IL-2 is positively involved in the development of colitogenic CD4+ IL-7R alpha high memory T cells in chronic colitis.

IL-2 and IL-7 share a common gamma-chain receptor and are critical for T-cell homeostasis. We aimed to clarify the reciprocal roles of IL-2 and IL-7 in the development and persistence of chronic colitis. We performed a series of adoptive transfers of IL-2(-/-) CD4(+)CD45RB(high) T cells into RAG-2(-/-) mice and assessed the role of IL-2 in the induction of IL-7R alpha on colitogenic CD4(+) T cells and the development of chronic colitis. RAG-2(-/-) mice transferred with WT but not with IL-2(-/-) CD4(+)CD45RB(high) T cells developed Th1/Th17-mediated colitis. Consistently, re-expression of IL-7R alpha was severely impaired on IL-2(-/-) but not on WT CD4(+) T cells from the transferred mice. To exclude a contribution of the preclinical autoimmunity of IL-2(-/-)mice, WT Ly5.1(+) or IL-2(-/-) Ly5.2(+) CD4(+)CD45RB(high) T cells from GFP mice previously transplanted with the same number of WT and IL-2(-/-) BM cells were transferred into RAG-2(-/-) mice. RAG-2(-/-) mice transferred with IL-2(-/-)-derived CD4(+)CD45RB(high) T cells did not develop colitis, but their splenic CD4(+) T cells changed from effector-memory to central-memory type. These results show that IL-2 is critically involved in the establishment and maintenance of IL-7-dependent colitogenic memory CD4(+)IL-7R alpha(high) T cells.

Prevalence of metabolic syndrome is comparable between inflammatory bowel disease patients and the general population.

BACKGROUND: Metabolic syndrome (MS) is associated with an increased risk of cardiovascular disease. However, its prevalence in inflammatory bowel disease (IBD) patients remains largely unknown. This study was planned to determine the prevalence of MS in Japanese IBD patients. METHODS: The prevalence of MS among outpatients with IBD aged 18 or older was studied using the modified National Cholesterol Education Program Adult Treatment Panel III definition. RESULTS: A total of 107 quiescent IBD patients, including 76 ulcerative colitis (UC) patients and 31 Crohn's disease (CD) patients, were studied. Sufficient data were collected from a total of 102 patients. Prevalence of MS was significantly higher in UC (23.0%) patients compared to CD patients (7.1%). MS prevalence was substantially higher among male IBD patients (21.1%) compared to female IBD patients (12.9%), particularly in patients over 30 years of age. No difference was observed in the prevalence of MS between our IBD cohort and the general population in both males and females aged 40 years and older (P = 0.707 in males, P = 0.328 in females). IBD patients with MS were also older than those without (50.2 ± 15.0 vs. 38.0 ± 11.9 years, P = 0.013). In a logistic regression analysis, age was the statistically significant predictor of MS among IBD patients. The odds ratio (95% confidence interval) was 1.064 (1.017-1.114). CONCLUSIONS: Prevalence of metabolic syndrome in our IBD patients was comparable to that of the general population. Because age was the independent risk factor for developing MS, evaluation for MS is needed for elderly IBD patients.

IL-7 is essential for lymphopenia-driven turnover of colitogenic CD4(+) memory T cells in chronic colitis.

