Published papers

Background & Aims: Mucosal natural killer (NK) cells that produce interleukin (IL)-22 mediate intestinal homeostasis and inflammation in mice. However, their role in the pathogenesis of human inflammatory bowel diseases (IBDs) is not known. We investigated intestinal NK cells in intestinal mucosa samples of patients with Crohn's disease (CD). Methods: We isolated lamina propria NK cells from intestinal mucosal samples of patients with IBD and subjects without IBD (controls) and analyzed expression patterns of cell surface molecules and cytokine production. Interactions between lamina propria NK cells and intestinal macrophages were examined. Results: In intestinal mucosa samples from controls, NKp44 and NKp46 were expressed differentially on CD3 -CD56+ NK cells, NKp44+NKp46- (NKp44+) NK cells expressed CD127 and the transcription factor retinoic acid-related orphan receptor C (RORC) and produced IL-22 whereas NKp44-NKp46+ (NKp46+) NK cells did not express CD127 or RORC and produced interferon (IFN)-γ. NKp46+ NK cells were predominant in intestinal mucosa of patients with CD compared with controls or patients with ulcerative colitis. Upon interaction with intestinal inflammatory macrophages NKp46+, NK cells from patients with CD were activated via IL-23 and produced IFN-γ; this activation required cell-to-cell contact. Conclusions: The balance of NKp44+/NKp46 + NK cells is disrupted in intestinal mucosa of patients with CD. NKp46+ NK cells might mediate the pathogenesis of CD by producing IFN-γ. © 2010 by the AGA Institute.

Background: The endocytoscopy system (ECS) is a new method to provide real-time super-magnifying microscopic imaging in vivo. Routine diagnosis of amebic colitis requires multiple tests that are both time consuming and costly. Objective: To determine the feasibility of ECS to directly detect the amebic parasites in vivo. Design: Prospective, single-center, pilot study. Setting: Tertiary-care university hospital. Patients: This study involved 5 patients who were suspected to have amebic colitis by conventional colonoscopy in our institute. Interventions: A super-magnifying ECS with 450 × magnification. Main Outcome Measurements: We compared ECS findings with those of conventional methodsserum antibody tests and histology of colon biopsy specimens. Results: We successfully visualized the amebic trophozoites in all 5 cases. In contrast, 3 specimens had positive results on serology, and 3 had positive histology results on hematoxylin and eosin staining. Limitations: Pilot study with a limited number of patients. Findings were compared only with serology and histology findings. Conclusions: ECS would be a useful tool for the prompt diagnosis of amebic colitis via the real-time in vivo visualization of amebic trophozoites. © 2010 American Society for Gastrointestinal Endoscopy.

We have explored the pathological role of the MyD88 signaling pathway via Toll-like receptors (TLRs) that mediate the recognition of pathogen-associated molecular patterns (PAMPs) in a murine model of autoimmune hepatitis induced by administering Concanavalin A (ConA). We first found that various TLRs and MyD88 molecules were expressed in liver of Con A-treated and untreated wild-type (WT) mice including liver macrophages. Flowcytometric analysis revealed that liver CD11b+CD11c- and CD11b+CD11c+ antigen-presenting cells express TLR2, although NK and NKT cells did not. When WT and MyD88-/- mice were intravenously administered with Con A, the severity of hepatitis was significantly lower in Con A-injected MyD88-/- mice than in WT mice in terms of the histopathology, the levels of serum transaminase and pro-inflammatory cytokines (TNF-α, IFN-γ, and IL-6), and upregulation of CD80/CD86 and TNF-α on/in liver macrophages. The results provide evidence of a possible contribution of the TLRs-MyD88 signaling pathway in activating TLR-expressing liver macrophages in the autoimmune hepatitis model, and thus indicate that the strategy of blockade of pathological pathogens via the intestinal lumen may be feasible for the treatment of the disease. © 2010 Elsevier Inc.

