberculosis therapy are indicated in patients with CD who have been stratified into the aggressive (perforating) and contained (nonperforating) forms.

Observations on the Kveim reaction using an animal model of granulomatous bowel disease.

Striking differences were observed between the visceral and cutaneous responses after tests with validated Kveim and normal spleen suspensions in a guinea pig model of granulomatous bowel disease. Five of six animals sensitised with BCG showed positive responses at the ileal Kveim test site whereas all six had negative cutaneous Kveim tests. Conversely, two of six animals sensitised with irradiated Mycobacterium leprae showed positive cutaneous Kveim tests and only one a positive response in the ascending colon. All six showed negative responses at the ileal Kveim test site. No positive visceral or cutaneous responses were observed in either group of animals after tests with normal spleen suspension. These findings are discussed in relation to the positive Kveim responses previously reported among patients with Crohn's disease, tuberculoid and lepromatous leprosy, and among seemingly healthy BCG vaccinated subjects. The findings provide further evidence in support of a possible mycobacterial aetiology for sarcoidosis and Crohn's disease.

Human gut wall reactivity to monoclonal antibodies against M. avium glycolipid in relation to Crohn's disease (preliminary results).

In order to evaluate the role of mycobacteria in the pathogenesis of Crohn's disease (CD), 4 monoclonal antibodies (McAb's) raised against M. avium specific glycolipid were tested on bowel resection specimens of CD patients and relevant controls. Two of the McAb's had shown a positive reaction to a CD-Mycobacteria isolate (CD-Myc). The same two McAb's showed a positive reaction within the gut wall, not only in CD patients, but also in the controls. In non-CD controls, however, the positive cells were limited to the lamina propria, while in CD patients positivity was also found in the submucosa and subserosa. Furthermore the mean number of positive cells in CD patients tends to be higher than in the control groups. Using double staining techniques the positive cells appeared to be B-cells of IgA isotype. These preliminary results indicate that mycobacteria might play a role in the pathogenesis of Crohn's disease.