We previously demonstrated that IL-7 is essential for the persistence of T-cell-mediated colitis, by showing that adoptive transfer of CD4(+)CD45RB(high) T cells into IL-7(-/-) x RAG-1(-/-) mice did not induce colitis; and that intestinal IL-7 is not essential for this colitis model, by showing that IL-7(-/-) x RAG-1(-/-) mice parabiosed with colitic CD4(+)CD45RB(high) T-cell-transferred RAG-1(-/-) mice developed colitis. Here, we investigated the role of IL-7 in the maintenance of colitogenic CD4(+) T cells by surgically separating these parabionts. Surprisingly, the separated IL-7(-/-) x RAG-1(-/-) mice were consistently diseased after separation, although no IL-7 mRNA was detected in the tissues of separated IL-7(-/-) x RAG-1(-/-) partners. CD4(+) T cells isolated from the separated RAG-1(-/-) or IL-7(-/-) x RAG-1(-/-) mice were then transferred into new RAG-1(-/-) or IL-7(-/-) x RAG-1(-/-) mice. Regardless of the source of donor cells, RAG-1(-/-) recipients developed colitis, whereas IL-7(-/-) x RAG-1(-/-) recipients did not. Collectively, these results demonstrate that IL-7 is essential for lymphopenia-driven turnover of colitogenic CD4(+) T cells rather than the maintenance of those cells in established colitic mice. They also provide a basis for the timing of IL-7/IL-7R blockade for the treatment of inflammatory bowel diseases.

RANK-RANKL signaling pathway is critically involved in the function of CD4+CD25+ regulatory T cells in chronic colitis.

It is now clear that functional CD4(+)CD25(+) regulatory T (T(R)) cells exist as part of the normal immune population and prevent the development of intestinal inflammation. We have recently shown that CD4(+)CD25(+) T(R) cells reside in the intestine and control intestinal homeostasis in humans and mice. In this study, we demonstrate that the TNF family molecule RANKL and its receptor RANK are critically involved in controlling the function of CD4(+)CD25(+) T(R) cells in the intestine. We first found that RANKL was preferentially expressed on both CD4(+)CD25(+) T(R) cells and colitogenic CD4(+) T cells, whereas RANK was expressed on dendritic cells. Although neutralizing anti-RANKL mAb did not affect T(R) activity of CD4(+)CD25(+) T(R) cells to suppress the proliferation of CD4(+) responder cells in vitro, in vivo administration of anti-RANKL mAb abrogated CD4(+)CD25(+) T(R) cell-mediated suppression of colitis induced by adoptive transfer of CD4(+)CD45RB(high) T cells into SCID mice. Interestingly, an adoptive transfer experiment using Ly5.1(+)CD4(+)CD45RB(high) cells and Ly5.2(+)CD4(+)CD25(+) T(R) cells revealed that the ratio of CD4(+)CD25(+) T(R) cells in total CD4(+) T cells in inflamed mucosa was significantly decreased by anti-RANKL mAb treatment. Consistent with this, the expression of RANK on lamina propria CD11c(+) cells from colitic mice was significantly increased as compared with that from normal mice, and in vitro treatment with anti-RANKL mAb suppressed the expansion of CD4(+)Foxp3(+) T(R) cells in culture with colitic lamina propria CD11c(+) cells. Together, these results suggest that the RANK-RANKL signaling pathway is critically involved in regulating the function of CD4(+)CD25(+) T(R) cells in colitis.

Signaling pathway via TNF-alpha/NF-kappaB in intestinal epithelial cells may be directly involved in colitis-associated carcinogenesis.

Treatment with anti-TNF-alpha MAb has been accepted as a successful maintenance therapy for patients with inflammatory bowel diseases (IBD). Moreover, it has been recently reported that blockade of TNF receptor (TNFR) 1 signaling in infiltrating hematopoietic cells may prevent the development of colitis-associated cancer (CAC). However, it remains unclear whether the TNF-alpha signaling in epithelial cells is involved in the development of CAC. To investigate this, we studied the effects of anti-TNF-alpha MAb in an animal model of CAC by administration of azoxymethane (AOM) followed by sequential dextran sodium sulfate (DSS) ingestion. We observed that the NF-kappaB pathway is activated in colonic epithelia from DSS-administered mice in association with upregulation of TNFR2 rather than TNFR1. Immunoblot analysis also revealed that the TNFR2 upregulation accompanied by the NF-kappaB activation is further complicated in CAC tissues induced in AOM/DSS-administered mice compared with the nontumor area. Such NF-kappaB activity in the epithelial cells is significantly suppressed by the treatment of MP6-XT22, an anti-TNF-alpha MAb. Despite inability to reduce the severity of colitis, sequential administration of MP6-XT22 reduced the numbers and size of tumors in association with the NF-kappaB inactivation. Taken together, present studies suggest that the TNFR2 signaling in intestinal epithelial cells may be directly involved in the development of CAC with persistent colitis and imply that the maintenance therapy with anti-TNF-alpha MAb may prevent the development of CAC in patients with long-standing IBD.

