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

Targeting TNF/TNFR superfamilies in immune-mediated inflammatory diseases

Dysregulated signaling from TNF and TNFR proteins is implicated in several immune-mediated inflammatory diseases (IMIDs). This review centers around seven IMIDs (rheumatoid arthritis, systemic lupus erythematosus, Crohn's disease, ulcerative colitis, psoriasis, atopic dermatitis, and asthma) with substantial unmet medical needs and sheds light on the signaling mechanisms, disease relevance, and evolving drug development activities for five TNF/TNFR signaling axes that garner substantial drug development interest in these focus conditions. The review also explores the current landscape of therapeutics, emphasizing the limitations of the approved biologics, and the opportunities presented by small-molecule inhibitors and combination antagonists of TNF/TNFR signaling.

The Cyclin-Dependent Kinase 8 (CDK8) Inhibitor DCA Promotes a Tolerogenic Chemical Immunophenotype in CD4+ T Cells via a Novel CDK8-GATA3-FOXP3 Pathway

Immune health requires innate and adaptive immune cells to engage precisely balanced pro- and anti-inflammatory forces. We employ the concept of chemical immunophenotypes to classify small molecules functionally or mechanistically according to their patterns of effects on primary innate and adaptive immune cells. The high-specificity, low-toxicity cyclin-dependent kinase 8 (CDK8) inhibitor 16-didehydro-cortistatin A (DCA) exerts a distinct tolerogenic profile in both innate and adaptive immune cells. DCA promotes regulatory T cells (Treg) and Th2 differentiation while inhibiting Th1 and Th17 differentiation in both murine and human cells. This unique chemical immunophenotype led to mechanistic studies showing that DCA promotes Treg differentiation in part by regulating a previously undescribed CDK8-GATA3-FOXP3 pathway that regulates early pathways of Foxp3 expression. These results highlight previously unappreciated links between Treg and Th2 differentiation and extend our understanding of the transcription factors that regulate Treg differentiation and their temporal sequencing. These findings have significant implications for future mechanistic and translational studies of CDK8 and CDK8 inhibitors.

Shedding Light on Hemostasis in Patients With Inflammatory Bowel Diseases

Patients with inflammatory bowel diseases (IBD) have an increased risk of thrombosis, possibly due to changes in blood cells and molecules involved in hemostasis. They have increased platelet counts and reactivity as well as increased platelet-derived large extracellular vesicles. Coagulation is continuously activated in patients with IBD, based on measured markers of thrombin generation, and the anticoagulant functions of endothelial cells are damaged. Furthermore, fibrinogen is increased and fibrin clots are denser. However, pathogenesis of thrombosis in patients with IBD appears to differ from that of patients without IBD. Patients with IBD also take drugs that might contribute to risk of thrombosis, complicating the picture. We review the features of homeostasis that are altered in patients with IBD and possible mechanisms of this relationship.

Molecular basis and therapeutic implications of CD40/CD40L immune checkpoint

The CD40 receptor and its ligand CD40L is one of the most critical molecular pairs of the stimulatory immune checkpoints. Both CD40 and CD40L have a membrane form and a soluble form generated by proteolytic cleavage or alternative splicing. CD40 and CD40L are widely expressed in various types of cells, among which B cells and myeloid cells constitutively express high levels of CD40, and T cells and platelets express high levels of CD40L upon activation. CD40L self-assembles into functional trimers which induce CD40 trimerization and downstream signaling. The canonical CD40/CD40L signaling is mediated by recruitment of TRAFs and NF-κB activation, which is supplemented by signal pathways such as PI3K/AKT, MAPKs and JAK3/STATs. CD40/CD40L immune checkpoint leads to activation of both innate and adaptive immune cells via two-way signaling. CD40/CD40L interaction also participates in regulating thrombosis, tissue inflammation, hematopoiesis and tumor cell fate. Because of its essential role in immune activation, CD40/CD40L interaction has been regarded as an attractive immunotherapy target. In recent years, significant advance has been made in CD40/CD40L-targeted therapy. Various types of agents, including agonistic/antagonistic monoclonal antibodies, cellular vaccines, adenoviral vectors and protein antagonist, have been developed and evaluated in early-stage clinical trials for treating malignancies, autoimmune diseases and allograft rejection. In general, these agents have demonstrated favorable safety and some of them show promising clinical efficacy. The mechanisms of benefits include immune cell activation and tumor cell lysis/apoptosis in malignancies, or immune cell inactivation in autoimmune diseases and allograft rejection. This review provides a comprehensive overview of the structure, processing, cellular expression pattern, signaling and effector function of CD40/CD40L checkpoint molecules. In addition, we summarize the progress, targeted diseases and outcomes of current ongoing and completed clinical trials of CD40/CD40L-targeted therapy.

Activation of Cannabinoid Receptor 2 Prevents Colitis-Associated Colon Cancer through Myeloid Cell De-activation Upstream of IL-22 Production

Intestinal disequilibrium leads to inflammatory bowel disease (IBD), and chronic inflammation predisposes to oncogenesis. Antigen-presenting dendritic cells (DCs) and macrophages can tip the equilibrium toward tolerance or pathology. Here we show that delta-9-tetrahydrocannabinol (THC) attenuates colitis-associated colon cancer and colitis induced by anti-CD40. Working through cannabinoid receptor 2 (CB2), THC increases CD103 expression on DCs and macrophages and upregulates TGF-β1 to increase T regulatory cells (Tregs). THC-induced Tregs are necessary to remedy systemic IFNγ and TNFα caused by anti-CD40, but CB2-mediated suppression of APCs by THC quenches pathogenic release of IL-22 and IL-17A in the colon. By examining tissues from multiple sites, we confirmed that THC affects DCs, especially in mucosal barrier sites in the colon and lungs, to reduce DC CD86. Using models of colitis and systemic inflammation we show that THC, through CB2, is a potent suppressor of aberrant immune responses by provoking coordination between APCs and Tregs.

The enhanced immunopharmacology of VIB4920, a novel Tn3 fusion protein and CD40L antagonist, and assessment of its safety profile in cynomolgus monkeys

BACKGROUND AND PURPOSE

Inhibition of the T- and B-cell interaction through the CD40/CD40 ligand (L) axis is a favourable approach for inflammatory disease treatment. Clinical studies of anti-CD40L molecules in autoimmune diseases have met challenges because of thromboembolic events and adverse haemostasis. VIB4920 (formerly MEDI4920) is a novel CD40L antagonist and Tn3 fusion protein designed to prevent adverse haemostasis and immunopharmacology. We evaluated the pharmacokinetics, activity and toxicity of VIB4920 in monkeys.

EXPERIMENTAL APPROACH

Cynomolgus monkeys received i.v. or s.c. 5-300 mg·kg^-1 VIB4920 or vehicle, once weekly for 1 month (Studies 1 and 2) or 28 weeks (Study 3). VIB4920 exposure and bioavailability were determined using pharmacokinetic analyses, and immune cell population changes via flow cytometry. Pharmacological activity was evaluated by measuring the animals' capacity to elicit an immune response to keyhole limpet haemocyanin (KLH) and tetanus toxoid (TT).

KEY RESULTS

VIB4920 demonstrated linear pharmacokinetics at multiple doses. Lymphocyte, monocyte, cytotoxic T-cell and NK cell counts were not significantly different between treatment groups. B-cell counts reduced dose-dependently and the T-cell dependent antibody response to KLH was suppressed by VIB4920 dose-dependently. The recall response to TT was similar across treatment groups. No thromboembolic events or symptoms of immune system dysfunctionality were observed.

