Interleukin-15 and its soluble receptor mediate the response to infliximab in patients with Crohn's disease

Innate Immunity Activation in Newly Diagnosed Ileocolonic Crohn's Disease: A Cohort Study

BACKGROUND

Recent studies showed that early surgery for Crohn's disease leads to a lower recurrence rate. However, the underlying mechanism is unknown.

OBJECTIVE

The study aims to analyze the innate immunity microenvironment in ileal mucosa according to the duration of Crohn's disease.

DESIGN

A prospective cohort study.

SETTINGS

Tertiary referral center for IBD surgery.

PATIENTS

A total of 88 consecutive patients with Crohn's disease undergoing ileocolonic resection were prospectively enrolled. Mucosal samples were obtained from both healthy and inflamed ileum. Data from a public data set were analyzed as an external validation cohort.

MAIN OUTCOME MEASURES

Neutrophil infiltration was evaluated by histological asessment and macrophage subpopulation was assessed by immunohistochemistry. Expressions of TLR2 , TLR4 , TLR5 , DEFB1 , DEFB4A , DEFB103 , DEFA5 , and DEFA6 were quantified by real-time quantitative polymerase chain reaction. Concentrations of BDNF, CCL-11, ICAM-1, IL-1A, IL-1β, IL-1RN, IL-12p40, IL-12p70, IL-15, IL-17A, IL-23A, MMP-3, CCL-3, KITLG, and VEGFA were determined with an immunometric assay.

RESULTS

Neutrophil infiltration is inversely correlated with disease duration. DEFB4A mRNA expression tended to be higher in late-stage Crohn's disease ( p = 0.07). A higher number of macrophages expressed CD163 at low intensity in late-stage Crohn's disease ( p = 0.04). The concentration of IL-15 ( p = 0.02) and IL-23A ( p = 0.05) was higher in healthy ileal mucosa of early-stage patients. In the external cohort, expressions of DEFB1 ( p = 0.03), DEFB4A ( p = 0.01), IL-2 ( p = 0.04), and IL-3 ( p = 0.03) increased in patients with late-stage Crohn's disease.

LIMITATIONS

A relatively small number of patients, especially in the newly diagnosed group.

CONCLUSIONS

In newly diagnosed Crohn's disease, high levels of IL-15 and IL-23 in healthy mucosa suggest that innate immunity is the starter of acute inflammation. Moreover, M2 macrophages increase in the healthy mucosa of patients with late-stage Crohn's disease, suggesting that reparative and profibrotic processes are predominant in the long term, and in this phase, anti-inflammatory therapy may be less efficient. See Video Abstract .

ACTIVACIN DE LA INMUNIDAD INNATA EN LA RECIENTEMENTE DIAGNOSTICADA ENFERMEDAD DE CROHN ILEOCLICA UN ESTUDIO DE COHORTE

ANTECEDENTES:Estudios recientes demostraron que la cirugía temprana para la enfermedad de Crohn (EC) conduce a una menor tasa de recurrencia. Sin embargo, se desconoce el mecanismo subyacente.OBJETIVO:El estudio tiene como objetivo analizar el microambiente de la inmunidad innata en la mucosa ileal según la duración de la EC.DISEÑO:Un estudio de cohorte prospectivo.AJUSTES:Centro terciario de referencia para cirugía de EII.PACIENTES:Fueron registrados de manera prospectiva y consecutiva 88 pacientes con EC sometidos a resección ileocolónica. Se obtuvieron muestras de mucosa ileal, tanto del íleon sano como del íleon inflamado. Los datos se analizaron como una cohorte de validación externa.PRINCIPALES MEDIDAS DE RESULTADO:Fueron evaluados la infiltración de neutrófilos por histología y la subpoblación de macrófagos por inmunohistoquímica. La expresión de TLR2, TLR4, TLR5, DEFB1, DEFB4A, DEFB103, DEFA5 y DEFA6 fueron cuantificados mediante qPCR en tiempo real. Las concentraciones de BDNF, CCL-11, ICAM-1, IL-1A, IL-1B, IL-1RN, IL-12 p40, IL-12 p70, IL-15, IL-17A, IL-23A, MMP-3, CCL-3, KITLG, VEGFA se determinaron con ensayo inmunométrico.RESULTADOS:La infiltración de neutrófilos se correlaciona inversamente con la duración de la enfermedad. La expresión del ARNm de DEFB4A mostro una tendencia a ser mayor en la EC en etapa tardía ( p = 0,07). Un mayor número de macrófagos expresaron CD163 a baja intensidad en la etapa tardía ( p = 0,04). La concentración de IL15 ( p = 0,02) e IL23A ( p = 0,05) fue mayor en la mucosa ileal sana de pacientes en estadio temprano. En la cohorte externa, la expresión de DEFB1 ( p = 0,03) y DEFB4A ( p = 0,01), IL2 ( p = 0,04) e IL3 ( p = 0,03) aumentó en pacientes en etapa tardía.LIMITACIONES:Un número relativamente pequeño de pacientes, especialmente en el grupo recién diagnosticado.CONCLUSIONES:En la EC recién diagnosticada, los altos niveles de IL-15 e IL-23 en la mucosa sana sugieren que la inmunidad innata es el promotor de la inflamación aguda. Además, los macrófagos M2 aumentan en la mucosa sana de pacientes con EC en etapa tardía, lo que sugiere que los procesos reparadores y profibróticos son predominantes a largo plazo y en esta fase, la terapia antiinflamatoria puede ser menos eficiente. (Traducción-Dr. Osvaldo Gauto ).