Persistent retention of colitogenic CD4+ memory T cells causes inflammatory bowel diseases to become intractable.

Despite the advent of an age when "malignant" leukemia is cured by bone marrow transplantation, "benign" inflammatory bowel diseases (IBDs) are still intractable lifelong diseases. Why is it that once an IBD develops it lasts a long time? We propose that, the same as in the response to vaccination, immune memory T cells that remember the disease are formed in IBDs and, perceiving them as "benign T-cell leukemia"-like lifelong pathology that hematogenously spreads throughout the body, we here propose that the bone marrow itself, which produces large amounts of the survival factor IL-7, is the reservoir for colitogenic CD4(+) memory T cells responsible for the intractability of IBDs.

FTY720 suppresses the development of colitis in lymphoid-null mice by modulating the trafficking of colitogenic CD4+ T cells in bone marrow.

2-amino-2-(2-[4-octylphenyl]ethyl)-1,3-propanediol hydrochloride (FTY720) suppresses T-cell egress from LN, thereby preventing pathogenic T cells from migrating toward disease sites. However, little is known about whether FTY720 could control the trafficking of T cells without the presence of lymphoid tissues. Here we demonstrate that FTY720 treatment suppresses the recirculation of CD4(+) T cells in splenectomized (SPX) lymphotoxin-alpha(-/-) (LT-alpha(-/-)) mice that lack LN and spleen, as shown by peripheral blood (PB) lymphopenia in FTY720-treated SPX LT-alpha(-/-) mice. In a short-term transfer experiment, the cell number of transferred Ly5.1(+)CD4(+) T cells recovered from host FTY720-treated SPX LT-alpha(-/-) mice (Ly5.2(+)) was markedly decreased in PB, but conversely increased in BM. Notably, FTY720 treatment prevented the development of colitis that is otherwise induced in untreated SPX LT-alpha(-/-) x RAG-2(-/-) mice upon transfer of colitic lamina propria CD4(+) T cells. In such mice, the number of CD4(+) T cells in PB or lamina propria of FTY720-treated SPX LT-alpha(-/-) x RAG-2(-/-) recipients was significantly reduced, but that in the BM was significantly increased as compared with untreated control mice. Altogether, the present results indicate that FTY720 treatment may offer an additional role to direct trafficking of CD4(+) T cells in BM, resulting in the prevention of colitis.

Colitogenic CD4+ effector-memory T cells actively recirculate in chronic colitic mice.

BACKGROUND: Although the clinical usefulness of leukocytapheresis for patients with inflammatory bowel disease (IBD) has been reported as a selective removal therapy targeting pathogenic immune cells in blood circulation, it remains unclear whether colitogenic CD4(+) T cells continuously recirculate in peripheral blood during the chronic phase of colitis. METHODS: To resolve this question we conducted a series of in vivo experiments using a murine chronic colitis model induced by adoptive transfer of CD4(+)CD45RB(high) cells into SCID mice in combination with a parabiosis system. RESULTS: In colitic SCID recipients, first, almost all CD4(+) CD45RB(high) donor cells were converted to CD4(+)CD44(high)CD62L(-) IL-7Ralpha(high) effector-memory T (T(EM)) cells at 8 weeks after transfer and were distributed throughout the whole body, including colonic lamina propria, mesenteric lymph nodes, thoracic duct, peripheral blood, spleen, and bone marrow. Second, SCID mice retransferred with the colitic peripheral blood CD4(+) T cells developed colitis that is identical to the original colitis. Third, CD4(+) cells in parabionts between established colitic RAG-2(-/-) mice induced by adoptive transfer of Ly5.1(+) or Ly5.2(+) CD4(+)CD45RB(high) T cells were well mixed in almost equal proportions at various sites 2 weeks after parabiosis surgery, and the redistribution of Ly5.1(+) and Ly5.2(+) CD4(+) T cells was significantly suppressed in FTY720-treated parabionts. CONCLUSIONS: Together, these findings indicate that colitogenic CD4(+) T(EM) cells continuously recirculate in established colitic mice, suggesting that therapeutic approaches targeting systemic CD4(+) T(EM) cells, such as bone marrow transplantation, rather than those targeting only intestinal CD4(+) T cells, may be feasible for the treatment of IBD.