CONCLUSIONS AND IMPLICATIONS

VIB4920 demonstrated an acceptable safety profile in monkeys. VIB4920 showed favourable pharmacokinetics, dose-dependent inhibition of a neoantigen-specific immune response and no adverse effects on immune function following long-term use. Our data support the use of VIB4920 in clinical trials.

CD4 T cells are required for both development and maintenance of disease in a new mouse model of reversible colitis

Current therapies to treat inflammatory bowel diseases have limited efficacy, significant side effects, and often wane over time. Little is known about the cellular and molecular mechanisms operative in the process of mucosal healing from colitis. To study such events, we developed a new model of reversible colitis in which adoptive transfer of CD4(+)CD45RB(hi) T cells into Helicobacter typhlonius-colonized lymphopenic mice resulted in a rapid onset of colonic inflammation that was reversible through depletion of colitogenic T cells. Remission was associated with an improved clinical and histopathological score, reduced immune cell infiltration to the intestinal mucosa, altered intestinal gene expression profiles, regeneration of the colonic mucus layer, and the restoration of epithelial barrier integrity. Notably, colitogenic T cells were not only critical for induction of colitis but also for maintenance of disease. Depletion of colitogenic T cells resulted in a rapid drop in tumor necrosis factor α (TNFα) levels associated with reduced infiltration of inflammatory immune cells to sites of inflammation. Although neutralization of TNFα prevented the onset of colitis, anti-TNFα treatment of mice with established disease failed to resolve colonic inflammation. Collectively, this new model of reversible colitis provides an important research tool to study the dynamics of mucosal healing in chronic intestinal remitting-relapsing disorders.

Methods of Inducing Inflammatory Bowel Disease in Mice

Animal models of experimentally induced inflammatory bowel disease (IBD) are useful for understanding more about the mechanistic basis of the disease, identifying new targets for therapeutic intervention, and testing novel therapeutics. This unit provides detailed protocols for five widely used mouse models of experimentally induced intestinal inflammation: chemical induction of colitis by dextran sodium sulfate (DSS), hapten-induced colitis via 2,4,6-trinitrobenzene sulfonic acid (TNBS), Helicobacter-induced colitis in mdr1a(-/-) mice, the CD4(+) CD45RB(hi) SCID transfer colitis model, and the IL-10(-/-) colitis model. © 2016 by John Wiley & Sons, Inc.

The kinase DYRK1A reciprocally regulates the differentiation of Th17 and regulatory T cells

The balance between Th17 and T regulatory (Treg) cells critically modulates immune homeostasis, with an inadequate Treg response contributing to inflammatory disease. Using an unbiased chemical biology approach, we identified a novel role for the dual specificity tyrosine-phosphorylation-regulated kinase DYRK1A in regulating this balance. Inhibition of DYRK1A enhances Treg differentiation and impairs Th17 differentiation without affecting known pathways of Treg/Th17 differentiation. Thus, DYRK1A represents a novel mechanistic node at the branch point between commitment to either Treg or Th17 lineages. Importantly, both Treg cells generated using the DYRK1A inhibitor harmine and direct administration of harmine itself potently attenuate inflammation in multiple experimental models of systemic autoimmunity and mucosal inflammation. Our results identify DYRK1A as a physiologically relevant regulator of Treg cell differentiation and suggest a broader role for other DYRK family members in immune homeostasis. These results are discussed in the context of human diseases associated with dysregulated DYRK activity.

Classical Th1 cells obtain colitogenicity by co-existence of RORγt-expressing T cells in experimental colitis

BACKGROUND

Both Th1 and Th17 cell types are involved in the pathogenesis of chronic intestinal inflammation. We recently demonstrated that retinoid-related orphan receptor gamma t (RORγt)-expressing Th17 cells are progenitor cells for alternative Th1 cells, which have the potential to induce colitis. However, the involvement of classical Th1 (cTh1) cells generated directly from naive T cells without RORγt expression in the pathogenesis of colitis remains poorly understood.

METHODS

We performed a series of in vivo experiments using a murine chronic colitis model induced by adoptive transfer of splenic CD4CD45RB(high) T cells obtained from wild-type, RORγt(gfp/gfp), or RORγt(gfp/gfp) mice into RAG-2(-/-) mice.

RESULTS

RAG-2(-/-) mice receiving transfer of in vitro-manipulated RORγt(gfp/gfp) Th1 cells developed colitis. RAG-2(-/-) mice co-transferred with splenic CD4CD45RB(high) T cells obtained from wild-type mice and RORγt(gfp/gfp) mice developed colitis with a significant increase in RORγt cTh1 cell numbers when compared with noncolitic mice transferred with splenic CD4CD45RB(high) T cells obtained from RORγt(gfp/gfp) mice. Furthermore, RAG-2(-/-) mice transferred with in vivo-manipulated RORγt(gfp/gfp) cTh1 cells developed colitis with a significant increase in RORγt(gfp/gfp) cTh1 cell numbers.

CONCLUSIONS

These findings indicate that both alternative Th1 cells and cTh1 cells have the potential to be colitogenic in an adaptive transfer model. The development of cTh1 cells was dependent on the co-existence of RORγt-expressing T cells, suggesting a critical role for the interactions of these cell types in the development of chronic intestinal inflammation.

Dendritic cells administered intrarectally penetrate the intestinal barrier to break intestinal tolerance via Th2-medeiated colitis in mice

Intestinal lamina propria dendritic cells (LPDCs) in mice are known to extend dendrites between the intestinal epithelia and the luminal side when processing luminal antigens. We conducted intrarectal cell transfer experiments of bone marrow-derived dendritic cells (BMDCs) in mice to assess dendritic cell penetration of the intestine. Intrarectally administered GFP(+) BMDCs localized in the colonic LP within 3h and the spleen within 12h after administration. 72h after administration, recipient C57BL/6 mice showed acute diarrhea, and administration of BMDCs (once weekly for 3 weeks) induced intestinal inflammation with increased numbers of recipient macrophages and CD4(+) T cells exhibiting a Th2-mediated immune response. These results demonstrate that DCs actively communicate across the intestinal barrier, and highlight a potential technique for controlling colonic immune tolerance.

Circulatory antigen processing by mucosal dendritic cells controls CD8(+) T cell activation

Circulatory antigens transit through the small intestine via the fenestrated capillaries in the lamina propria prior to entering into the draining lymphatics. But whether or how this process controls mucosal immune responses remains unknown. Here we demonstrate that dendritic cells (DCs) of the lamina propria can sample and process both circulatory and luminal antigens. Surprisingly, antigen cross-presentation by resident CX3CR1(+) DCs induced differentiation of precursor cells into CD8(+) T cells that expressed interleukin-10 (IL-10), IL-13, and IL-9 and could migrate into adjacent compartments. We conclude that lamina propria CX3CR1(+) DCs facilitate the surveillance of circulatory antigens and act as a conduit for the processing of self- and intestinally absorbed antigens, leading to the induction of CD8(+) T cells, that partake in the control of T cell activation during mucosal immune responses.

Signaling lymphocyte activation molecule regulates development of colitis in mice

BACKGROUND & AIMS

Signaling lymphocyte activation molecule (Slamf)1 is a co-stimulatory receptor on T cells and regulates cytokine production by macrophages and dendritic cells. Slamf1 regulates microbicidal mechanisms in macrophages, therefore we investigated whether the receptor affects development of colitis in mice.