Discerning Endoscopic Severity of Inflammatory Bowel Disease by Scoping the Peripheral Blood Transcriptome

Background and Aims

Ulcerative colitis (UC) and Crohn's disease (CD) are chronic inflammatory bowel diseases (IBDs) with an incompletely understood etiology and pathogenesis. Identification of suitable drug targets and assessment of disease severity are crucial for optimal management.

Methods

Using RNA sequencing, we investigated differential gene expression in peripheral blood samples from IBD patients and non-inflamed controls, analyzed pathway enrichment, and identified genes whose expression correlated with endoscopic disease severity.

Results

Neutrophil degranulation emerged as the most significant pathway across all IBD sample types. Signaling by interleukins was prominent in patients with active intestinal inflammation but also enriched in CD and UC patients without intestinal inflammation. Nevertheless, genes correlated to endoscopic disease severity implicated the primary cilium in CD patients and translation and focal adhesion in UC patients. Moreover, several of these genes were located in genome-wide associated loci linked to IBD, cholesterol levels, blood cell counts, and levels of markers assessing liver and kidney function. These genes also suggested connections to intestinal epithelial barrier dysfunction, contemporary IBD drug treatment, and new actionable drug targets. A large number of genes associated with endoscopic disease severity corresponded to noncoding RNAs.

Conclusion

This study revealed biological pathways associated with IBD disease state and endoscopic disease severity, thus providing insights into the underlying mechanisms of IBD pathogenesis as well as identifying potential biomarkers and therapies. Peripheral blood might constitute a suitable noninvasive diagnostic sample type, in which gene expression profiles might serve as indicators of ongoing mucosal inflammation, and thus guide personalized treatment decisions.

Counteracting Interleukin-15 to Elucidate Its Modes of Action in Physiology and Pathology

Interleukin (IL)-15 belongs to the common gamma-dependent cytokine family, along with IL-2, IL-4, IL-7, IL-9, and IL-21. IL-15 is crucial for the homeostasis of Natural Killer (NK) and memory CD8 T cells, and to fight against cancer progression. However, dysregulations of IL-15 expression could occur and participate in the emergence of autoimmune inflammatory diseases as well as hematological malignancies. It is therefore important to understand the different modes of action of IL-15 to decrease its harmful action in pathology without affecting its beneficial effects in the immune system. In this review, we present the different approaches used by researchers to inhibit the action of IL-15, from most broad to the most selective. Indeed, it appears that it is important to selectively target the mode of action of the cytokine rather than the cytokine itself as they are involved in numerous biological processes.

