Heat shock factor 1 drives regulatory T-cell induction to limit murine intestinal inflammation.

The heat shock response is a critical component of the inflammatory cascade that prevents misfolding of new proteins and regulates immune responses. Activation of clusters of differentiation (CD)4+ T cells causes an upregulation of heat shock transcription factor, heat shock factor 1 (HSF1). We hypothesized that HSF1 promotes a pro-regulatory phenotype during inflammation. To validate this hypothesis, we interrogated cell-specific HSF1 knockout mice and HSF1 transgenic mice using in vitro and in vivo techniques. We determined that while HSF1 expression was induced by anti-CD3 stimulation alone, the combination of anti-CD3 and transforming growth factor ß, a vital cytokine for regulatory T cell (Treg) development, resulted in increased activating phosphorylation of HSF1, leading to increased nuclear translocation and binding to heat shock response elements. Using chromatin immunoprecipitation (ChIP), we demonstrate the direct binding of HSF1 to foxp3 in isolated murine CD4+ T cells, which in turn coincided with induction of FoxP3 expression. We defined that conditional knockout of HSF1 decreased development and function of Tregs and overexpression of HSF1 led to increased expression of FoxP3 along with enhanced Treg suppressive function. Adoptive transfer of CD45RBHigh CD4 colitogenic T cells along with HSF1 transgenic CD25+ Tregs prevented intestinal inflammation when wild-type Tregs did not. Finally, overexpression of HSF1 provided enhanced barrier function and protection from murine ileitis. This study demonstrates that HSF1 promotes Treg development and function and may represent both a crucial step in the development of induced regulatory T cells and an exciting target for the treatment of inflammatory diseases with a regulatory T-cell component. SIGNIFICANCE STATEMENT: The heat shock response (HSR) is a canonical stress response triggered by a multitude of stressors, including inflammation. Evidence supports the role of the HSR in regulating inflammation, yet there is a paucity of data on its influence in T cells specifically. Gut homeostasis reflects a balance between regulatory clusters of differentiation (CD)4+ T cells and pro-inflammatory T-helper (Th)17 cells. We show that upon activation within T cells, heat shock factor 1 (HSF1) translocates to the nucleus, and stimulates Treg-specific gene expression. HSF1 deficiency hinders Treg development and function and conversely, HSF1 overexpression enhances Treg development and function. While this work, focuses on HSF1 as a novel therapeutic target for intestinal inflammation, the findings have significance for a broad range of inflammatory conditions.

Muc5ac Expression Protects the Colonic Barrier in Experimental Colitis.

BACKGROUND: The mucus gel layer (MGL) lining the colon is integral to exclusion of bacteria and maintaining intestinal homeostasis in health and disease. Some MGL defects allowing bacteria to directly contact the colonic surface are commonly observed in ulcerative colitis (UC). The major macromolecular component of the colonic MGL is the secreted gel-forming mucin MUC2, whose expression is essential for homeostasis in health. In UC, another gel-forming mucin, MUC5AC, is induced. In mice, Muc5ac is protective during intestinal helminth infection. Here we tested the expression and functional role of MUC5AC/Muc5ac in UC biopsies and murine colitis. METHODS: We measured MUC5AC/Muc5ac expression in UC biopsies and in dextran sulfate sodium (DSS) colitis. We performed DSS colitis in mice deficient in Muc5ac (Muc5ac-/-) to model the potential functional role of Muc5ac in colitis. To assess MGL integrity, we quantified bacterial-epithelial interaction and translocation to mesenteric lymph nodes. Antibiotic treatment and 16S rRNA gene sequencing were performed to directly investigate the role of bacteria in murine colitis. RESULTS: Colonic MUC5AC/Muc5ac mRNA expression increased significantly in active UC and murine colitis. Muc5ac-/- mice experienced worsened injury and inflammation in DSS colitis compared with control mice. This result was associated with increased bacterial-epithelial contact and translocation to the mesenteric lymph nodes. However, no change in microbial abundance or community composition was noted. Antibiotic treatment normalized colitis severity in Muc5ac-/- mice to that of antibiotic-treated control mice. CONCLUSIONS: MUC5AC/Muc5ac induction in the acutely inflamed colon controls injury by reducing bacterial breach of the MGL.

miR-106a deficiency attenuates inflammation in murine IBD models.

