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

Abstract

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.

Fig. 1

TGF-β1 production by isolated LPMC from: (a) small bowel controls, small bowel CD involved tissue (b) colon controls, colon CD involved tissue and UC involved tissue. TGF-β1 production was measured in unstimulated cultures (open symbols) and in αCD2 + αCD28 stimulated cultures (closed symbols). Median is indicated by horizontal bars. (a) *P = 0·001 small bowel CD involved tissue versus small bowel controls] (b) *P = 0·008 colon CD involved tissue versus colon controls, **P = 0·0005 UC involved tissue versus colon controls.

Fig. 2

TGF-β1 production by LP purified T lymphocytes. (a) Small bowel controls, CD involved tissue] (b) colon controls, UC involved tissue. Bars represent median. TGF-β1 production was measured in unstimulated cultures (open symbols) and in αCD2⁺ αCD28 stimulated cultures (closed symbols). (a) *P = 0·009 small bowel CD versus small bowel controls (b) *P = 0·009 UC versus colon control. LPMC TGF-β1 production in parallel cultures stimulated with αCD2⁺ αCD28 MoAbs were: small bowel controls: range: 48–124 pg/ml, median: 62·5, small bowel CD: range: 2·18–175 pg/ml, median: 16·8. colon controls: range: 23·1–73 median 47·5 pg/ml, UC: range 90–249 pg/ml median 160.

Fig. 3

TGF-β1 production by isolated LPMC from: (a) small bowel controls, small bowel CD involved tissue, small bowel CD uninvolved tissue] (b) colon controls, UC involved tissue, UC uninvolved tissue. Bars represent median. TGF-β1 production was measured in unstimulated cultures (open symbols) and in αCD2 + αCD28 stimulated cultures (closed symbols).