Aim: Clinical symptoms are the most important factors used by physicians to evaluate the severity and extent of ulcerative colitis (UC). In this context, colonoscopy is also a useful diagnostic tool. We have recently developed an endoscopic activity index (EAI) to assess the severity of UC. Here, we assess the correlations among the EAI, other endoscopic indices, and clinical scores. The usefulness of the EAI for choosing treatment options, such as intravenous corticosteroid or cyclosporine A (CsA), in severe UC patients was also evaluated. Methods: Clinical symptoms and endoscopic finding were evaluated in 396 patients with UC (454 colonoscopies). The EAI was scored using the following six items: ulcer size, ulcer depth, redness, bleeding, edema, and mucus exudates. The patients were also scored using Matts' grade, Rachmilewitz's endoscopic index, and the Lichtiger index. Results: Our results showed that (1) the EAI scores were closely correlated with those of the Lichtiger index, Matts' grade, and Rachmilewitz's endoscopic index; (2) the EAI scores significantly decreased in patients who responded to treatment, while Matts' grade did not change in some responders treated with intravenous CsA and steroid; (3) patients with a higher EAI (14-16) tended to be refractory to corticosteroid therapy (responders 19%) compared to CsA (77%), while steroid treatment was effective in 58% of patients with EAI scores of 11-13. Conclusions: The EAI is equivalent to other endoscopic indices and relatively more useful in choosing a treatment for patients with severe UC. © 2010 Springer.

Background: Tumor necrosis factor (TNF)-like protein 1A (TL1A) is a member of the TNF superfamily and contributes to the pathogenesis of Crohn's disease (CD) by stimulating T-helper (Th) 1 cells. In addition to Th1, recent studies have focused on the role of Th17 cells in the pathogenesis of CD. Here we tried to clarify the role of TL1A in Th1 and Th17 immunity in CD. Methods: TL1A expression was assessed by quantitative reverse-transcription polymerase chain reaction (RT-PCR) in lamina propria (LP) macrophages (LP-Mφs) from normal controls (NC) and patients with CD or ulcerative colitis (UC). Purified LP CD4+ T cells were stimulated with TL1A and/or IL-23 and interferon gamma (IFN-γ) and interleukin (IL)-17 levels were analyzed. We also examined the effect of TL1A on naïve CD4+ Tcell differentiation. Results: We found that LP-Mφs are a major producer of TL1A. TL1A expression was markedly enhanced in LP-Mφs from CD patients compared with NC or UC patients. IL-23, in addition to TL1A, was induced in LP-Mφs by commensal bacteria stimulation. TL1A and IL-23 synergistically promoted the production of IFN-γ and IL-17 by LP T cells, while TL1A alone did not induce cytokine production. Furthermore, TL1A promoted Th17 differentiation from naïve T cells by LP-Mφs; however, IL-23 did not show any synergistic effects on Th17 differentiation. Conclusions: TL1A expressed in LP-Mφs might play an important role in the pathogenesis of CD by inducing Th1 and Th17 immunity. IL-23 differentially regulated these functions of TL1A on memory and naïve T cells. Copyright © 2009 Crohn's & Colitis Foundation of America, Inc.