Pro-inflammatory cytokine TNFα antagonizes regulatory T cell (Treg) suppressive function with a measurable reduction of IL-10 protein secretion. Tregs are critical to suppress excessive immune activation, particularly within the intestine where high antigenic loads elicit chronic subclinical immune activation. Employing a TNFα-driven murine inflammatory bowel disease (IBD) model (TNFΔARE/+), which mirrors the Treg expansion and transmural ileitis seen in Crohn's disease, we demonstrate that the TNFα-mediated loss of Treg suppressive function coincides with induction of a specific miRNA, miR-106a in both humans and mice, via NFκB promoter binding to suppress post-transcriptional regulation of IL-10 release. Elevation of miR-106a and impaired Treg function in this model recapitulate clinical data from IBD patients. MiR-106a deficiency promotes Treg induction, suppressive function and IL-10 production in vitro. MiR-106a knockout attenuated chronic murine ileitis, whereas T cell restricted deficiency of miR-106a attenuated adoptive transfer colitis. In both models, attenuated inflammation coincided with suppression of both Th1 and Th17 cell subset expansion within the intestinal lamina propria. Collectively, our data demonstrate impaired Treg suppressive function in a murine IBD model consistent with human disease and support the potential for inhibition of miR-106a as a future therapeutic approach to treat chronic inflammatory conditions including IBD.

Coordination of ENT2-dependent adenosine transport and signaling dampens mucosal inflammation.

Intestinal epithelial barrier repair is vital for remission in inflammatory bowel disease (IBD). Extracellular adenosine signaling has been implicated in promoting restoration of epithelial barrier function. Currently, no clinically approved agents target this pathway. Adenosine signaling is terminated by uptake from the extracellular space via equilibrative nucleoside transporters (ENTs). We hypothesized that ENT inhibition could dampen intestinal inflammation. Initial studies demonstrated transcriptional repression of ENT1 and ENT2 in IBD biopsies or in murine IBD models. Subsequent studies in mice with global Ent1 or Ent2 deletion revealed selective protection of Ent2-/- mice. Elevated intestinal adenosine levels in conjunction with abolished protection following pharmacologic blockade of A2B adenosine receptors implicate adenosine signaling as the mechanism of gut protection in Ent2-/- mice. Additional studies in mice with tissue-specific deletion of Ent2 uncovered epithelial Ent2 as the target. Moreover, intestinal protection provided by a selective Ent2 inhibitor was abolished in mice with epithelium-specific deletion of Ent2 or the A2B adenosine receptor. Taken together, these findings indicate that increased mucosal A2B signaling following repression or deletion of epithelial Ent2 coordinates the resolution of intestinal inflammation. This study suggests the presence of a targetable purinergic network within the intestinal epithelium designed to limit tissue inflammation.

C/EBPß Deletion Promotes Expansion of Poorly Functional Intestinal Regulatory T Cells.

BACKGROUND AND AIMS: Inflammatory Bowel Diseases [IBDs] are chronic intestinal inflammatory conditions in part mediated by CD4+ T cells. Anti-inflammatory Foxp3+ regulatory T cells [Tregs] maintain immune homeostasis and protect against IBD development via multiple mechanisms, including cytokine secretion and cell-cell interaction. CCAAT enhancer binding protein-beta [C/EBPß] is a stress-responsive transcription factor linked with IBD susceptibility. Whole-body C/EBPß deficiency induces CD4+ T cell-predominant hyperproliferation, and we hypothesize that this may be due to impaired Treg function. METHODS: We used the C/EBPß-/- mice in the CD45RBHigh adoptive transfer model, to assess C/EBPß-/- CD4+ T cells for their colitiogenic potential, and C/EBPß-/- CD4+ Foxp3+ Tregs for their ability to inhibit colitis. We assessed Tregs from the C/EBPß-/- mice for expression of Treg functional genes and proteins. RESULTS: Naïve C/EBPß-/- CD4+ T cells are more colitogenic in vivo. The exacerbated colitis does not appear to reflect impaired Treg development, however, as C/EBPß-/- mice displayed more, rather than fewer intestinal CD4+Foxp3+ Tregs in vivo. Instead, this reflects impaired Treg function as seen by the reduced capacity to suppress T cell proliferation in vitro, along with decreased secretion of the anti-inflammatory cytokine IL-10. These findings were corroborated in vivo by additional adoptive co-transfer studies in which wildtype Tregs prevented colitis but C/EBPß-/- Tregs did not. CONCLUSION: C/EBPß deficiency impairs Treg function and potentiates T cell-mediated colitis. A clearer understanding of the function of this transcription factor may provide a novel therapeutic strategy for IBD.

