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.

Immunologic basis of transplant-associated arteriosclerosis.

Although immunosuppressive therapy minimizes the risk of graft failure due to acute rejection, transplant-associated arteriosclerosis of the coronary arteries remains a significant obstacle to the long-term survival of heart transplant recipients. The participation of specific inflammatory cell types in the genesis of this lesion was examined in a mouse model in which carotid arteries were transplanted across multiple histocompatibility barriers into seven mutant strains with immunologic defects. An acquired immune response--with the participation of CD4+ (helper) T cells, humoral antibody, and macrophages--was essential to the development of the concentric neointimal proliferation and luminal narrowing characteristic of transplant arteriosclerosis. CD8+ (cytotoxic) T cells and natural killer cells were not involved in the process. Arteries allografted into mice deficient in both T-cell receptors and humoral antibody showed almost no neointimal proliferation, whereas those grafted into mice deficient only in helper T cells, humoral antibody, or macrophages developed small neointimas. These small neointimas and the large neointimas of arteries grafted into control animals contained a similar number of inflammatory cells; however, smooth muscle cell number and collagen deposition were diminished in the small neointimas. Also, the degree of inflammatory reaction in the adventitia did not correlate with the size of the neointima. Thus, the reduction in neointimal size in arteries allografted into mice deficient in helper T cells, humoral antibody, or macrophages may be accounted for by a decrease in smooth muscle cell migration or proliferation.

Potentiation of epidermal growth factor receptor-mediated oncogenesis by c-Src: implications for the etiology of multiple human cancers.

c-Src is a nontransforming tyrosine kinase that participates in signaling events mediated by a variety of polypeptide growth factor receptors, including the epidermal growth factor receptor (EGFR). Overexpression and continual ligand stimulation of the EGFR results in morphological transformation of cells in vitro and tumor development in vivo. Elevated levels of c-Src and the EGFR are found in a variety of human malignancies, raising the question of whether c-Src can functionally cooperate with the EGFR during tumorigenesis. To address this issue, we generated c-Src/EGFR double overexpressors and compared their proliferative and biochemical characteristics to those of single overexpressors and control cells. We found that in cells expressing high levels of receptor, c-Src potentiated DNA synthesis, growth in soft agar, and tumor formation in nude mice. Growth potentiation was associated with the formation of a heterocomplex between c-Src and activated EGFR, the appearance of a distinct tyrosyl phosphorylation on the receptor, and an enhancement of receptor substrate phosphorylation. These findings indicate that c-Src is capable of potentiating receptor-mediated tumorigenesis and suggest that synergism between c-Src and the EGFR may contribute to a more aggressive phenotype in multiple human tumors.