Lamina propria macrophages (LPMφs) spontaneously produce large amounts of anti-inflammatory IL-10 and play a central role in regulation of immune responses against commensal bacteria. MCP-1 is a chemokine that plays an important role in recruitment of monocytes and macrophages to inflamed tissues. We demonstrated that, in addition to IL-10, LPMφs produced large amounts of MCP-1, even in a steady state. MCP-1 deficiency caused impaired IL-10 production by LPMφs and led to exacerbation of dextran sulfate sodium-induced acute colitis. As an explanation of this impaired IL-10 production by LPMφs, we found that LPMφs could be separated into two subsets with distinct side-scattered properties, namely LPMφ1 (CD11b+F4/80 +CD11c-SSChi) and LPMf2 (CD11b +F4/80+CD11c-SSClo). Unlike LPMφ1, the LPMφ2 subset migrated in response to MCP-1 and produced a larger amount of IL-10 in response to commensal bacteria. LPMφs isolated from MCP-1-deficient mice produced less IL-10 as a consequence of the lack of the MCP-1-dependent LPMφ2 population. This imbalanced composition in LPMφ population may be involved in the susceptibility to DSS-induced colitis in MCP-1-deficient mice. Our results suggest that endogenous MCP-1 contributes to the composition of resident LPMφ subsets in the intestine. Moreover, MCP-1-dependent LPMφ2 subset may play an important role in maintenance of gut homeostasis in the steady state, and in the termination of excess inflammatory responses in the intestine, by producing IL-10. Copyright © 2010 by The American Association of Immunologists, Inc.

Background: Musashi-1 (Msi-1) is a RNA-binding protein, known as a putative marker of intestinal stem cells (ISCs). However, little is known about the function of Msi-1 within human intestinal epithelial cells (IECs). Thus, the present study aimed to clarify the role of Msi-1 in differentiation and proliferation of IECs. Methods: A human intestinal epithelial cell line stably expressing Msi-1 was established. Proliferation of the established cell lines was measured by bromodeoxyuridine incorporation, whereas differentiation were assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of lineage-specific genes. Activities of the Notch and Wnt pathways were examined either by reporter assays or expression of downstream target genes. The distribution of Msi-1 and PLA2G2A expression in vivo was determined by immunohistochemistry. Results: Constitutive expression of Msi-1 in IECs had no significant effect on cell proliferation, but suppressed expression of Paneth cell-specific genes, including PLA2G2A. Msi-1 appeared to suppress expression of the PLA2G2A gene at the mRNA level. Analysis of Notch and Wnt pathway activity, however, revealed no significant change upon Msi-1 expression. The expression of Msi-1 and PLA2G2A in vivo was restricted to IECs residing at the lowest part of the human intestinal crypt, but was clearly separated to within basal columnar cells or mature Paneth cells, respectively. Conclusions: Msi-1 suppresses expression of Panethcell-specific genes in IECs, presumably through a pathway independent from Notch or Wnt. These findings suggest Msi-1 is a negative regulator of Paneth cell differentiation, an may contribute to maintain the undifferentiated phenotype of ISCs. © Springer 2009.

Background and Study Aims: Double-balloon endoscopy (DBE) is a new device that allows diagnosis and treatment throughout the entire small intestine. Although the originally described method requires two operators, we have recently developed a method to perform DBE by a single operator. We here assessed the clinical usefulness of this one-person method in comparison to the conventional two-person DBE. Patients and Methods: One hundred sixty-two patients (102 men and 60 women, mean age 59 years) underwent 303 DBE procedures. Total observation time, completion rate of total intestinal and colonic observation, lesion-discovery rate, and complication rate were retrospectively compared between the one-person method and the conventional two-person method of DBE. The one-person method consists of the Grip and Pinch technique and Keep (or Hold) and Slide technique. Results: The total observation times were 95.5 ± 35.1 min and 96.7 ± 47.5 min by one-person and two-person antegrade DBE, respectively, and 103 ± 29.8 min and 111 ± 30.1 min by one-person and two-person retrograde DBE, respectively. The completion rate for examination of the entire small intestine was 74.2% in one-person DBE and 76.5% in two-person DBE, respectively. The lesion-discovery rate was 69.0% in one-person DBE and 65.5% in two-person DBE, respectively. No significant differences between two methods were found in all measures. Also, no difference was observed in complication rate of the two methods. Conclusions: The single-operator method for DBE was as efficient as the dual-operator DBE without any higher risk of complications and, therefore, could replace the conventional dual-operator method in the future. © 2009 Journal of Gastroenterology and Hepatology Foundation and Blackwell Publishing Asia Pty Ltd.