Interleukin 15 in murine models of colitis

Inflammatory bowel diseases (IBDs) are characterized by abnormal, non-antigen specific chronic inflammation of unknown etiology. Genome-wide association studies show that many IBD genetic susceptibility loci map to immune function genes and compelling evidence indicate that environmental factors play a critical role in IBD pathogenesis. Clinical and experimental evidence implicate the pro-inflammatory cytokine IL-15 in the pathogenesis of IBD. IL-15 and IL-15α expression is increased in the inflamed mucosa of IBD patients. IL-15 contributes to the maintenance of different cell subsets in the intestinal mucosa. However, very few studies have addressed the role of IL-15 in pre-clinical models of colitis. In this study, we use three well-characterized models of experimental colitis to determine the contribution of IL-15 to pathological intestinal inflammation.

Selective Targeting of IL-15Rα Is Sufficient to Reduce Inflammation

Cytokines are crucial molecules for maintaining the proper functioning of the immune system. Nevertheless, a dysregulation of cytokine expression could be involved in the pathogenesis of autoimmune diseases. Interleukin (IL)-15 is a key factor for natural killer cells (NK) and CD8 T cells homeostasis, necessary to fight cancer and infections but could also be considered as a pro-inflammatory cytokine involved in autoimmune inflammatory disease, including rheumatoid arthritis, psoriasis, along with tumor necrosis factor alpha (TNF-α), IL-6, and IL-1β. The molecular mechanisms by which IL-15 exerts its inflammatory function in these diseases are still unclear. In this study, we generated an IL-15-derived molecule called NANTIL-15 (New ANTagonist of IL-15), designed to selectively inhibit the action of IL-15 through the high-affinity trimeric IL-15Rα/IL-2Rβ/γc receptor while leaving IL-15 signaling through the dimeric IL-2Rβ/γc receptor unaffected. Administrating of NANTIL-15 in healthy mice did not affect the IL-15-dependent cell populations such as NK and CD8 T cells. In contrast, we found that NANTIL-15 efficiently reduced signs of inflammation in a collagen-induced arthritis model. These observations demonstrate that the inflammatory properties of IL-15 are linked to its action through the trimeric IL-15Rα/IL-2Rβ/γc receptor, highlighting the interest of selectively targeting this receptor.

Leukemia inhibitory factor receptor homodimerization mediated by acetylation of extracellular lysine promotes prostate cancer progression through the PDPK1/AKT/GCN5 axis

BACKGROUND

Prostate cancer (PCa), an inert tumour, has a long progression period, but valid biomarkers and methods for effectively and sensitively monitoring PCa progression are lacking, prompting us to identify new predictors for diagnosis and prognosis. Posttranslational modifications characterizing receptor activation are considered potentially strong indicators of disease progression.

METHODS

The posttranscriptional regulation of leukaemia inhibitory factor receptor (LIFR) and its novel downstream signalling activity in PCa were studied using liquid mass spectrometry, genetically engineered mouse (GEM) models, organoid assays, lentivirus packaging, infection and stable cell line construction.

RESULTS

In this study, the level of acetylated K620 on LIFR in its extracellular domain was shown to predict the progression and prognosis of PCa. In PCa cells, LIFR-K620 acetylation is reversibly mediated by GCN5 and SIRT2. GEM experiments and organoid assays confirmed that the loss of LIFR-K620 acetylation inhibits PCa progression. Mechanistically, K620 acetylation facilitates LIFR homodimerization and subsequently promotes LIFR-S1044 phosphorylation and activation, which further recruits PDPK1 to activate AKT signalling and sequentially enhances the GCN5 protein level to sustain the protumour level of LIFR-K620 acetylation by preventing GCN5 degradation via CRL4Cdt2 E3 ligase.

CONCLUSIONS

Acetylation of extracellular K620 on LIFR reinforces its homodimerization and integrates the activities of PDPK1, AKT, GSK3β and GCN5 to form a novel positive feedback loop in PCa; this modification is thus a promising biomarker for monitoring PCa progression.