METHODS

We transferred CD45RB(hi) CD4(+) T cells into Rag(-/-) or Slamf1(-/-)Rag(-/-) mice to induce colitis. We also induced colitis by injecting mice with an antibody that activates CD40. We determined the severity of enterocolitis based on disease activity index, histology scores, and levels of cytokine production, and assessed the effects of antibodies against Slamf1 on colitis induction. We quantified migration of monocytes and macrophage to inflamed tissues upon induction of colitis or thioglycollate-induced peritonitis and in response to tumor necrosis factor-α in an air-pouch model of leukocyte migration.

RESULTS

Colitis was reduced in Slamf1(-/-)Rag(-/-) mice, compared with Rag(-/-) mice, after transfer of CD45RB(hi) CD4(+) T cells or administration of the CD40 agonist. The numbers of monocytes and macrophages were reduced in inflamed tissues of Slamf1(-/-)Rag(-/-) mice, compared with Rag(-/-) mice, after induction of colitis and other inflammatory disorders. An antibody that inhibited Slamf1 reduced the level of enterocolitis in Rag(-/-) mice.

CONCLUSIONS

Slamf1 contributes to the development of colitis in mice. It appears to indirectly regulate the appearance of monocytes and macrophages in inflamed intestinal tissues. Antibodies that inhibit Slamf1 reduce colitis in mice, so human SLAMF1 might be a therapeutic target for inflammatory bowel disease.

Aberrant accumulation of interleukin-10-secreting neutrophils in TRAF2-deficient mice

Highly coordinated expression of inflammatory and anti-inflammatory cytokines is crucial for maintaining homeostasis of the gut that is constantly exposed to large amounts of commensal bacteria. We have previously reported that tumor necrosis factor (TNF) receptor-associated factor (Traf)2(-/-) mice spontaneously develop severe colitis and that the development of colitis largely depends on TNFα-dependent apoptosis of colonic epithelial cells. However, the detailed molecular mechanisms underlying the immunological disorders of Traf2(-/-) mice are not fully understood. Here we show that interleukin (IL)-10-secreting neutrophils accumulated in peripheral blood and bone marrow (BM) cells from Traf2(-/-) mice compared with those from wild-type mice. Treatment of Traf2(-/-) mice with neutralizing antibody against TNFα or crossing Traf2(-/-) mice with Tnfr1(-/-) mice reduced the percentages of IL-10-secreting neutrophils, suggesting that the development of IL-10-secreting neutrophils largely depended on TNFα signals. Moreover, stimulation of BM cells from wild-type mice with lipopolysaccharide and Pam3CS(K)4, a ligand for Toll-like receptor 4 and 2, respectively, induced differentiation of BM cells into IL-10-secreting neutrophils. These results suggest that the development of IL-10-secreting neutrophils is not restricted to Traf2(-/-) mice, but could be generalized to wild-type mice under certain conditions such as inflammation. Finally, combined treatment of Traf2(-/-) mice with neutralizing antibodies against TNFα and IL-10, but not each antibody alone, substantially ameliorated colitis and prolonged survival. Together, abrogation of immunosuppressive conditions mediated by IL-10-secreting neutrophils might be an alternative strategy to treat chronic inflammatory diseases at least under certain conditions.

Fine-tuning of dendritic cell biology by the TNF superfamily

Members of the tumour necrosis factor (TNF) superfamily have been implicated in a wide range of biological functions, and their expression by cells of the immune system makes them appealing targets for immunomodulation. One common theme for TNF superfamily members is their coordinated expression at the interface between antigen-specific T cells and antigen-presenting dendritic cells and, by virtue of this expression pattern, TNF superfamily members can shape T cell immune responses. Understanding how to manipulate such functions of the TNF superfamily may allow us to tip the balance between immunity and tolerance in the context of human disease.

Methods of inducing inflammatory bowel disease in mice

Animal models of experimentally induced inflammatory bowel disease (IBD) are useful for understanding more about the mechanistic basis of disease, identifying new targets for therapeutic intervention, and testing novel therapeutic agents. This unit provides detailed protocols for four of the most commonly used mouse models of experimentally induced intestinal inflammation: chemical induction of colitis by dextran sodium sulfate (DSS), hapten-induced colitis via 2,4,6-trinitrobenzene sulfonic acid (TNBS), Helicobacter-induced colitis in mdr1a(-/-) mice, and the CD4(+) CD45RB(hi) SCID transfer colitis model.

Variable impact of CD39 in experimental murine colitis

BACKGROUND

Dysregulation of immune responses in inflammatory bowel diseases (IBD) results in intestinal inflammation and vascular injury while exacerbating systemic disease. CD39 is an ectonucleotidase, expressed by T regulatory cells and dendritic cells, that hydrolyzes extracellular nucleotides to modify those cellular immune responses implicated in IBD. Genetic polymorphisms of CD39 have been linked to Crohn's disease while gene deletion in mice exacerbates dextran sodium sulphate-induced colitis.

AIM

The aim of this study was to test how global deletion of CD39 in mice impacts other models of experimental colitis.

METHODS

Colitis was induced in CD39-null and -wt mice, using trinitrobenzene sulfonic acid (TNBS, 125 mg/kg) administered intrarectally. Oxazolone colitis (1.5% oxazolone in 50% alcohol) was induced in comparable groups. Morphology, clinical and molecular parameters, and FACS analyses of lamina propria mononuclear cells (LPMC) were examined in CD39-null mice. CD39 expression was analyzed in human IBD biopsies.

RESULTS

Paradoxically, TNBS colitis in CD39-null mice was characterized by improved survival, favorable clinical scores, and decreased MPO activity, when compared to wt mice (P < 0.05). LPMC from TNBS colitis contained significantly increased amounts of T-cells (CD3(+) and CD4(+)) and TNF-α mRNA expression were increased over those in CD39 null mice (P < 0.05). In contrast, oxazolone treated CD39-null and wt mice had comparable outcomes. In both ulcerative colitis and Crohn's disease, CD39 is present at high levels in intestinal tissue biopsies.

CONCLUSIONS

TNBS colitis was attenuated in CD39-null mice whereas oxazolone-induced colitis was not impacted. Impaired adaptive cellular immune reactivity in the CD39-null environment appears protective in hapten-mediated Th1-type colitis. CD39 is expressed at high levels in clinical IBD tissues.

Tumor necrosis factor receptor-associated factor (TRAF) 2 controls homeostasis of the colon to prevent spontaneous development of murine inflammatory bowel disease

Fine-tuning of host cell responses to commensal bacteria plays a crucial role in maintaining homeostasis of the gut. Here, we show that tumor necrosis factor receptor-associated factor (Traf)2(-/-) mice spontaneously developed severe colitis and succumbed within 3 weeks after birth. Histological analysis revealed that apoptosis of colonic epithelial cells was enhanced, and B cells diffusely infiltrated into the submucosal layer of the colon of Traf2(-/-) mice. Expression of proinflammatory cytokines, including Tnfa, Il17a, and Ifng, was up-regulated, whereas expression of antimicrobial peptides was down-regulated in the colon of Traf2(-/-) mice. Moreover, a number of IL-17-producing helper T cells were increased in the colonic lamina propria of Traf2(-/-) mice. These cellular alterations resulted in drastic changes in the colonic microbiota of Traf2(-/-) mice compared with Traf2(+/+) mice. Treatment of Traf2(-/-) mice with antibiotics ameliorated colitis along with down-regulation of proinflammatory cytokines and prolonged survival, suggesting that the altered colonic microbiota might contribute to exacerbation of colitis. Finally, deletion of Tnfr1, but not Il17a, dramatically ameliorated colitis in Traf2(-/-) mice by preventing apoptosis of colonic epithelial cells, down-regulation of proinflammatory cytokines, and restoration of wild-type commensal bacteria. Together, TRAF2 plays a crucial role in controlling homeostasis of the colon.