Intestinal lamina propria retaining CD4+CD25+ regulatory T cells is a suppressive site of intestinal inflammation.

It is well known that immune responses in the intestine remain in a state of controlled inflammation, suggesting that not only does active suppression by regulatory T (T(REG)) cells play an important role in the normal intestinal homeostasis, but also that its dysregulation of immune response leads to the development of inflammatory bowel disease. In this study, we demonstrate that murine CD4(+)CD25(+) T cells residing in the intestinal lamina propria (LP) constitutively express CTLA-4, glucocorticoid-induced TNFR, and Foxp3 and suppress proliferation of responder CD4(+) T cells in vitro. Furthermore, cotransfer of intestinal LP CD4(+)CD25(+) T cells prevents the development of chronic colitis induced by adoptive transfer of CD4(+)CD45RB(high) T cells into SCID mice. When lymphotoxin (LT)alpha-deficient intercrossed Rag2 double knockout mice (LTalpha(-/-) x Rag2(-/-)), which lack mesenteric lymph nodes and Peyer's patches, are transferred with CD4(+)CD45RB(high) T cells, they develop severe wasting disease and chronic colitis despite the delayed kinetics as compared with the control LTalpha(+/+) x Rag2(-/-) mice transferred with CD4(+)CD45RB(high) T cells. Of note, when a mixture of splenic CD4(+)CD25(+) T(REG) cells and CD4(+)CD45RB(high) T cells are transferred into LTalpha(-/-) x Rag2(-/-) recipients, CD4(+)CD25(+) T(REG) cells migrate into the colon and prevent the development of colitis in LTalpha(-/-) x Rag2(-/-) recipients as well as in the control LTalpha(+/+) x Rag2(-/-) recipients. These results suggest that the intestinal LP harboring CD4(+)CD25(+) T(REG) cells contributes to the intestinal immune suppression.

Extracorporeal elimination of TNF-alpha-producing CD14(dull)CD16(+) monocytes in leukocytapheresis therapy for ulcerative colitis.

BACKGROUND: In recent years leukocytapheresis using a leukocyte removal filter (known as lymphocytapheresis, LCAP) has been applied to the treatment of various autoimmune diseases including ulcerative colitis (UC). In the present study we aimed to clarify how LCAP therapy modifies inflammatory responses by modulating circulating TNF-alpha-producing monocytes. METHODS: Mononuclear cells were obtained from blood before and after the first treatment, and the expression profiles of various immune cells (naive versus. memory, regulatory CD4(+)CD25(bright) versus non-regulatory CD4(+)CD25(-) T cells, and CD14(+)CD16(-) versus CD14(dull)CD16(+) monocytes) were assessed. To evaluate immunological differences between CD14(+)CD16(-) and CD14(dull)CD16(+) monocytes, the expression of TNF-alpha, IL-6, IL-12, IL-10, IL-18, surface toll-like receptor 2 (TLR2), TLR4, and other activation markers including HLA-DR, CD80 and CD86, as well as cytokine profiles, were analyzed. RESULTS: LCAP treatment selectively removed CD14(dull)CD16(+) monocytes, which preferentially produce TNF-alpha and IL-12 and express HLA-DR, CD80, CD86, and TLR2, compared with the major fraction of CD14(+)CD16(-) monocytes, which conversely produce a higher amount of IL-10. In addition, the CD4(+)CD45RO(+)CD62L(-)/CD4(+)CD45RO(+)CD62L(+) ratio was significantly lower after LCAP therapy. However, the CD4(+)CD25(bright)/total CD4(+) ratio did not change. CONCLUSIONS: The present findings revealed the real target of proinflammatory CD14(dull)CD16(+) monocytes removed during LCAP treatment of UC and that LCAP might be used as an extracorporeal anti-TNF-alpha therapy, expanding the clinical applications of this procedure to include the treatment of Crohn's disease.

