Blockade of transforming growth factor beta upregulates T-box transcription factor T-bet, and increases T helper cell type 1 cytokine and matrix metalloproteinase-3 production in the human gut mucosa

Background and Aims: The role of transforming growth factor beta (TGF beta) in inhibiting T cell function in the normal gut has been studied in animal models. However, the impact of TGF beta inhibition on T cells in the normal human gut remains poorly understood. The effect of TGFb blockade in normal intestinal biopsies grown ex vivo and lamina propria mononuclear cells (LPMCs) on T-bet, a T-box transcription factor required for T helper cell type (Th)1 differentiation, interferon gamma (IFN gamma) production, T cell apoptosis and matrix metalloproteinase (MMP)-3 production has therefore been tested. Methods: TGF beta transcripts were determined by quantitative reverse transcription-PCR in laser-captured gut epithelium and lamina propria. Biopsies and LPMCs were cultured with anti-TGF beta neutralising antibody. After 24 h culture, T-bet was determined by immunoblotting, and T cell apoptosis was assessed by flow cytometry. IFN gamma, tumour necrosis factor alpha (TNF alpha), interleukin (IL) 2, IL6, IL8, IL10, IL12p70 and IL17 were measured by ELISA. MMP-3 and tissue inhibitor of matrix metalloproteinase (TIMP)-1 were assessed by immunoblotting. Results: A higher number of TGF beta transcripts was found in the lamina propria than in the epithelium in normal gut. T-bet expression was significantly higher in biopsies and LPMCs cultured with anti-TGF beta antibody than in those cultured with control antibody. TGF beta blockade down-regulated T cell apoptosis, and induced a significant increase in IFN gamma, TNF alpha, IL2, IL6, IL8 and IL17 production. A higher expression of MMP-3, but not TIMP-1, was observed in the tissue and supernatant of biopsies treated with anti-TGF beta antibody. Conclusions: The findings support a crucial role for TGF beta in dampening T cell-mediated tissue-damaging responses in the human gut.