Involvement of CD40-CD40 ligand in uncomplicated and refractory celiac disease

OBJECTIVES

Cognate interaction between CD40 on antigen-presenting cells and CD40 ligand (CD40L) on T cells is a crucial costimulatory signal in T-cell activation. In this study, we investigated CD40-CD40L expression in the duodenum of uncomplicated and refractory celiac disease patients, and explored the ex vivo effects of CD40L blockade on cytokine production and the T-helper cell type 1-specific transcription factor T-bet.

METHODS

CD40L and colocalization of CD40 with the dendritic cell markers CD11c and CD123 were investigated by confocal microscopy on tissue sections of duodenal biopsy samples obtained from 14 uncomplicated celiac patients before and after 12 months of gluten-free diet, 5 refractory celiac patients, and 12 controls. CD40 was also analyzed by flow cytometry on single cell suspension of mucosal biopsies. Treated celiac biopsies were stimulated with peptic-tryptic digest of gliadin (PT-gliadin) with or without an anti-CD40L-neutralizing antibody. Interferon (IFN)-γ and interleukin (IL)-17 were measured by ELISA (enzyme-linked immunosorbent assay). T-bet, CD40, and CD40L were determined by immunoblotting.

RESULTS

CD40 and CD40L expression was higher in uncomplicated untreated and refractory celiac patients than in controls; the expression returned to normal after gluten-free diet in uncomplicated patients. Flow cytometric analysis confirmed that most CD40(+) cells were dendritic cells. The addition of the anti-CD40L antibody to treated celiac biopsies significantly inhibited the PT-gliadin-induced production of IFN-γ and IL-17, and mucosal T-bet.

CONCLUSIONS

Our results indicate that the CD40-CD40L pathway has a key role in celiac disease. Disruption of CD40-CD40L interaction may offer a therapeutic alternative in refractory celiac disease.

Bifidobacterium lactis attenuates onset of inflammation in a murine model of colitis

AIM

To assess the anti-inflammatory effect of the probiotic Bifidobacterium lactis (B. lactis) in an adoptive transfer model of colitis.

METHODS

Donor and recipient mice received either B. lactis or bacterial culture medium as control (deMan Rogosa Sharpe) in drinking water for one week prior to transfer of a mix of naive and regulatory T cells until sacrifice.

RESULTS

All recipient mice developed signs of colonic inflammation, but a significant reduction of weight loss was observed in B. lactis-fed recipient mice compared to control mice. Moreover, a trend toward a diminution of mucosal thickness and attenuated epithelial damage was revealed. Colonic expression of pro-inflammatory and T cell markers was significantly reduced in B. lactis-fed recipient mice compared to controls. Concomitantly, forkhead box protein 3, a marker of regulatory T cells, was significantly up-regulated by B. lactis.

CONCLUSION

Daily oral administration of B. lactis was able to reduce inflammatory and T cells mediators and to promote regulatory T cells specific markers in a mouse model of colitis.

E-cadherin marks a subset of inflammatory dendritic cells that promote T cell-mediated colitis

Dendritic cells (DCs) play a pivotal role in controlling the balance between tolerance and immunity in the intestine. Gut conditioned CD103⁺ DCs promote regulatory T (Treg) cell responses; however, little is known about DCs that drive inflammation in the intestine. Here, we show that monocyte-derived inflammatory DCs that express E-cadherin, the receptor for CD103, promote intestinal inflammation. E-cadherin⁺ DCs accumulated in the inflamed mesenteric lymph nodes and colon, had high expression of toll-like receptors, and produced colitogenic cytokines, such as IL-6 and IL-23, after activation. Importantly, adoptive transfer of E-cadherin⁺ DCs into T cell-restored immunodeficient hosts increased Th17 cell responses in the intestine and led to exacerbation of colitis. These results identify a monocyte-derived inflammatory DC subset that is associated with the pathogenesis of intestinal inflammation, providing a therapeutic target for the treatment of inflammatory bowel disease.

CD40 and autoimmunity: the dark side of a great activator

CD40 is a tumor necrosis factor receptor superfamily member expressed by immune and non-immune cells. CD40:CD154 interactions mediate T-dependent B cell responses and efficient T cell priming. Thus, CD40 is a likely candidate to play roles in autoimmune diseases in which activated T and B cells cause pathology. Diseases in which CD40 plays a pathogenic role include autoimmune thyroiditis, type 1 diabetes, inflammatory bowel disease, psoriasis, multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus. This review discusses the role of CD40:CD154 interaction in human and mouse autoimmunity, human polymorphisms associated with disease incidence, and disrupting CD40:CD154 interactions as an autoimmune therapy.

New insights into the roles of dendritic cells in intestinal immunity and tolerance

Dendritic cells (DCs) play a critical key role in the initiation of immune responses to pathogens. Paradoxically, they also prevent potentially damaging immune responses being directed against the multitude of harmless antigens, to which the body is exposed daily. These roles are particularly important in the intestine, where only a single layer of epithelial cells provides a barrier against billions of commensal microorganisms, pathogens, and food antigens, over a huge surface area. In the intestine, therefore, DCs are required to perform their dual roles very efficiently to protect the body from the dual threats of invading pathogens and unwanted inflammatory reactions. In this review, we first describe the biology of DCs and their interactions with other cells types, paying particular attention to intestinal DCs. We, then, examine the ways in which this biology may become misdirected, resulting in inflammatory bowel disease. Finally, we discuss how DCs potentiate immune responses against viral, bacterial, parasitic infections, and their importance in the pathogenesis of prion diseases. We, therefore, provide an overview of the complex cellular interactions that affect intestinal DCs and control the balance between immunity and tolerance.

Therapeutic interventions targeting CD40L (CD154) and CD40: the opportunities and challenges

CD40 was originally identified as a receptor on B-cells that delivers contact-dependent T helper signals to B-cells through interaction with CD40 ligand (CD40L, CD154). The pivotal role played by CD40-CD40L interaction is illustrated by the defects in B-lineage cell development and the altered structures of secondary lymphoid tissues in patients and engineered mice deficient in CD40 or CD40L. CD40 signaling also provides critical functions in stimulating antigen presentation, priming of helper and cytotoxic T-cells and a variety of inflammatory reactions. As such, dysregulations in the CD40-CD40L costimulation pathway are prominently featured in human diseases ranging from inflammatory conditions to systemic autoimmunity and tissue-specific autoimmune diseases. Moreover, studies in CD40-expressing cancers have provided convincing evidence that the CD40-CD40L pathway regulates survival of neoplastic cells as well as presentation of tumor-associated antigens to the immune system. Extensive research has been devoted to explore CD40 and CD40L as drug targets. A number of anti-CD40L and anti-CD40 antibodies with diverse biological effects are in clinical development for treatment of cancer and autoimmune diseases. This chapter reviews the role of CD40-CD40L costimulation in disease pathogenesis, the characteristics of therapeutic agents targeting this pathway and status of their clinical development.