Bone marrow retaining colitogenic CD4+ T cells may be a pathogenic reservoir for chronic colitis.

BACKGROUND & AIMS: Although bone marrow (BM) is known as a primary lymphoid organ, it also is known to harbor memory T cells, suggesting that this compartment is a preferential site for migration and/or selective retention of memory T cells. We here report the existence and the potential ability to induce colitis of the colitogenic BM CD4+ memory T cells in murine colitis models. METHODS: We isolated BM CD4+ T cells obtained from colitic severe combined immunodeficient mice induced by the adoptive transfer of CD4+ CD45RB(high) T cells and colitic interleukin (IL)-10(-/-) mice that develop colitis spontaneously, and analyzed the surface phenotype, cytokine production, and potential activity to induce colitis. Furthermore, we assessed the role of IL-7 to maintain the colitogenic BM CD4+ T cells. RESULTS: A high number of CD4+ T cells reside in the BM of colitic severe combined immunodeficient mice and diseased IL-10(-/-) mice, and they retain significant potential to induce type-1 T helper-mediated colitis in an IL-7-dependent manner. These resident BM CD4+ T cells have an effector memory (T(EM); CD44(high)CD62L(-)IL-7R(high)) phenotype and preferentially are attached to IL-7-producing BM cells. Furthermore, the accumulation of BM CD4+ T(EM) cells was decreased significantly in IL-7-deficient recipients reconstituted with the colitogenic lamina propria CD4+ T(EM) cells. CONCLUSIONS: Collectively, these findings suggest that BM-retaining colitogenic CD4+ memory T cells in colitic mice play a critical role as a reservoir for persisting lifelong colitis.

Ameliorating effect of saporin-conjugated anti-CD11b monoclonal antibody in a murine T-cell-mediated chronic colitis.

BACKGROUND: Crohn's disease (CD) is an inflammatory bowel disease that is associated with several changes in the immune system, including an increased number of infiltrating macrophages. These macrophages release a variety of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha) which are critically involved in the onset and the development of CD. The present study was performed to explore the initial involvement of macrophages in the development of T-cell-mediated chronic colitis. METHODS: The effects were evaluated of saporin-conjugated anti-CD11b monoclonal antibody (mAb) on the development of chronic colitis in severe combined immunodeficiency (SCID) mice induced by adoptive transfer of CD4(+)CD45RB(high) T cells as an animal model of CD. RESULTS: Significantly increased CD11b-expressing macrophages as well as CD4(+) T cells were found in inflamed colon from colitic mice. Administration of saporin-conjugated anti-CD11b mAb markedly ameliorated the clinical and histopathological disease. In vivo treatment with saporin-conjugated anti-CD11b mAb decreased CD4(+) T-cell infiltration in the colon and suppressed interferon-gamma (IFN-gamma) and TNF-alpha production by lamina propria CD4(+) T cells. CONCLUSIONS: Collectively, the present results suggest an initial role of macrophages in the pathogenesis of T-cell-mediated chronic colitis. Furthermore, the macrophage-specific targeting may be a promising strategy for therapeutic intervention in CD.

TH1/TH2-mediated colitis induced by adoptive transfer of CD4+CD45RBhigh T lymphocytes into nude mice.