Cannabinoid Receptor-2 Ameliorates Inflammation in Murine Model of Crohn's Disease.

BACKGROUND AND AIMS: Cannabinoid receptor stimulation may have positive symptomatic effects on inflammatory bowel disease [IBD] patients through analgesic and anti-inflammatory effects. The cannabinoid 2 receptor [CB2R] is expressed primarily on immune cells, including CD4+ T cells, and is induced by active inflammation in both humans and mice. We therefore investigated the effect of targeting CB2R in a preclinical IBD model. METHODS: Employing a chronic ileitis model [TNFΔARE/+ mice], we assessed expression of the CB2R receptor in ileal tissue and on CD4+ T cells and evaluated the effect of stimulation with CB2R-selective ligand GP-1a both in vitro and in vivo. Additionally, we compared cannabinoid receptor expression in the ilea and colons of healthy human controls with that of Crohn's disease patients. RESULTS: Ileal expression of CB2R and the endocannabinoid anandamide [AEA] was increased in actively inflamed TNF∆ARE/+ mice compared with controls. CB2R mRNA was preferentially induced on regulatory T cells [Tregs] compared with T effector cells, approximately 2.4-fold in wild-type [WT] and 11-fold in TNF∆ARE/+ mice. Furthermore, GP-1a enhanced Treg suppressive function with a concomitant increase in IL-10 secretion. GP-1a attenuated murine ileitis, as demonstrated by improved histological scoring and decreased inflammatory cytokine expression. Lastly, CB2R is downregulated in both chronically inflamed TNF∆ARE/+ mice and in IBD patients. CONCLUSIONS: In summary, the endocannabinoid system is induced in murine ileitis but is downregulated in chronic murine and human intestinal inflammation, and CB2R activation attenuates murine ileitis, establishing an anti-inflammatory role of the endocannabinoid system.

VEN-120, a Recombinant Human Lactoferrin, Promotes a Regulatory T Cell [Treg] Phenotype and Drives Resolution of Inflammation in Distinct Murine Models of Inflammatory Bowel Disease.

BACKGROUND AND AIMS: Inflammatory bowel disease [IBD] is characterised by a disruption of immune homeostasis, which is tightly regulated to protect against harmful pathogens yet not react to commensal antigens. Animal studies indicate that regulatory T cells [Treg] modulate the immune response to prevent IBD development. Lactoferrin [LF] is an endogenous anti-inflammatory pleiotropic protein secreted at high concentrations in colostrum and at mucosal sites. However, the effect of LF on specific T lymphocyte populations has not been studied. Here, we identify a novel mechanism by which a recombinant human LF, VEN-120, regulates T cell populations in health and disease. METHODS: Two murine models of intestinal inflammation, the dextran sodium sulphate colitis model and the TNFΔARE/+ model of ileitis, were used to study the anti-inflammatory and T cell modulating ability of VEN-120. Flow cytometry was used to evaluate T cell populations within the lamina propria and mesenteric lymph nodes, and to evaluate the effect of VEN-120 on CD4+ T cells in vitro. RESULTS: VEN-120 reduced inflammation in both models of IBD, accompanied by increased Tregs in the intestinal lamina propria. Treatment of CD4+ T cells in vitro resulted in an upregulation of Treg genes and skewing towards a Treg population. This in vitro T cell skewing translated to an increase of Treg homing to the intestinal lamina propria and associated lymph tissue in healthy mice. CONCLUSIONS: These data provide a novel immunological mechanism by which VEN-120 modulates T cells to restrict inflammatory T cell-driven disease.

Manipulation of the Endocannabinoid System in Colitis: A Comprehensive Review.