Despite the advent of an age when "malignant" leukemia is cured by bone marrow transplantation, "benign" inflammatory bowel diseases (IBDs) are still intractable life-long 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. Copyright © 2008 Crohn's & Colitis Foundation of America, Inc.

Aim: Traditional herbal medicines have been used for several thousand years in China and other Asian countries. In this study we screened herbal drugs and their purified compounds, using the Feo replicon system, to determine their effects on in vitro HCV replication. Methods: We screened herbal drugs and their purified extracts for the activities to suppress hepatitis C virus (HCV) replication using an HCV replicon system that expressed chimeric firefly luciferase reporter and neomycin phosphotransferase (Feo) genes. We tested extracts and 13 purified compounds from the following herbs: Glycyrrhizae radix; Rehmanniae radix; Paeoniae radix; Artemisiae capillari spica; and Rhei rhizoma. Results: The HCV replication was significantly and dose-dependently suppressed by two purified compounds, isoliquiritigenin and glycycoumarin, which were from Glycyrrhizae radix. Dose-effect analyses showed that 50% effective concentrations were 6.2 ± 1.0 μg/mL and 15.5 ± 0.8 μg/mL for isoliquiritigenin and glycycoumarin, respectively. The MTS assay did not show any effect on cell growth and viability at these effective concentrations, indicating that the effects of the two compounds were specific to HCV replication. These two compounds did not affect the HCV IRES-dependent translation nor did they show synergistic action with interferon-alpha. Conclusion: Two purified herbal extracts, isoliquiritigenin and glycycoumarin, specifically suppressed in vitro HCV replication. Further elucidation of their mechanisms of action and evaluation of in vivo effects and safety might constitute a new anti-HCV therapeutics. © 2009 The Japan Society of Hepatology.

Inflammatory bowel diseases (IBD) are thought to be caused by a complex interaction of genetic, immunological, and environmental factors. Why is it that once an IBD develops it lasts a long time? Considering this simple question, we propose that coliotogenic memory CD4+T cells that remember the prototype of the disease in each patient are formed in IBD at the onset, and, perceiving them as "benign T-cell leukemia"-like lifelong memory CD4+T cells that hematogenously spread throughout the body, we thus propose that systemic circulating colitogenic memory CD4+T cells would be an ideal target for the treatment of IBD. Accordingly, selective depletion of colitogenic memory CD4+T cells by leukocytapheresis and blockade of circulation of colitogenic memory CD4+T cells by a newly developed immunosuppressant, FTY720, may be associated with dramatic efficacy and a marked reduction of inflammatory cytokines produced by activated leucocytes. We here describe the immunological pathogenesis focusing on the generation of circulating colitogenic memory CD4+T cells and the possible logics of leukocytapheresis and FTY720 for the treatment of IBD.

We previously demonstrated that IL-7 is essential for the persistence of T-cell-mediated colitis, by showing that adoptive transfer of CD4 +CD45RBhigh 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. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.

To understand the perpetuation of inflammatory bowel disease (IBD), it is important to clarify whether the colitogenic CD4+ T cells are self-limited effector or long-lived memory T cells. We here investigate the latency of colitogenic CD4+ T cells in the remission stage of colitis under germfree (GF) conditions. We isolated splenic (SP) CD4+ T cells from colitic CD4+CD45RBhigh T cell-injected SCID mice maintained under specific pathogen-free (SPF) conditions and transferred them into SPF or GF SCID mice. Donor colitic SP CD4+ T cells have a characteristic CD44highCD62L-IL-7Rαhigh effector-memory T-type phenotype. Six weeks after transfer of cells to GF SCID mice, one group of mice was continued in GF conditions (GF→GF), and the other was transferred into SPF conditions (GF→SPF). GF→SPF but not GF→GF SCID mice developed colitis with elevated production of Th1 and Th17 cytokines at 4 wk after transfer. Surprisingly, a large number of CD4 + effector-memory T cells and a small but substantial number of central-memory T cells remained resident in SP and bone marrow, but not in lamina propria, of the GF→GF SCID recipients. Consistent with this, GF3SPF but not GF→GF SCID mice rapidly developed colitis. Taken together, these findings suggest that long-lived colitogenic memory CD4+ cells can be established even in the presence of commensal Ags, reside outside the intestine in the absence of commensal bacteria, and participate in the perpetuation of colitis. Thus, blocking a stimulus of colitogenic memory CD4+ cells such as IL-7 may have therapeutic benefit for treatment of inflammatory bowel disease. Copyright © 2009 by The American Association of Immunologists, Inc.