Interleukin-15 and cancer: some solved and many unsolved questions

Soluble interleukin (IL)-15 exists under two forms: as monomer (sIL-15) or as heterodimeric complex in association with sIL-15Rα (sIL-15/IL-15Rα). Both forms have been successfully tested in experimental tumor murine models and are currently undergoing investigation in phase I/II clinical trials. Despite more than 20 years research on IL-15, some controversial issues remain to be addressed. A first point concerns the detection of the sIL-15/IL-15Rα in plasma of healthy donors or patients with cancer and its biological significance. The second and third unsolved question regards the protumorigenic role of the IL-15/IL-15Rα complex in human cancer and the detrimental immunological consequences associated to prolonged exposure of natural killer (NK) cells to both forms of soluble IL-15, respectively. Data suggest that in vivo prolonged or repeated exposure to monomeric sIL-15 or the soluble complex may lead to NK hypo-responsiveness through the expansion of the CD8⁺/CD44⁺ T cell subset that would suppress NK cell functions. In vitro experiments indicate that soluble complex and monomeric IL-15 may cause NK hyporesponsiveness through a direct effect caused by their prolonged stimulation, suggesting that this mechanism could also be effective in vivo. Therefore, a better knowledge of IL-15 and a more appropriate use of both its soluble forms, in terms of concentrations and time of exposure, are essential in order to improve their therapeutic use. In cancer, the overproduction of sIL-15/IL-15Rα could represent a novel mechanism of immune escape. The soluble complex may act as a decoy cytokine unable to efficiently foster NK cells, or could induce NK hyporesponsiveness through an excessive and prolonged stimulation depending on the type of IL-15Rα isoforms associated. All these unsolved questions are not merely limited to the knowledge of IL-15 pathophysiology, but are crucial also for the therapeutic use of this cytokine. Therefore, in this review, we will discuss key unanswered issues on the heterogeneity and biological significance of IL-15 isoforms, analyzing both their cancer-related biological functions and their therapeutic implications.

Interleukin-15 in autoimmunity

Interleukin-15 (IL-15) is a member of the IL-2 family of cytokines, which use receptor complexes containing the common gamma (γ_c) chain for signaling. IL-15 plays important roles in innate and adaptative immune responses and is implicated in the pathogenesis of several immune diseases. The IL-15 receptor consists of 3 subunits namely, the ligand-binding IL-15Rα chain, the β chain (also used by IL-2) and the γ_c chain. IL-15 uses a unique signaling pathway whereby IL-15 associates with IL-15Rα during biosynthesis, and this complex is 'trans-presented' to responder cells that expresses the IL-2/15Rβγ_c receptor complex. IL-15 is subject to post-transcriptional and post-translational regulation, and evidence also suggests that IL-15 cis-signaling can occur under certain conditions. IL-15 has been implicated in the pathology of various autoimmune diseases such as rheumatoid arthritis, autoimmune diabetes, inflammatory bowel disease, coeliac disease and psoriasis. Studies with pre-clinical models have shown the beneficial effects of targeting IL-15 signaling in autoimmunity. Unlike therapies targeting other cytokines, anti-IL-15 therapies have not yet been successful in humans. We discuss the complexities of IL-15 signaling in autoimmunity and explore potential immunotherapeutic approaches to target the IL-15 signaling pathway.

Pre-Treatment Biomarkers of Anti-Tumour Necrosis Factor Therapy Response in Crohn's Disease-A Systematic Review and Gene Ontology Analysis

The most prominent treatment for the serious cases of Crohn’s disease (CD) are biological tumour necrosis factor (TNF) inhibitors. Unfortunately, therapy nonresponse is still a serious issue in ~1/3 of CD patients. Accurate prediction of responsiveness prior to therapy start would therefore be of great value. Clinical predictors have, however, proved insufficient. Here, we integrate genomic and expression data on potential pre-treatment biomarkers of anti-TNF nonresponse. We show that there is almost no overlap between genomic (annotated with tissue-specific expression quantitative trait loci data) and transcription (RNA and protein data) biomarkers. Furthermore, using interaction networks we demonstrate there is little direct interaction between the proposed biomarkers, though a majority do have common interactors connecting them into networks. Our gene ontology analysis shows that these networks have roles in apoptotic signalling, response to oxidative stress and inflammation pathways. We conclude that a more systematic approach with genome-wide search of genomic and expression biomarkers in the same patients is needed in future studies.