BACKGROUND: Inflammatory bowel disease (IBD) is a lifelong disease of the gastrointestinal tract whose annual incidence and prevalence is on the rise. Current immunosuppressive therapies available for treatment of IBD offer limited benefits and lose effectiveness, exposing a significant need for the development of novel therapies. In the clinical setting, cannabis has been shown to provide patients with IBD symptomatic relief, although the underlying mechanisms of their anti-inflammatory effects remain unclear. METHODS: This review reflects our current understanding of how targeting the endocannabinoid system, including cannabinoid receptors 1 and 2, endogenous cannabinoids anandamide and 2-arachidonoylglycerol, atypical cannabinoids, and degrading enzymes including fatty acid amide hydrolase and monoacylglycerol lipase, impacts murine colitis. In addition, the impact of cannabinoids on the human immune system is summarized. RESULTS: Cannabinoid receptors 1 and 2, endogenous cannabinoids, and atypical cannabinoids are upregulated in inflammation, and their presence and stimulation attenuate murine colitis, whereas cannabinoid receptor antagonism and cannabinoid receptor deficient models reverse these anti-inflammatory effects. In addition, inhibition of endocannabinoid degradation through monoacylglycerol lipase and fatty acid amide hydrolase blockade can also attenuate colitis development, and is closely linked to cannabinoid receptor expression. CONCLUSIONS: Although manipulation of the endocannabinoid system in murine colitis has proven to be largely beneficial in attenuating inflammation, there is a paucity of human study data. Further research is essential to clearly elucidate the specific mechanisms driving this anti-inflammatory effect for the development of therapeutics to target inflammatory disease such as IBD.

Diverse Intestinal Bacteria Contain Putative Zwitterionic Capsular Polysaccharides with Anti-inflammatory Properties.

Zwitterionic capsular polysaccharides (ZPSs) are bacterial products that modulate T cells, including inducing anti-inflammatory IL-10-secreting T regulatory cells (Tregs). However, only a few diverse bacteria are known to modulate the host immune system via ZPS. We present a genomic screen for bacteria encoding ZPS molecules. We identify diverse host-associated bacteria, including commensals and pathogens with known anti-inflammatory properties, with the capacity to produce ZPSs. Human mononuclear cells stimulated with lysates from putative ZPS-producing bacteria induce significantly greater IL-10 production and higher proportions of Tregs than lysates from non-ZPS-encoding relatives or a commensal strain of Bacteroides cellulosilyticus in which a putative ZPS biosynthetic operon was genetically disrupted. Similarly, wild-type B. cellulosilyticus DSM 14838, but not a close relative lacking a putative ZPS, attenuated experimental colitis in mice. Collectively, this screen identifies bacterial strains that may use ZPSs to interact with the host as well as those with potential probiotic properties.

γδ T cells protect against LPS-induced lung injury.

γδ T lymphocytes are a unique T cell population with important anti-inflammatory capabilities. Their role in acute lung injury, however, is poorly understood but may provide significant insight into lung-protective mechanisms occurring after injury. In a murine model of lung injury, wild-type C57BL/6 and TCRδ(-/-) mice were exposed to Escherichia coli LPS, followed by analysis of γδ T cell and macrophage subsets. In the absence of γδ T cells, TCRδ(-/-) mice developed increased inflammation and alveolar-capillary leak compared with wild-type C57BL/6 mice after LPS exposure that correlated with expansion of distinct macrophage populations. Classically activated M1 macrophages were increased in the lung of TCRδ(-/-) mice at d 1, 4, and 7 after LPS exposure that peaked at d 4 and persisted at d 7 compared with wild-type animals. In response to LPS, Vγ1 and Vγ7 γδ T cells were expanded in the lung and expressed IL-4. Coculture experiments showed decreased expression of TNF-α by resident alveolar macrophages in the presence of γδ T cells that was reversed in the presence of an anti-IL-4-blocking antibody. Treatment of mice with rIL4 resulted in reduced numbers of M1 macrophages, inflammation, and alveolar-capillary leak. Therefore, one mechanism by which Vγ1 and Vγ7 γδ T cells protect against LPS-induced lung injury is through IL-4 expression, which decreases TNF-α production by resident alveolar macrophages, thus reducing accumulation of M1 macrophages, inflammation, and alveolar-capillary leak.

Prospects for Therapeutic Targeting of MicroRNAs in Human Immunological Diseases.