BACKGROUND: Transfer of CD4CD45RB T cells from normal donors to SCID/Rag-1, 2-deficient mice, which lack T and B cells, leads to the development of a TH1-mediated inflammatory bowel disease (IBD)-like syndrome characterized by extensive mononuclear cell infiltrates and epithelial cell hyperplasia. Because it is well known that B cells are also involved in a multitude of mechanistic pathways in human IBD, this study attempts to establish a new model of colitis in nude mice. METHODS: We transferred CD4CD45RB T cells into athymic nude mice, which lack thymus-dependent T cells but retain normal B cells, to establish and investigate a B cell-involving chronic colitis model. As a control, CD4CD25 T cells were also used. RESULTS: Mice reconstituted with CD4CD45RB but not CD4CD25 T cells developed a wasting disease, with severe infiltrates of B cell aggregates as well as T cells, macrophages, and dendritic cells into the colon and elevated levels of interferon-gamma, tumor necrosis factor-alpha, interleukin (IL)-4, IL-5, and IL-10, by 7 weeks after T cell transfer. Furthermore, the infiltrated lamina propria B cells in colitic nude mice consisted predominantly of massive aggregated immunoglobulin (Ig) M- and scattered IgG-positive cells, but not IgA-positive cells. In contrast, mice reconstituted with CD4CD45RB and CD4CD45RB did not develop wasting disease or colitis. CONCLUSIONS: Collectively, the power of the colitis model induced by the adoptive transfer of CD4CD45RB T cells into nude mice is that one can investigate the roles of TH2-type cells and B cells in a regulatory T cell-depleted condition.

Regulation of murine chronic colitis by CD4+CD25- programmed death-1+ T cells.

Naturally arising CD4(+)CD25(+) regulatory T (T(R)) cells are engaged in the maintenance of self tolerance and prevention of autoimmune diseases. However, accumulating evidence suggests that a fraction of peripheral CD4(+)CD25(-) T cells also possesses regulatory activity. Programmed death-1 (PD-1) is a new member of the CD28/CTLA-4 family, which has been implicated in the maintenance of peripheral self tolerance. Here, we identified a subpopulation of CD4(+)CD25(-)PD-1(+) T cells in the spleen of naive mice that constitutively expressed CTLA-4 and FoxP3 and was hypoproliferative in response to anti-CD3 antibody stimulation in vitro. However, the CD4(+)CD25(-)PD-1(+) T cells uniquely produced large amounts of IL-4 and IL-10 in response to anti-CD3 and anti-CD28 mAb stimulation, unlike the CD4(+)CD25(+) T(R) cells. The CD4(+)CD25(-)PD-1(+) T cells exhibited a suppressor activity against the proliferation of anti-CD3 antibody-stimulated CD4(+)CD25(-)PD-1(-) T cells in vitro, which was partially abrogated by anti-CTLA-4 mAb, but not by anti-IL-10 or anti-PD-1 mAb. Remarkably, the CD4(+)CD25(-)PD-1(+) T cells inhibited the development of colitis induced by adoptive transfer of CD4(+)CD45RB(high) T cells into C.B17-scid/scid mice, albeit to a lesser extent than CD4(+)CD25(+) T(R) cells, in a CTLA-4-dependent manner. These results indicate that the CD4(+)CD25(-)PD-1(+) T cells contain substantial amounts of T(R) cells that are involved in the maintenance of peripheral tolerance.

MyD88-deficient mice develop severe intestinal inflammation in dextran sodium sulfate colitis.