Paradoxical effect of reduced costimulation in T cell-mediated colitis

B7-1 and B7-2 play different roles in the pathogenesis of autoimmunity, but this is controversial. We analyzed colitis induced by transfer of CD45RB(high)CD4(+) T cells to RAG(-/-) recipients lacking B7-1 and/or B7-2. Surprisingly, disease was greatly accelerated in RAG(-/-) recipients deficient for either B7-1 or B7-2, especially in the B7-2(-/-) recipients. This accelerated colitis induction correlated with increased T cell division in vivo and production of Th1 cytokines. Although colitis pathogenesis following T cell transfer was inhibited in the absence of CD40L expression, CD40-CD40L interactions were not required in the B7-2(-/-) RAG(-/-) recipients. In vitro priming by APCs lacking either B7-1 or B7-2 caused decreased IL-2 production, which led to decreased CTLA-4 expression, although T cells primed in this way could respond vigorously upon restimulation by producing increased IL-2 and proinflammatory cytokines. Consistent with this mechanism, we demonstrate that blocking IL-2 early after T cell transfer accelerated colitis. Our data therefore outline a mechanism whereby synergistic costimulation by B7-1 and B7-2 molecules during priming is required for optimal IL-2 production. The consequent inhibitory effect of full CTLA-4 expression, induced by IL-2, may slow colitis, even in the absence of regulatory T cells.

CD40-CD40 ligand mediates the recruitment of leukocytes and platelets in the inflamed murine colon

BACKGROUND AND AIMS

Although the CD40-CD40 ligand (CD40L) signaling pathway has been implicated in the pathogenesis of a variety of diseases, including inflammatory bowel disease, the nature of its contribution to intestinal inflammation remains poorly understood. The aim of this study was to determine whether CD40-CD40L contributes to the intestinal inflammatory response, tissue injury, and disease activity elicited by dextran sodium sulphate (DSS) through the modulation of leukocyte and platelet recruitment in the colonic microvasculature.

METHODS

Wild-type (WT), CD40(-/-), and CD40L(-/-) mice were fed DSS drinking water. On day 6, intravital videomicroscopy was performed to monitor leukocyte and platelet recruitment in colonic venules, with measurements obtained for tissue myeloperoxidase and histology. CD40 expression on colonic endothelium was measured using the dual-radiolabeled antibody technique.

RESULTS

A comparison of the responses to DSS-induced colitis in CD40(-/-) and CD40L(-/-) mice to WT mice revealed a significant attenuation of disease activity and histologic damage, as well as profound reductions in the recruitment of adherent leukocytes and platelets in the mutant mice. Similar down-regulation of the blood cell recruitment responses to DSS was noted in WT mice treated with the CD40-CD40L pathway inhibitor Trapidil. CD40 expression in the colonic vasculature was greatly elevated during DSS-induced inflammation in WT mice, but not in CD40(-/-) mice.

CONCLUSIONS

These findings implicate CD40-CD40L in the pathogenesis of DSS-induced intestinal inflammation, and suggest that modulation of leukocyte and platelet recruitment by activated, CD40-positive endothelial cells in colonic venules may represent a major action of this signaling pathway.

Type 1 and 2 T helper cell-mediated colitis

PURPOSE OF REVIEW

Abrogation of mucosal T cell homeostasis by exaggerated not only T helper 1, but also T helper 2 cells is a major problem that leads to intestinal inflammation. In this regard, it is important to understand these different aspects of mucosal inflammation.

RECENT FINDINGS

Both T helper 1 and 2 cells play central roles in the induction of mucosal immune responses including secretory IgA antibody production, which would be the most beneficial aspect for the host defense mechanism. T helper 1- and 2-type responses, however, exhibit other roles in the abrogation of intestinal homeostasis. Although it has been shown that T helper 1-type immune responses are key players in the induction of intestinal inflammation in mice colitis models and also in inflammatory bowel diseases in humans, studies in murine colitis models clearly show that T helper 2-type responses are also involved in the pathophysiology of the intestinal inflammation. Both regulatory type T cells and T helper 17 cells are involved to down- or upregulate aberrant T helper 1 and 2 cell responses.

SUMMARY

Understanding the cellular and molecular mechanisms of crosstalk among T helper 1, 2, 17 and T regulatory 1 cells is central for the prevention or treatment of inflammatory bowel diseases.

The proportion of CD40+ mucosal macrophages is increased in inflammatory bowel disease whereas CD40 ligand (CD154)+ T cells are relatively decreased, suggesting differential modulation of these costimulatory molecules in human gut lamina propria

BACKGROUND

Signal transduction through binding of CD40 on antigen-presenting cells and CD40 ligand (CD154) on T cells appears to be crucial for mutual cellular activation. Antibodies aimed at blocking the CD40-CD154 costimulatory pathway dampen the severity of experimental colitis. To elucidate the microanatomical basis for signaling through this costimulatory pathway in human inflammatory bowel disease, we studied in situ the cellular distribution of these 2 molecules on lamina propria macrophages and T cells, respectively.

METHODS

Colonic specimens from 8 patients with ulcerative colitis and 8 with Crohn's disease, 8 small bowel specimens of Crohn's disease, and histologically normal control samples (6 from colon and 6 from small bowel) were included. Multicolor immunofluorescence in situ staining was performed to determine the percentage of subepithelial macrophages expressing CD40 and that of lamina propria T cells expressing CD154 while avoiding cells in lymphoid aggregates.

RESULTS

The proportion of subepithelial CD40CD68 macrophages was significantly increased in normal colon compared with normal small bowel and showed further elevation in both colon and small bowel afflicted with inflammatory bowel disease. In addition, on a per-CD68-cell basis, CD40 expression was significantly increased in severely inflamed compared with moderately inflamed colonic specimens. Conversely, the proportion of CD154 T cells was similar in colon and small bowel, and interestingly, it was significantly reduced in colonic inflammatory bowel disease.

CONCLUSIONS

Our findings suggested that modulation of CD40 expression by subepithelial macrophages and CD154 by lamina propria T cells is inversely modulated in the human gut.

Regulatory T cells suppress systemic and mucosal immune activation to control intestinal inflammation

The gastrointestinal (GI) tract is the main interface where the body encounters exogenous antigens. It is crucial that the local response here is tightly regulated to avoid an immune reaction against dietary antigens and commensal flora while still mounting an efficient defense against pathogens. Faults in establishing intestinal tolerance can lead to disease, inducing local and often also systemic inflammation. Studies in human as well as in animal models suggest a role for regulatory T cells (Tregs) in maintaining intestinal homeostasis. Transfer of Tregs can not only prevent the development of colitis in animal models but also cure established disease, acting both systemically and at the site of inflammation. In this review, we discuss the major regulatory pathways, including transforming growth factor-beta (TGF-beta), interleukin-10 (IL-10), and cytotoxic T-lymphocyte antigen-4 (CTLA-4), and their role in Treg-mediated control of systemic and mucosal responses. In addition, we give an overview of the known mechanisms of lymphocyte migration to the intestine and discuss how CD103 expression can influence the balance between regulatory and effector T cells. Further understanding of the factors that control the activity of Tregs in different immune compartments may facilitate the design of strategies to target regulation in a tissue-specific way.

Differential Activity of IL-12 and IL-23 in Mucosal and Systemic Innate Immune Pathology

The CD40-CD154 pathway is important in the pathogenesis of inflammatory bowel disease. Here we show that injection of an agonistic CD40 mAb to T and B cell-deficient mice was sufficient to induce a pathogenic systemic and intestinal innate inflammatory response that was functionally dependent on tumor necrosis factor-alpha and interferon-gamma as well as interleukin-12 p40 and interleukin-23 p40 secretion. CD40-induced colitis, but not wasting disease or serum proinflammatory cytokine production, depended on interleukin-23 p19 secretion, whereas interleukin-12 p35 secretion controlled wasting disease and serum cytokine production but not mucosal immunopathology. Intestinal inflammation was associated with IL-23 (p19) mRNA-producing intestinal dendritic cells and IL-17A mRNA within the intestine. Our experiments identified IL-23 as an effector cytokine within the innate intestinal immune system. The differential role of IL-23 in local but not systemic inflammation suggests that it may make a more specific target for the treatment of IBD.