MicroRNAs (miRNAs) are endogenous oligoribonucleotides with exciting therapeutic potential. Early studies established a clear role for miRNAs in leukocyte biology. The first miRNA-based therapy, miravirsen, is now in phase 2 clinical trials, making the reality of these therapies undeniable. The capacity for miRNAs to fine-tune inflammatory signaling make them attractive treatment targets for immunological diseases. Nonetheless, the degree of redundancy among miRNAs, coupled with the promiscuity of miRNA binding sites in the transcriptome, require consideration when designing miRNA-directed interventions. Altered miRNA expression occurs across a range of inflammatory conditions, including inflammatory bowel disease, arthritis, and diabetes. However, very few studies successfully treated murine models of immunological diseases with miRNA-based approaches. While discussing recent studies targeting miRNAs to treat immunological conditions, we also reflect on the risks of miRNA targeting and showcase some newer delivery systems that may improve the pharmacological profile of this class of therapeutics.

Chemokine receptor CCR7 regulates the intestinal TH1/TH17/Treg balance during Crohn's-like murine ileitis.

The regulation of T cell and DC retention and lymphatic egress within and from the intestine is critical for intestinal immunosurveillance; however, the cellular processes that orchestrate this balance during IBD remain poorly defined. With the use of a mouse model of TNF-driven Crohn's-like ileitis (TNF(Δ) (ARE)), we examined the role of CCR7 in the control of intestinal T cell and DC retention/egress during experimental CD. We observed that the frequency of CCR7-expressing TH1/TH17 effector lymphocytes increased during active disease in TNF(Δ) (ARE) mice and that ΔARE/CCR7(-/-) mice developed exacerbated ileitis and multiorgan inflammation, with a marked polarization and ileal retention of TH1 effector CD4(+) T cells. Furthermore, adoptive transfer of ΔARE/CCR7(-/-) effector CD4(+) into lymphopenic hosts resulted in ileo-colitis, whereas those transferred with ΔARE/CCR7(+/+) CD4(+) T cells developed ileitis. ΔARE/CCR7(-/-) mice had an acellular draining MLN, decreased CD103(+) DC, and decreased expression of RALDH enzymes and of CD4(+)CD25(+)FoxP3(+) Tregs. Lastly, a mAb against CCR7 exacerbated ileitis in TNF(Δ) (ARE) mice, phenocopying the effects of congenital CCR7 deficiency. Our data underscore a critical role for the lymphoid chemokine receptor CCR7 in orchestrating immune cell traffic and TH1 versus TH17 bias during chronic murine ileitis.

Targeted inhibition of heat shock protein 90 suppresses tumor necrosis factor-α and ameliorates murine intestinal inflammation.

Inflammatory bowel diseases are chronic intestinal inflammatory diseases thought to reflect a dysregulated immune response. Although antibody-based inhibition of tumor necrosis factor-α (TNF-α) has provided relief to many inflammatory bowel diseases patients, these therapies are either ineffective in a patient subset or lose their efficacy over time, leaving an unmet need for alternatives. Given the critical role of the heat shock response in regulating inflammation, this study proposed to define the impact of selective inhibition of heat shock protein 90 (HSP90) on intestinal inflammation. Using multiple preclinical mouse models of inflammatory bowel diseases, we demonstrate a potent anti-inflammatory effect of selective inhibition of the HSP90 C-terminal ATPase using the compound novobiocin. Novobiocin-attenuated dextran sulfate sodium-induced colitis and CD45RB adoptive-transfer colitis through the suppression of inflammatory cytokine secretion, including TNF-α. In vitro assays demonstrate that CD4 T cells treated with novobiocin produced significantly less TNF-α measured by intracellular cytokine staining and by enzyme-linked immunosorbent assay. This corresponded to significantly decreased nuclear p65 translocation by Western blot and a decrease in nuclear factor-κB luciferase activity in Jurkat T cells. Finally, to verify the anti-TNF action of novobiocin, 20-week-old TNFΔ mice were treated for 2 weeks with subcutaneous administration of novobiocin. This model has high levels of circulating TNF-α and exhibits spontaneous transmural segmental ileitis. Novobiocin treatment significantly reduced inflammatory cell infiltrate in the ileal lamina propria. HSP90 inhibition with novobiocin offers a novel method of inflammatory cytokine suppression without potential for the development of tolerance that limits current antibody-based methods.

IFN-γ-mediated induction of an apical IL-10 receptor on polarized intestinal epithelia.

