Nonlymphocyte-derived tumor necrosis factor is required for induction of colitis in recombination activating gene (RAG)2(-/-) mice upon transfer of CD4(+)CD45RB(hi) T cells

Chronic murine colitis is dependent on the CD154/CD40 pathway and can be attenuated by anti-CD154 administration

BACKGROUND & AIMS

Experimental colitis in most animal models is caused by dysregulation of T lymphocytes that display a T helper 1 (Th1) phenotype. CD154 (CD40L/gp39), a member of the tumor necrosis factor (TNF) family, is up-regulated on T cells on activation and has been shown to play a key role in the induction of a Th1 response. We investigated whether chronic experimental colitis is dependent on the CD154/CD40 pathway and whether disease can be prevented by anti-CD154 antibody treatment.

METHODS

Two models of chronic colitis were used: CD45Rb(hi) cell transfer into recombination activation gene-deficient (Rag(-/-)) mice and bone marrow transplant of tgepsilon26 animals. In both models, mice were reconstituted with cells from CD154-deficient animals. In another series of experiments, wild-type CD45Rb(hi) T cell-reconstituted recipients were treated with anti-CD154, either from the start of the experiment or after onset of disease.

RESULTS

T cells deficient in CD154 induced a milder clinical disease, less weight loss, and fewer histologic signs of colitis than wild-type cells. The level of interleukin 12 in the serum of CD154-deficient T-cell recipients was 5-fold less than that of wild-type cell recipients. Nevertheless, no signs of deviation from a Th1 phenotype were observed. Treatment with anti-CD154 antibodies substantially impaired disease development, even when started after the onset of colitis.

CONCLUSIONS

The CD154/CD40 pathway plays a critical role in Th1-induced chronic experimental colitis. Blocking CD154, even after the onset of disease, ameliorates colitis but does not induce a T helper 2 (Th2) phenotype.

Treatment of experimental (Trinitrobenzene sulfonic acid) colitis by intranasal administration of transforming growth factor (TGF)-beta1 plasmid: TGF-beta1-mediated suppression of T helper cell type 1 response occurs by interleukin (IL)-10 induction and IL-12 receptor beta2 chain downregulation

In this study, we show that a single intranasal dose of a plasmid encoding active transforming growth factor beta1 (pCMV-TGF-beta1) prevents the development of T helper cell type 1 (Th1)-mediated experimental colitis induced by the haptenating reagent, 2,4, 6-trinitrobenzene sulfonic acid (TNBS). In addition, such plasmid administration abrogates TNBS colitis after it has been established, whereas, in contrast, intraperitoneal administration of rTGF-beta1 protein does not have this effect. Intranasal pCMV-TGF-beta1 administration leads to the expression of TGF-beta1 mRNA in the intestinal lamina propria and spleen for 2 wk, as well as the appearance of TGF-beta1-producing T cells and macrophages in these tissues, and is not associated with the appearances of fibrosis. These cells cause marked suppression of interleukin (IL)-12 and interferon (IFN)-gamma production and enhancement of IL-10 production; in addition, they inhibit IL-12 receptor beta2 (IL-12Rbeta2) chain expression. Coadministration of anti-IL-10 at the time of pCMV-TGF-beta1 administration prevents the enhancement of IL-10 production and reverses the suppression of IL-12 but not IFN-gamma secretion. However, anti-IL-10 leads to increased tumor necrosis factor alpha production, especially in established colitis. Taken together, these studies show that TGF-beta1 inhibition of a Th1-mediated colitis is due to: (a) suppression of IL-12 secretion by IL-10 induction and (b) inhibition of IL-12 signaling via downregulation of IL-12Rbeta2 chain expression. In addition, TGF-beta1 may also have an inhibitory effect on IFN-gamma transcription.

Discovering the cause of inflammatory bowel disease: lessons from animal models

The precise cause of inflammatory bowel disease remains unclear. Relevant animal models are important tools for studying the underlying mechanisms of inflammation and disease pathogenesis. The purpose of this review is to summarize the various types of animal models available for use in inflammatory bowel disease research and to illustrate how these models have contributed to a better understanding of the etiopathogenesis of inflammatory bowel disease, particularly focusing on papers published during calendar year 1999. Studies using appropriate animal models have provided important discoveries in this field of investigation. These include determination of the key role that pathogenic and regulatory T cells, proinflammatory and immunoregulatory cytokines, indigenous bacterial flora, and putative predisposing genes play in the disease process. The availability of new animal models that closely resemble the human disease is expected to allow further characterization of the initiating event(s) in inflammatory bowel disease and lead to a possible cure for this devastating disease.