B CELL IMMUNOBIOLOGY IN DISEASE: Evolving Concepts from the Clinic

The pathogenic roles of B cells in autoimmune diseases occur through several mechanistic pathways that include autoantibodies, immune complexes, dendritic and T cell activation, cytokine synthesis, chemokine-mediated functions, and ectopic neolymphogenesis. Each of these pathways participate to different degrees in autoimmune diseases. The use of B cell-targeted and B cell subset-targeted therapies in humans is illuminating the mechanisms at work in a variety of human autoimmune diseases. In this review, we highlight some of these recent findings that provide insights into both murine models of autoimmunity and human autoimmune diseases.

TNF-alpha blockade down-regulates the CD40/CD40L pathway in the mucosal microcirculation: a novel anti-inflammatory mechanism of infliximab in Crohn's disease

The CD40/CD40 ligand (CD40L) pathway is involved in Crohn's disease (CD) pathogenesis. In the patients' circulation, soluble CD40L (sCD40L) levels are elevated and surface CD40L is increased in platelets and T cells, whereas in the intestine CD40 is overexpressed in the microvasculature and CD40L in platelets and T cells. The therapeutic effects of infliximab in CD are attributed to its systemic anti-TNF-alpha action, but because TNF-alpha modulates both CD40 and CD40L, we investigated whether infliximab affects the CD40/CD40L pathway in the intestine. Eighteen CD patients were evaluated before and after infliximab therapy. Plasma sCD40L was measured by ELISA and platelet and peripheral blood T cell (PBT) CD40L expression by flow cytometry. Microvascular CD40 and VCAM-1 expression were assessed in mucosal biopsies by immunohistochemistry and by flow cytometry in human intestinal microvascular endothelial cells (HIMEC). Cell cultures were performed in the presence and absence of infliximab. Infliximab treatment significantly reduced plasma sCD40L levels and eliminated CD40 and VCAM-1 from mucosal microvessels. In vitro infliximab prevented TNF-alpha-induced CD40 and VCAM-1 expression by HIMEC, and reduced PBT, but not platelet, surface CD40L expression and sCD40L release. In addition, infliximab decreased T cell-induced VCAM-1 expression in HIMEC by down-regulating CD40L in T cells and promoting T cells apoptosis. These findings point to a novel mechanism of action of infliximab, i.e., the disruption of CD40/CD40L-dependent cognate interactions between intestinal microvessels and T cells. Thus, in addition to neutralizing TNF-alpha and inducing T cell death, the therapeutic effects of infliximab in CD appear to be also mediated by inhibition of vascular inflammation in the gut.

CD48 controls T-cell and antigen-presenting cell functions in experimental colitis

BACKGROUND & AIMS

The cell-surface receptor CD48 is a lipid-anchored protein expressed on all antigen-presenting cells and T cells. CD2 and 2B4 are known ligands for CD48, which themselves are expressed on the surface of hematopoietic cells. Here we examine the effect of CD48 in the development of chronic experimental colitis and how CD48 affects adaptive and innate immune functions.

METHODS

The role of CD48 in experimental colitis was first assessed by transferring CD4(+)CD45RB(hi) cells isolated from either wild-type or CD48(-/-) mice into either Rag-2(-/-) or CD48(-/-) x Rag-2(-/-) mice. Development of chronic colitis in these adoptively transferred mice was assessed by disease activity index, histology, and production of interferon-gamma in mesenteric lymph nodes. Relevant functions of CD48(-/-)CD4(+) T cells and CD48(-/-) macrophages were examined using in vitro assays. In a second set of experiments, the efficacy of anti-CD48 in prevention or treatment of chronic colitis was determined.

RESULTS

CD48(-/-)CD4(+) cells induced colitis when transferred into Rag-2(-/-) mice, but not when introduced into CD48(-/-) x Rag-2(-/-) recipients. However, both recipient mouse strains developed colitis upon adoptive transfer of wild-type CD4(+) cells. Consistent with a CD4(+) T-cell defect was the observation that in vitro proliferation of CD48(-/-)CD4(+) T cells was impaired upon stimulation with CD48(-/-) macrophages. In vitro evidence for a modest macrophage functional defect was apparent because CD48(-/-) macrophages produced less tumor necrosis factor alpha and interleukin 12 than wild-type cells upon stimulation with lipopolysaccharide. Peritoneal macrophages also showed a defect in clearance of gram-negative bacteria in vitro. Treatment of the CD4(+)CD45RB(hi)-->Rag-2(-/-) mice or the wild-type BM-->tg26 mice with anti-CD48 (HM48-1) ameliorated development of colitis, even after its induction.

CONCLUSIONS

Both CD48-dependent activation of macrophages and CD48-controlled activation of T cells contribute to maintaining the inflammatory response. Consequently, T cell-induced experimental colitis is ameliorated only when CD48 is absent from both T cells and antigen-presenting cells. Because anti-CD48 interferes with these processes, anti-human CD48 antibody treatment may represent a novel therapy for inflammatory bowel disease patients.

Alterations of Mesenchymal and Endothelial Cells in Inflammatory Bowel Diseases

The pathogenesis of complex chronic diseases like inflammatory bowel disease (IBD) can no longer be viewed as a one-way street in which classical immune cells have exclusive control over the initiation, duration and outcome of the disease. There is enough experimental evidence to demonstrate that nonimmune cells, among which are mucosal mesenchymal and endothelial cells, also play a decisive role by interacting with immune cells and establishing a two-way reciprocal exchange of signals and responses that dictate the ultimate outcome of inflammation. Smooth muscle cells and fibroblasts/myofibroblasts display a variety of immune functions and modulate the activity and survival of T-cells. Mucosal microvascular cells, through the expression of adhesion molecules and secretion of chemokines, regulate the quantity and quality of leukocytes transmigrating into the interstitial space. A number of receptor-ligand pairs are expressed by immune and nonimmune cells that control their functional interplay, but the CD40/CD40 ligand system may be the most effective because CD40 is expressed by activated muscle and endothelial cells, while the CD40 ligand is expressed by activated T-cells and platelets. The activation of this system in IBD can lead to the establishment of a continuous cycle of nonimmune cell-dependent, antigen-independent interactions that perpetuates gut inflammation.

Tumor necrosis factor family members and inflammatory bowel disease

Tumor necrosis factor (TNF) is one of the most potent effector cytokines in the pathogenesis of inflammatory bowel disease (IBD). Previous studies strongly implicate the critical involvement of several TNF family members in human IBD. This review focuses on the recent studies of TNF family members in IBD development. In particular, we discuss the findings about LIGHT (homologous to lymphotoxins, inducible expression, competes with herpes simplex virus glycoprotein D for herpes viral entry mediator, a receptor expressed on T lymphocytes) in the pathogenesis of IBD, and the potential mechanisms by which LIGHT induces IBD. Such mechanisms may also apply to other TNF family members.

