Cholera toxin subunit B inhibits IL-12 and IFN-{gamma} production and signaling in experimental colitis and Crohn's disease.

BACKGROUND AND AIMS: Cholera toxin B subunit (CT-B) is a powerful modulator of immune responses. The authors have previously demonstrated that oral administration of recombinant CT-B (rCT-B) is able to prevent and cure the Crohn's disease (CD)-like trinitrobenzene sulfonic acid (TNBS) mediated colitis. In this study they extended their observations and examined if rCT-B interferes with the molecular signaling underlying the Th1 type response both in TNBS colitis and in ex vivo human CD explants. METHODS: TNBS treated mice were fed with rCT-B, and IFN-gamma and IL-12 production by colonic lamina propria mononuclear cells (LPMC) was examined by ELISA. In vitro culture of mucosal explants from CD patients and non-inflammatory bowel disease controls, pre-incubated with rCT-B, were examined for IFN-gamma and IL-12 production by ELISA and semiquantitative reverse transcription polymerase chain reactions. STAT-1, -4, -6 activation and T-bet expression were examined following rCT-B treatment by western blotting both in TNBS treated mice and in human mucosal explants. RESULTS: rCT-B significantly reduced IL-12 and IFN-gamma secretion by LPMC from TNBS treated mice. Consistent with this, rCT-B inhibited both STAT-4 and STAT-1 activation and downregulated T-bet expression. Inhibition of Th1 signaling by CT-B associated with no change in IL-4 synthesis and expression of active STAT-6 indicating that rCT-B does not enhance Th2 cell responses. Moreover, in vitro treatment of CD mucosal explants with rCT-B resulted in reduced secretion of IL-12/IFN-gamma and inhibition of STAT-4/STAT-1 activation and T-bet expression. CONCLUSIONS: These studies indicate that CT-B inhibits mucosal Th1 cell signaling and suggest that rCT-B may be a promising candidate for CD therapy.

TGF-beta1 production in inflammatory bowel disease: differing production patterns in Crohn's disease and ulcerative colitis.

Transforming growth factor-beta (TGF-beta) is an inhibitory cytokine recognized as a key regulator of immunological homeostasis and inflammatory responses. TGF-beta is involved in experimental models of oral tolerance and in the pathogenesis of experimental colitis. Patients with inflammatory bowel disease (IBD) have inappropriate T cell responses to antigenic components of their own intestinal microflora, suggesting the presence of a disorder in the normal mucosal immune mechanism that ensures the down-regulation of responses to harmless constituents in the microflora. To evaluate the contribution of TGF-beta to this imbalance, we measured TGF-beta1 production by lamina propria mononuclear cells (LPMC) and T cells isolated from tissue specimens of patients with Crohn's disease (CD), ulcerative colitis (UC) and controls. Cells were cultured in the presence or absence of anti-CD2 plus anti-CD28 MoAbs and TGF-beta1 production in culture supernatants was measured by ELISA. LPMC isolated from CD patients produced significantly less TGF-beta1 than controls when stimulated via CD2 plus CD28 pathways (P = 0.001)] conversely, in UC patients increased production of TGF-beta1 compared to controls was observed (P = 0.0005). These differences were also observed with purified lamina propria (LP) T cells in both diseases and were associated with the presence of inflammation. Thus, TGF-beta1 production shows contrasting secretion in CD and in UC, probably as a consequence of the different Th polarization. The absolute or relative defect in TGF-beta1 production observed in CD and UC may contribute to the perpetuation of inflammation.