Intestinal APCs are considered critical in maintaining the balance between the response against harmful pathogens and the induction of tolerance to commensal bacteria and food Ags. Recently, several studies indicated the presence of gut-specific APC subsets, which possess both macrophage and dendritic cell (DC) markers. These unique APC subsets play important roles in gut immunity, especially for immune regulation against commensal bacteria. Herein, we examined a unique macrophage subset, which coexpressed the macrophage (Mφ) marker CD14 and the DC marker CD209 in human intestinal lamina propria (LP). The LP Mφ subset in both normal control subjects or Crohn's disease (CD) patients induced proliferation of naive CD4+ T cells as well as monocyte-derived DCs, and it expressed retinoic acid synthetic enzyme retinaldehyde dehydrogenase 2 and retinol dehydrogenase 10, which induced expression of gut homing receptors on T cells in a retinoic acid-dependent manner. Moreover, the LP Mφ subset strongly evoked differentiation of Th1 cells and slightly induced Th17 cells in both normal control subjects and CD patients; the inducing potential was highest in CD patients. In CD patients, Th17, but not Th1, induction by the LP Mφ subset was enhanced in the presence of commensal bacteria Ags. This enhancement was not observed in normal control subjects. The Th17 induction by the LP Mφ subset was inhibited by neutralization of IL-6 and IL-1β, but it was enhanced by blockade of retinoic acid signaling. These observations highlight a role for LPMφ in the enhanced Th1, and potentially in Th17 differentiation, at the inflammatory site of inflammatory bowel diseases. Copyright © 2009 by The American Association of Immunologists, Inc.

Lippincott Williams & Wilkins.Purpose of review: This review focuses on CD4+ T cells involved in the mediation of inflammatory tissue damage in murine models of inflammatory bowel diseases (IBDs). In particular, we describe the distinct roles of the homeostatic cytokine IL-7, which is essential to the maintenance of colitogenic memory CD4+ cells, and the newly discovered effector cytokine IL-17. We also discuss the close correlation between colitogenic Th17-type CD4 + T cells and inducible CD4+CD25+Foxp3 + regulatory T cells. Recent findings: IBDs are characterized by wasting and chronic intestinal inflammation induced by many different cytokine-mediated pathways. It is clearly recognized that medical and surgical interventions do not cure Crohn's disease because relapse is the rule after remission. Until a few years ago, IBD was classified into Th1-dependent, that is, Crohn's disease, and Th2-dependent, that is, ulcerative colitis, phenotypes. However, in recent years, it has been shown that new T-cell subclasses, that is, Th17 and regulatory T cells (TR), exist independently of Th1 and Th2 and that they play a central role in modulating IBD. Summary: The persistence of IL-7-dependent colitogenic memory CD4+ T cells is critical to the maintenance of experimental colitis. On the other hand, though Th1 and Th2 colitogenic memory CD4+ cells exist, in recent years the central role of IL-17-producing Th17-type cells in IBD has attracted renewed interest. The development of molecularly targeted therapies aimed at a variety of different Th-dependent pathogenic mechanisms may represent a novel approach to IBD therapy. © 2009 Wolters Kluwer Health