Frequencies of IL-15Rα+ cells in patients with Behçet's disease and the effects of overexpressing IL-15Rα+ on disease symptoms in mice

It has been suggested higher serum levels of IL-15 and lower expression levels of IL-15 receptor alpha (IL-15Rα) are correlated with pathogenesis of Behçet's disease (BD). However, whether overexpressing IL-15Rα could be used as a therapeutic candidate for BD is currently unclear. Therefore, the purpose of this study was to determine whether overexpressing IL-15Rα could affect BD symptoms in a mouse model. IL-15/IL-15Rα complex expressing vector or protein complex of IL-15/IL-15Rα-Fc was used to treat BD mice. Frequencies of IL-15Rα+ cells in peripheral blood leukocytes (PBL) and lymph node cells were determined using a flow cytometer. BD symptoms in mice improved after treatment with IL-15/15Rα expression vector or IL-15/IL-15Rα-Fc protein complex. In addition, treatment with pIL-15/15Rα significantly (p = .016) decreased disease severity score of BD mice compared to treatment with control vector. Frequencies of IL-15Rα+ cells were also significantly (p = .01) higher in peritoneal macrophages of pIL-15/15Rα treated BD mice than those of mice treated with control vector. Frequencies of IL-15Rα+ PBL were also significantly higher in BD mice treated with IL-15/IL-15Rα-Fc protein complex than those in the control group. These results suggest up-regulating IL-15Rα+ cells could be used as novel therapeutic strategies to control BD in the future.

T helper type 1-related molecules as well as interleukin-15 are hyperexpressed in the skin lesions of patients with pyoderma gangrenosum

Pyoderma gangrenosum (PG) is a rare, immune-mediated skin disease classified into the group of neutrophilic dermatoses. Although a number of studies confirmed the central role of innate immunity, only few studies have investigated the possible contributing role of acquired immunity. In particular, no reports concerning T helper type 1 (Th1) and Th2 cells are available as yet. Therefore, 15 patients with PG, five with Sweet's syndrome (SS) and nine skin specimens from healthy controls (HC) were investigated, evaluating the expression of Th1-related markers interleukin (IL)-12, interferon (IFN)-γ, C-X-C motif chemokine receptor 3 (CXCR3) and C-C motif chemokine receptor 5 (CCR5), of the Th2-related molecules IL-4, IL-5, IL-13 and CCR3, of the co-stimulatory axis CD40/CD40 ligand, of IL-15 and the natural killer (NK) cell marker CD56 in skin lesions by immunohistochemistry. Patients with PG and SS showed a higher expression of Th1 markers than HC. Conversely, IL-5- and CCR3-expressing cells were less numerous in PG skin lesions compared to SS (P = 0·0157 and < 0·0001, respectively). Both CD40 and CD40L were expressed more in PG than in SS and HC (P < 0·0001 for both). Finally, the number of IL-15⁺ and CD56⁺ cells was higher in the skin of patients with PG than in those of SS and HC (P < 0·0001 for both). Our results suggest that Th2 cells are down-regulated in PG. At the same time, over-expression of the co-stimulatory axis CD40/CD40L amplifies the impairment of the Th1/Th2 balance. Both these findings might explain the most aggressive behaviour of PG in comparison to SS. Moreover, over-expression of IL-15⁺ and CD56⁺ cells may suggest a possible role of NK cells in the pathogenesis of the disease.

Exaggerated IL-15 and Altered Expression of foxp3+ Cell-Derived Cytokines Contribute to Enhanced Colitis in Nlrp3-/- Mice

The pathogenesis of Crohn's disease (CD) involves defects in the innate immune system, impairing responses to microbes. Studies have revealed that mutations NLRP3 are associated with CD. We reported previously that Nlrp3−/− mice were more susceptible to colitis and exhibited reduced colonic IL-10 expression. In the current study, we sought to determine how the loss of NLRP3 might be altering the function of regulatory T cells, a major source of IL-10. Colitis was induced in wild-type (WT) and Nlrp3−/− mice by treatment with dextran sulphate sodium (DSS). Lamina propria (LP) cells were assessed by flow cytometry and cytokine expression was assessed. DSS-treated Nlrp3−/− mice exhibited increased numbers of colonic foxp3+ T cells that expressed significantly lower levels of IL-10 but increased IL-17. This was associated with increased expression of colonic IL-15 and increased surface expression of IL-15 on LP dendritic cells. Neutralizing IL-15 in Nlrp3−/− mice attenuated the severity of colitis, decreased the number of colonic foxp3+ cells, and reduced the colonic expression of IL-12p40 and IL-17. These data suggest that the NLRP3 inflammasome can regulate intestinal inflammation through noncanonical mechanisms, providing additional insight as to how NLRP3 variants may contribute to the pathogenesis of CD.