BACKGROUND: Gut commensal microbes affect the development and activation of the mucosal and systemic immune systems. However, the exact molecular mechanism of these microbes that is involved in the development of colitis remains unclear. METHODS: The present study was conducted to determine the distinct role of the innate immune system in the development of a dextran sulfate sodium (DSS) colitis model in MyD88(-/-) mice, because myeloid differentiation protein (MyD88) is a major adaptor molecule essential for signaling via Toll-like receptors (TLRs). To this end, MyD88(-/-) and wild-type (WT) mice received sterile distilled water containing 1.2% DSS for 8 days. The survival rate, total clinical score (body weight loss, stool consistency, and rectal bleeding), colon length, and histological score were assessed. The expression of surface markers (F4/80 and CD4) on infiltrating lamina propria mononuclear cells was analyzed immunohistochemistrically. RESULTS: MyD88(-/-) mice exhibited increased susceptibility to DSS-induced colitis, as reflected by significantly higher lethality and higher clinical and histological scores, and more severe colonic shortening compared to WT mice. Immunohistochemical analysis revealed a significant increase of both F4/80+ macrophages and CD4+ T cells in the inflamed mucosa in DSS-fed MyD88(-/-) mice compared to DSS-fed WT mice. CONCLUSIONS: These findings suggest that, via MyD88 signaling, the innate immune system in the gut plays an important protective role in colitis.

CD4+CD25bright T cells in human intestinal lamina propria as regulatory cells.

It is well known that immune responses in the intestine remain in a state of controlled inflammation, suggesting that not only active suppression by regulatory T cells plays an important role in the normal intestinal homeostasis, but also its dysregulation leads to the development of inflammatory bowel disease. In this study, we demonstrate that the CD4(+)CD25(bright) T cells reside in the human intestinal lamina propria (LP) and functionally retain regulatory activities. All human LP CD4(+) T cells regardless of CD25 expression constitutively expressed CTLA-4, glucocorticoid-induced TNFR family-related protein, and Foxp3 and proliferate poorly. Although LP CD4(+)CD25(-) T cells showed an activated and anergic/memory phenotype, they did not retain regulatory activity. In LP CD4(+)CD25(+) T cells, however, cells expressing CD25 at high levels (CD4(+)CD25(bright)) suppressed the proliferation and various cytokine productions of CD4(+)CD25(-) T cells. LP CD4(+)CD25(bright) T cells by themselves produced fewer amounts of IL-2, IFN-gamma, and IL-10. Interestingly, LP CD4(+)CD25(bright) T cells with regulatory T activity were significantly increased in patients with active inflammatory bowel disease. These results suggest that CD4(+)CD25(bright) T cells found in the normal and inflamed intestinal mucosa selectively inhibit the host immune response and therefore may contribute to the intestinal immune homeostasis.

Ectopic CD40 ligand expression on B cells triggers intestinal inflammation.

Several studies indicate that CD4(+) T cells, macrophages, and dendritic cells initially mediate intestinal inflammation in murine models of human inflammatory bowel disease. However, the initial role of B cells in the development of intestinal inflammation remains unclear. In this study we present evidence that B cells can trigger intestinal inflammation using transgenic (Tg) mice expressing CD40 ligand (CD40L) ectopically on B cells (CD40L/B Tg). We demonstrated that CD40L/B Tg mice spontaneously developed severe transmural intestinal inflammation in both colon and ileum at 8-15 wk of age. In contrast, CD40L/B TgxCD40(-/-) double-mutant mice did not develop colitis, indicating the direct involvement of CD40-CD40L interaction in the development of intestinal inflammation. The inflammatory infiltrates consisted predominantly of massive aggregated, IgM-positive B cells. These mice were also characterized by the presence of anti-colon autoantibodies and elevated IFN-gamma production. Furthermore, although mice transferred with CD4(+) T cells alone or with both CD4(+) T and B220(+) B cells, but not B220(+) cells alone, from diseased CD40L/B Tg mice, develop colitis, mice transferred with B220(+) B cells from diseased CD40L/B Tg mice and CD4(+) T cells from wild-type mice also develop colitis, indicating that the Tg B cells should be a trigger for this colitis model, whereas T cells are involved as effectors. As it has been demonstrated that CD40L is ectopically expressed on B cells in some autoimmune diseases, the present study suggests the possible contribution of B cells in triggering intestinal inflammation in human inflammatory bowel disease.