Regulatory T cells and intestinal homeostasis

Murine models of inflammatory bowel disease (IBD) are useful tools for the study of the pathogenesis and regulation of intestinal inflammation. Colitis can be induced in immune-deficient mice following transfer of populations of T cells or following infection with Helicobacter hepaticus and other intestinal pathogens. In these situations, colitis occurs as a result of the absence of a specialized population of regulatory cells, as transfer of CD4(+)CD25(+) T cells prevents disease. Importantly, from a clinical perspective, CD4(+)CD25(+) T cells can also reverse an established colitis. CD4(+)CD25(+) T cells proliferate both in the secondary lymphoid organs and at the site of inflammation, suggesting that regulation occurs both locally and systemically. CD4(+)CD25(+) T cells are not only capable of regulating other T cells but are also capable of suppressing components of the innate immune system. Control of colitis is dependent on the presence of the immunosuppressive cytokines interleukin-10 and transforming growth factor-beta, although their roles are divergent and complex. Regulatory T cells represent one of the host's mechanisms to prevent immune pathology during chronic immune stimulation. Enhancement of regulatory T-cell activity may be useful to control autoreactive T-cell responses and inhibit harmful inflammatory diseases such as asthma and IBD.

Animal models of intestinal inflammation: ineffective communication between coalition members

The microbiota, epithelial cells, and mucosal immune cells in the intestine comprise an important gastrointestinal coalition. The intestinal microbiota can exert both beneficial as well as deleterious effects on their animal hosts. They interact with the innate defenses provided by epithelial cells through microbial recognition receptors. This communication, under normal conditions, results in a state of controlled inflammation. This article will focus on several animal models of intestinal inflammation, in which spontaneous or induced mutations or other genetic manipulations result in severe alterations in one of the members of the gastrointestinal coalition. These animal models of colitis have shown that alterations in communication between members of this coalition ultimately lead to gastrointestinal disease.

Safety and tolerability of antagonist anti-human CD40 Mab ch5D12 in patients with moderate to severe Crohn's disease

BACKGROUND

The ligation of CD40 by CD154 is a critical step in the interaction between APC and T cells. In animals, antagonizing CD40L-CD40 has been shown to reduce the severity of several autoimmune and inflammatory disorders, including experimental colitis.

AIM

To investigate tolerability and safety of an antagonist chimeric monoclonal anti-human CD40 antibody (ch5D12) for treatment of Crohn's disease.

METHOD

ch5D12 was administrated to 18 patients with moderate to severe Crohn's disease in a single dose, open-label dose-escalation phase I/IIa study.

RESULTS

ch5D12 plasma concentrations increased dose-dependently after infusion. Two patients developed an anti-ch5D12 antibody response. Overall response and remission rates were 72 and 22%, respectively with no evidence for a dose-response effect. Treatment with ch5D12 reduced microscopic disease activity and intensity of the lamina propria cell infiltrate, but did not alter percentages of circulating T and B cells. ch5D12 was well tolerated, although some patients experienced headache, muscle aches, or joint pains, which may have been related to the study drug.

CONCLUSIONS

Antagonizing CD154-CD40 interactions with ch5D12 is a promising therapeutic approach for remission induction in Crohn's disease.

The Critical Role of LIGHT in Promoting Intestinal Inflammation and Crohn’s Disease

Crohn's disease (CD) is a type of inflammatory bowel disease associated with increased Th1 cytokines and unique pathological features. However, its pathogenesis has not been fully understood. Previous studies showed that homologous to lymphotoxin, exhibits inducible expression, competes with herpesvirus glycoprotein D for HVEM on T cells (LIGHT) transgenic (Tg) mice develop autoimmunity including intestinal inflammation with a variable time course. In this study, we establish an experimental model for CD by adoptive transfer of Tg mesenteric lymph node cells into RAG(-/-) mice. The recipients of Tg lymphocytes rapidly develop a disease strikingly similar to the key pathologic features and cytokine characterization observed in CD. We demonstrate that, as a costimulatory molecule, LIGHT preferentially drives Th1 responses. LIGHT-mediated intestinal disease is dependent on both of its identified signaling receptors, lymphotoxin beta receptor and herpes virus entry mediator, because LIGHT Tg mesenteric lymph node cells do not cause intestinal inflammation when transferred into the lymphotoxin beta receptor-deficient mice, and herpes virus entry mediator on donor T cells is required for the full development of disease. Furthermore, we demonstrated that up-regulation of LIGHT is associated with active CD. These data establish a new mouse model resembling CD and suggest that up-regulation of LIGHT may be an important mediator of CD pathogenesis.

In vivo generation of oligoclonal colitic CD4+ T-cell lines expressing a distinct T-cell receptor Vbeta

BACKGROUND & AIMS

Transplantation of wild-type (H-2k) bone marrow into tg epsilon26 mice (BM-->tg epsilon26) induces colitis, characterized by T-helper cell type 1 activation in the lamina propria. Here we determined whether pathogenic T-cell clones could be derived by serial adoptive transfers into healthy tg epsilon26 recipients, starting with the population of CD4+ cells in the mesenteric lymph nodes of BM-->tg epsilon26 mice.

METHODS

CD4+ cells purified from the mesenteric lymph nodes of colitic BM-->tg epsilon26 mice were adoptively transferred into a second group of healthy tg epsilon26 recipients. Mesenteric lymph node CD4+ cells from the second group of mice were then used for consecutive transfers. Lamina propria CD4+ cells isolated from each mouse with colitis were analyzed for their cytokine profile and for their T-cell receptor Vbeta repertoire.

RESULTS

CD4+ T cells maintained a dominant T-helper 1 phenotype after multiple transfers (< or = 8) into recipient tg epsilon26 mice. A single T-cell receptor Vbeta was enriched (as much as 90%) in 8 CD4+ T-cell lines: Vbeta8S3, Vbeta8S1/2, Vbeta10S1, or Vbeta14. Sequence analyses of the T-cell receptor Vbetas showed clonality or the presence of a very restricted number of clones within each line. Adoptive transfers of the oligoclonal lines into either C3H x Rag-/- or severe combined immunodeficiency disease mice (H-2k) also induced colitis, whereas transfers into BALB/c x Rag-/- or severe combined immunodeficiency disease mice (H-2d) did not.

CONCLUSIONS

Colitis-inducing CD4+ T-helper 1 cell clones can be obtained by enrichment through sequential adoptive transfers of CD4+ cells from mesenteric lymph nodes. Distinct dominant T-cell receptor Vbetas in each cell line responded to antigens presented by class II major histocompatibility complex.

Immune regulation in the intestine: a balancing act between effector and regulatory T cell responses

The immune system in the intestine must respond rapidly to invading pathogens without mounting sustained effector cell responses to the indigenous commensal bacteria. Results from this laboratory using the T cell transfer model of colitis suggest that specialized populations of regulatory T cells control the immune response in the intestine. Regulatory T (Tr) cell activity is enriched within the naturally arising CD4(+) CD25(+) Tr subset that has been shown to prevent a number of inflammatory diseases. CD4(+) CD25(+) Tr cells control intestinal inflammation induced by both innate and adaptive immune responses via IL-10- and TGF-beta-dependent mechanisms. Recent results have shown that CD4(+) CD25(+) Tr cells can cure established colitis, suggesting their utility for the treatment of inflammatory bowel disease.