It is now clear that functional CD4+CD25+ regulatory T (TR) cells exist as part of the normal immune population and prevent the development of intestinal inflammation. We have recently shown that CD4+CD25+ TR 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+ TR 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+ TR cells to suppress the proliferation of CD4+ responder cells in vitro, in vivo administration of anti-RANKL mAb abrogated CD4+CD25+ TR cell-mediated suppression of colitis induced by adoptive transfer of CD4+CD45RBhigh T cells into SCID mice. Interestingly, an adoptive transfer experiment using Ly5.1+CD4 +CD45RBhigh cells and Ly5.2+CD4 +CD25+ TR cells revealed that the ratio of CD4+CD25+ TR 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+ TR 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+ TR cells in colitis. Copyright © 2009 by The American Association of Immunologists, Inc.

Treatment with anti-TNF-α 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-α signaling in epithelial cells is involved in the development of CAC. To investigate this, we studied the effects of anti-TNF-α 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-κB 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-κB activation is further complicated in CAC tissues induced in AOM/DSS-administered mice compared with the nontumor area. Such NF-κB activity in the epithelial cells is significantly suppressed by the treatment of MP6-XT22, an anti-TNF-α 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-κB 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-α MAb may prevent the development of CAC in patients with long-standing IBD. Copyright © 2009 the American Physiological Society.

Notch signaling regulates cell differentiation and proliferation, contributing to the maintenance of diverse tissues including the intestinal epithelia. However, its role in tissue regeneration is less understood. Here, we show that Notch signaling is activated in a greater number of intestinal epithelial cells in the inflamed mucosa of colitis. Inhibition of Notch activation in vivo using a γ-secretase inhibitor resulted in a severe exacerbation of the colitis attributable to the loss of the regenerative response within the epithelial layer. Activation of Notch supported epithelial regeneration by suppressing goblet cell differentiation, but it also promoted cell proliferation, as shown in in vivo and in vitro studies. By utilizing tetracycline-dependent gene expression and microarray analysis, we identified a novel group of genes that are regulated downstream of Notch1 within intestinal epithelial cells, including PLA2G2A, an antimicrobial peptide secreted by Paneth cells. Finally, we show that these functions of activated Notch1 are present in the mucosa of ulcerative colitis, mediating cell proliferation, goblet cell depletion, and ectopic expression of PLA2G2A, thereby contributing to the regeneration of the damaged epithelia. This study showed the critical involvement of Notch signaling during intestinal tissue regeneration, regulating differentiation, proliferation, and antimicrobial response of the epithelial cells. Thus Notch signaling is a key intracellular molecular pathway for the proper reconstruction of the intestinal epithelia. Copyright © 2009 the American Physiological Society.

Background: Chronic inflammatory diseases are characterized by massive infiltration of innate and acquired immune cells in inflammatory sites. However, it remains unclear how these cells cooperate in the development of disease. Although bone marrow (BM) is a primary site for hematopoiesis of immune cells except T cells, BM recruits memory T cells from the periphery. We have recently demonstrated that colitogenic CD4+ memory T cells reside in BM of colitic CD4+CD45RBhigh T-cell-transferred SCID mice. Based on this background we here investigate whether granulocytes promote or suppress the expansion of colitogenic CD4+ T cells. Methods: First, we show that Gr-1highCD11b+ granulocytes were significantly increased in colitic BM along with a significant increase of peripheral granulocytes. Consistently, the colony-forming unit (CFU) assay revealed that granulocyte colony formation was dominantly induced by supernatants from anti-CD3-stimulated colitic BM CD4+ T cells. Results: Administration of granulocyte-depleting anti-Gr-1 mAb to colitic mice did not ameliorate the colitis, but exacerbated the wasting disease with an increased expansion of systemic, but not lamina propria, CD4+ T cells with activated phenotype. Conclusions: These results suggest that the increased granulopoiesis by colitogenic BM CD4+ T cells represent a negative feedback mechanism to control systemic inflammation. Copyright © 2008 Crohn's & Colitis Foundation of America, Inc.