Blockade of B7-H1 suppresses the development of chronic intestinal inflammation.

A newly identified costimulatory molecule, programmed death-1 (PD-1), provides a negative signal that is essential for immune homeostasis. However, it has been suggested that its ligands, B7-H1 (PD-L1) and B7-dendritic cells (B7-DC; PD-L2), could also costimulate T cell proliferation and cytokine secretion. Here we demonstrate the involvement of PD-1/B7-H1 and B7-DC interaction in the development of colitis. We first examined the expression profiles of PD-1 and its ligands in both human inflammatory bowel disease and a murine chronic colitis model induced by adoptive transfer of CD4(+)CD45RB(high) T cells to SCID mice. Second, we assessed the therapeutic potential of neutralizing anti-B7-H1 and/or B7-DC mAbs using this colitis model. We found significantly increased expression of PD-1 on T cells and of B7-H1 on T, B, and macrophage/DCs in inflamed colon from both inflammatory bowel disease patients and colitic mice. Unexpectedly, the administration of anti-B7-H1, but not anti-B7-DC, mAb after transfer of CD4(+)CD45RB(high) T cells suppressed wasting disease with colitis, abrogated leukocyte infiltration, and reduced the production of IFN-gamma, IL-2, and TNF-alpha, but not IL-4 or IL-10, by lamina propria CD4(+) T cells. These data suggest that the interaction of PD-1/B7-H1, but not PD-1/B7-DC, might be involved in intestinal mucosal inflammation and also show a possible role of interaction between B7-H1 and an as yet unidentified receptor for B7-H1 in inducing T cell activation.

Macrophage-derived IL-18 targeting for the treatment of Crohn's disease.

Crohn's disease is an inflammatory bowel disease associated with several changes in the immune system, including an increased number of infiltrating macrophages. These macrophages release a variety of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha, macrophage infiltrating factor (MIF), interleukin (IL)-6, IL-12 and IL-18, which are critically involved in the onset and the development of Crohn's disease. We here focus on the role of macrophages, especially macrophage-derived IL-18 in both patients with Crohn's disease and a murine model of Crohn's disease.

Regulation of murine inflammatory bowel disease by CD25+ and CD25- CD4+ glucocorticoid-induced TNF receptor family-related gene+ regulatory T cells.

CD4(+)CD25(+) regulatory T cells in normal animals are engaged in the maintenance of immunological self-tolerance and prevention of autoimmune disease. However, accumulating evidence suggests that a fraction of the peripheral CD4(+)CD25(-) T cell population also possesses regulatory activity in vivo. Recently, it has been shown glucocorticoid-induced TNFR family-related gene (GITR) is predominantly expressed on CD4(+)CD25(+) regulatory T cells. In this study, we show evidence that CD4(+)GITR(+) T cells, regardless of the CD25 expression, regulate the mucosal immune responses and intestinal inflammation. SCID mice restored with the CD4(+)GITR(-) T cell population developed wasting disease and severe chronic colitis. Cotransfer of CD4(+)GITR(+) population prevented the development of CD4(+)CD45RB(high) T cell-transferred colitis. Administration of anti-GITR mAb-induced chronic colitis in mice restored both CD45RB(high) and CD45RB(low) CD4(+) T cells. Interestingly, both CD4(+)CD25(+) and CD4(+)CD25(-) GITR(+) T cells prevented wasting disease and colitis. Furthermore, in vitro studies revealed that CD4(+)CD25(-)GITR(+) T cells as well as CD4(+)CD25(+)GITR(+) T cells expressed CTLA-4 intracellularly, showed anergic, suppressed T cell proliferation, and produced IL-10 and TGF-beta. These data suggest that GITR can be used as a specific marker for regulatory T cells controlling mucosal inflammation and also as a target for treatment of inflammatory bowel disease.