Dominant Role for TL1A/DR3 Pathway in IL-12 plus IL-18-Induced IFN-γ Production by Peripheral Blood and Mucosal CCR9+ T Lymphocytes

The TNF-like cytokine TL1A augments IFN-gamma production by anti-CD3 plus anti-CD28 and IL-12/IL-18-stimulated peripheral blood (PB) T cells. However, only a small subset of PB T cells respond to TL1A stimulation with IFN-gamma production. PB CCR9+ T cells represent a small subset of circulating T cells with mucosal T cell characteristics and a Th1/Tr1 cytokine profile. In the current study, we show that TL1A enhanced IFN-gamma production by TCR- or CD2/CD28-stimulated CCR9(+)CD4+ PB T cells. However, TL1A had the most pronounced effect on augmenting IFN-gamma production by IL-12/IL-18-primed CCR9(+)CD4+ PB T cells. TL1A enhanced both the percentage and the mean fluorescence intensity of IFN-gamma in CCR9(+)CD4+ T cells as assessed by intracellular cytokine staining. IL-12 plus IL-18 up-regulated DR3 expression in CCR9(+)CD4+ T cells but had negligible effect on CCR9(-)CD4+ T cells. CCR9(+)CD4+ T cells isolated from the small intestine showed a 37- to 105-fold enhancement of IFN-gamma production when TL1A was added to the IL-12/IL18 cytokine combination. Cell membrane-expressed TL1A was preferentially expressed in CCR9(+)CD4+ PB T cells, and a blocking anti-TL1A mAb inhibited IFN-gamma production by cytokine-primed CCR9(+)CD4+ T cells by approximately 50%. Our data show that the TL1A/DR3 pathway plays a dominant role in the ultimate level of cytokine-induced IFN-gamma production by CCR9+ mucosal and gut-homing PB T cells and could play an important role in Th1-mediated intestinal diseases, such as Crohn's disease, where increased expression of IL-12, IL-18, TL1A, and DR3 converge in the inflamed intestinal mucosa.

IL-7 exacerbates chronic colitis with expansion of memory IL-7Rhigh CD4+ mucosal T cells in mice

We have previously demonstrated that mucosal CD4(+) T cells expressing high levels of IL-7 receptor (IL-7R(high)) are pathogenic cells responsible for chronic colitis. Here we investigate whether IL-7 is directly involved in the expansion of IL-7R(high) memory CD4(+) mucosal T cells and the exacerbation of colitis. We first showed that CD4(+) lamina propria lymphocytes (LPLs) from wild-type, T cell receptor-alpha-deficient (TCR-alpha(-/-)), and recombinase-activating gene (RAG)-2(-/-)-transferred mice with or without colitis showed phenotypes of memory cells, but only CD4(+) LPLs from colitic mice showed IL-7R(high). In vitro stimulation by IL-7, but not by IL-15 and thymic stromal lymphopoietin, enhanced significant proliferative responses and survival of colitic CD4(+), but not normal CD4(+) LPLs. Importantly, in vivo administration of IL-7 mice accelerated the expansion of IL-7R(high) memory CD4(+) LPLs and thereby exacerbated chronic colitis in RAG-2(-/-) mice transferred with CD4(+) LPLs from colitic TCR-alpha(-/-) mice. Conversely, the administration of anti-IL-7R monoclonal antibody significantly inhibited the development of TCR-alpha(-/-) colitis with decreased expansion of CD4(+) LPLs. Collectively, the present data indicate that IL-7 is essential for the expansion of pathogenic memory CD4(+) T cells under pathological conditions. Therefore, therapeutic approaches targeting the IL-7R pathway may be feasible in the treatment of human inflammatory bowel disease.

CD40 BUT NOT CD154 KNOCKOUT MICE HAVE REDUCED INFLAMMATORY RESPONSE IN POLYMICROBIAL SEPSIS: A POTENTIAL ROLE FOR ESCHERICHIA COLI HEAT SHOCK PROTEIN 70 IN CD40-MEDIATED INFLAMMATION IN VIVO

The CD40-CD154 system controls various aspects of the host inflammatory response in models of cellular and humoral immunity. Recently, we described a role for CD40 in the innate immune response in polymicrobial sepsis. However, recent data suggests that CD40 maybe activated by CD154 or directly via bacterial heat shock protein (HSP) 70. Therefore, we decided to test the mechanism of CD40 activation in murine polymicrobial sepsis. Wild-type (WT), CD40, and CD154 underwent cecal ligation and puncture (CLP). Compared with WT mice, CD40 had improved survival in association with attenuated production of IL-12, TNF-alpha, and IL-6. In contrast, CD154 mice behaved similar to WT mice with regard to mortality and cytokine production. The differential response of CD40 and CD154 mice to CLP was not due to a general attenuated response to inflammatory stimuli, as all three strains had similar survival after LPS administration, and CD40 macrophages had normal production of IL-12 in response to lipopolysaccharide. In contrast, CD40 macrophages had attenuated IL-12 production in response to Escherichia coli HSP70 (DnaK). Furthermore, intraperitoneal administration of DnaK resulted in a 4-fold increase in IL-12 in WT mice, which was absent in CD40 mice. This data demonstrates CD154-independent CD40 activation in polymicrobial sepsis and suggests that bacterial HSP70 is capable of stimulating CD40 in vitro and in vivo.

CD4+CD45RBHi interleukin-4 defective T cells elicit antral gastritis and duodenitis

We have analyzed the gastrointestinal inflammation which develops following adoptive transfer of IL-4 gene knockout (IL-4(-/-)) CD4(+)CD45RB(Hi) (RB(Hi)) T cells to severe combined immunodeficient (SCID) or to T cell-deficient, T cell receptor beta and delta double knockout (TCR(-/-)) mice. Transfer of IL-4(-/-) RB(Hi) T cells induced a similar type of colitis to that seen in SCID or TCR(-/-) recipients of wild-type (wt) RB(Hi) T cells as reported previously. Interestingly, transfer of both wt and IL-4(-/-) RB(Hi) T cells to TCR(-/-) but not to SCID mice induced inflammation in the gastric mucosa. Notably, TCR(-/-) recipients of IL-4(-/-) RB(Hi) T cells developed a more severe gastritis with erosion, apoptosis of the antral epithelium, and massive infiltration of macrophages. This gastritis was partially dependent on the indigenous microflora. Recipients of both wt and IL-4(-/-) RB(Hi) T cells developed duodenitis with multinuclear giant cells, expansion of mucosal macrophages, and dendritic cells. Full B cell responses were reconstituted in TCR(-/-) recipients of RB(Hi) T cells; however, anti-gastric autoantibodies were not detected. We have now developed and characterized a novel model of chronic gastroduodenitis in mice, which will help in our understanding of the mechanisms involved in chronic inflammation in the upper gastrointestinal tract of humans.

Association between enhanced soluble CD40 ligand and prothrombotic state in inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease is associated with an increased incidence of thromboembolic complications. The aim of this study was to investigate the role of the soluble CD40 ligand (sCD40L), which displays prothrombotic properties, in patients with ulcerative colitis (UC) and Crohn's disease (CD) in comparison with inflammatory and healthy controls.

METHODS

Plasma levels of sCD40L, prothrombin fragment 1+2 (F1+2), thrombin-antithrombin (TAT) complex and soluble P-selectin were measured in 104 inflammatory bowel disease patients (54 ulcerative colitis and 50 Crohn's disease), in 18 cases with other causes of intestinal inflammation and in 80 healthy controls using commercially available enzyme-linked immunosorbent assays. Plasma levels of sCD40L were correlated with disease activity, type, localization and treatment as well as with the measured thrombophilic parameters.

RESULTS

CD patients had significantly higher sCD40L levels than both groups of controls (CD vs HC P < 0.001; CD vs non-IBD P < 0.05). UC patients had higher but not significantly different sCD40L levels compared with the controls. Both UC and CD patients with active disease had significantly higher sCD40L levels in comparison with patients with inactive disease. Plasma levels of sCD40L were correlated with platelet count (r = 0.27, P = 0.001). They also showed a correlation with prothrombin F1+2 (r = 0.16, r = 0.03) and TAT (r = 0.15, r = 0.04) as well as with P-selectin (r = 0.19, P = 0.01).

CONCLUSIONS

The increased sCD40L plasma levels may represent, at least in some degree, a molecular link between inflammatory bowel disease and the procoagualant state.

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.