Cytokines secreted at sites of inflammation impact the onset, progression, and resolution of inflammation. In this article, we investigated potential proresolving mechanisms of IFN-γ in models of inflammatory bowel disease. Guided by initial microarray analysis, in vitro studies revealed that IFN-γ selectively induced the expression of IL-10R1 on intestinal epithelia. Further analysis revealed that IL-10R1 was expressed predominantly on the apical membrane of polarized epithelial cells. Receptor activation functionally induced canonical IL-10 target gene expression in epithelia, concomitant with enhanced barrier restitution. Furthermore, knockdown of IL-10R1 in intestinal epithelial cells results in impaired barrier function in vitro. Colonic tissue isolated from murine colitis revealed that levels of IL-10R1 and suppressor of cytokine signaling 3 were increased in the epithelium and coincided with increased tissue IFN-γ and IL-10 cytokines. In parallel, studies showed that treatment of mice with rIFN-γ was sufficient to drive expression of IL-10R1 in the colonic epithelium. Studies of dextran sodium sulfate colitis in intestinal epithelial-specific IL-10R1-null mice revealed a remarkable increase in disease susceptibility associated with increased intestinal permeability. Together, these results provide novel insight into the crucial and underappreciated role of epithelial IL-10 signaling in the maintenance and restitution of epithelial barrier and of the temporal regulation of these pathways by IFN-γ.

Alpha-1-antitrypsin therapy ameliorates acute colitis and chronic murine ileitis.

BACKGROUND: Fecal alpha-1-antitrypsin (AAT) clearance has been a marker of clinical disease severity in inflammatory bowel diseases (IBDs) for many years. Although AAT deficiency is more often associated with lung and liver pathologies, AAT-deficient patients with concomitant IBD have been shown to develop more aggressive disease and rapid progression to surgery. Although recent studies have highlighted the pleiotropic anti-inflammatory functions of AAT, including reducing proinflammatory cytokine production and suppressing immune cell activation, its potential therapeutic role in IBD has not been described. METHODS: The therapeutic potential of human AAT administration was assessed in murine models of IBD including new-onset and established chemically induced colitis and spontaneous chronic murine ileitis. Histological assessment of inflammation, cytokine secretion profiling, and flow cytometric evaluation of inflammatory infiltrate were performed in each model. The effect of AAT on intestinal barrier function was also examined both in vitro and in vivo. RESULTS: AAT attenuated inflammation in small and large intestinal IBD models through reduced secretion of proinflammatory cytokines, inflammatory cell infiltration, and reduced tissue injury. AAT also increased intestinal restitution after chemically induced colitis. AAT significantly decreased intestinal permeability in vitro and in vivo as part of a protective mechanism for both acute and chronic models of IBD. CONCLUSIONS: Our findings describe a beneficial role for AAT in IBD models through suppression of cytokine production and enhanced intestinal barrier function. This raises the possibility that AAT supplementation, which has a long history of proven safety, may have a therapeutic effect in human IBD.

Ectopic lymphoid tissue alters the chemokine gradient, increases lymphocyte retention and exacerbates murine ileitis.

BACKGROUND: The earliest endoscopically-evident lesion in Crohn's disease is the aphthous ulcer, which develops over ectopic lymphoid tissues (ie, inducible lymphoid follicles (ILF), tertiary lymphoid tissue (TLT)) in the chronically inflamed intestine. ILF/TLT are induced within effector sites by homeostatic lymphoid chemokines, but their role in the development of intestinal ILF/TLT and in the pathogenesis of Crohn's disease is poorly understood. DESIGN: Using a mouse model of Crohn's-like ileitis (TNFARE) which develops florid induction of ILF/TLT within its terminal ileum, the contribution of the CCR7/CCL19/CCL21 chemokine axis during the development of TLT and its role in disease pathogenesis were assessed. RESULTS: Both CCL19 and CCL21 were increased within the inflamed ileum of TNFARE mice, which resulted in CCR7 internalisation and impaired T cell chemotaxis. ILF/TLT were a major source of CCL19 and CCL21 and increased local synthesis, augmented recruitment/retention of effector, naïve and central memory T cell subsets within the inflamed ileum. Immunoblockade of CCR7 resulted in further effector T cell retention and exacerbation of ileitis. CONCLUSIONS: Induction of ILF/TLT in the chronically inflamed intestine alters the homeostatic CCL19-CCL21 lymphoid-chemokine gradient and increases recruitment/retention of effector CCR7+ T cell subsets within the terminal ileum, contributing to the perpetuation of chronic inflammation. Thus, blockade of CCR7 or its ligands might result in deleterious consequences for subjects with chronic inflammatory diseases.