IL-15: a central regulator of celiac disease immunopathology

Interleukin-15 (IL-15) exerts many biological functions essential for the maintenance and function of multiple cell types. Although its expression is tightly regulated, IL-15 upregulation has been reported in many organ-specific autoimmune disorders. In celiac disease, an intestinal inflammatory disorder driven by gluten exposure, the upregulation of IL-15 expression in the intestinal mucosa has become a hallmark of the disease. Interestingly, because it is overexpressed both in the gut epithelium and in the lamina propria, IL-15 acts on distinct cell types and impacts distinct immune components and pathways to disrupt intestinal immune homeostasis. In this article, we review our current knowledge of the multifaceted roles of IL-15 with regard to the main immunological processes involved in the pathogenesis of celiac disease.

Role for therapeutic drug monitoring during induction therapy with TNF antagonists in IBD: evolution in the definition and management of primary nonresponse

: Primary nonresponse and primary nonremission are important limitations of tumor necrosis factor (TNF) antagonists, occurring in 10% to 40% and 50% to 80% of patients with inflammatory bowel disease, respectively. The magnitude of primary nonresponse differs between phase III clinical trials and cohort studies, indicating differences, e.g., in definition, patient population or blinding. The causes of nonresponse can be attributed to the drug (pharmacokinetics, immunogenicity), the patient (genetics, disease activity), the disease (type, location, severity), and/or the treatment strategy (dosing regimen, combination therapy). Primary nonresponse has been attributed to "non-TNF-driven disease" which is an overly simplified and potentially misleading approach to the problem. Many patients with primary nonresponse could successfully be treated with dose optimization during the induction phase or switching to another TNF antagonist. Therefore, primary nonresponse is frequently not a non-TNF-driven disease. Recent studies from rheumatoid arthritis and preliminary data from inflammatory bowel disease evaluating therapeutic drug monitoring have suggested that early measurement of drug and anti-drug antibody concentrations could help to define primary nonresponse and rationalize patient management of this problem. Moreover, a modeling approach including pharmacological parameters and patient-related covariants could potentially be predictive for response to the treatment. We describe an overview of this evolution in thinking, underpinned by previous findings, and assess the potential role of early measurement of drug and antidrug antibody concentrations in the definition and management of primary nonresponse.

IL-15: a central regulator of celiac disease immunopathology

Interleukin-15 (IL-15) exerts many biological functions essential for the maintenance and function of multiple cell types. Although its expression is tightly regulated, IL-15 upregulation has been reported in many organ-specific autoimmune disorders. In celiac disease, an intestinal inflammatory disorder driven by gluten exposure, the upregulation of IL-15 expression in the intestinal mucosa has become a hallmark of the disease. Interestingly, because it is overexpressed both in the gut epithelium and in the lamina propria, IL-15 acts on distinct cell types and impacts distinct immune components and pathways to disrupt intestinal immune homeostasis. In this article, we review our current knowledge of the multifaceted roles of IL-15 with regard to the main immunological processes involved in the pathogenesis of celiac disease.

Epidermal IL-15Rα acts as an endogenous antagonist of psoriasiform inflammation in mouse and man

Stromal cells at epithelial surfaces contribute to innate immunity by sensing environmental danger signals and producing proinflammatory cytokines. However, the role of stromal cells in controlling local inflammation is unknown. We show that endogenous soluble IL-15 receptor α (IL-15Rα) derived from epidermal stroma, notably keratinocytes, protects against dendritic cell/IL-15-mediated, T cell-driven skin inflammation in vivo, and is relevant to human psoriasis. Selective lack of IL-15Rα on stromal epidermal cells exacerbated psoriasiform inflammation in animals. Epidermal IL-15Rα was shed by keratinocytes via proteolytic cleavage by matrix metalloproteinases upon stimulation with proinflammatory cytokines to counteract IL-15-induced proliferation of IL-17(+) αβ and γδ T cells and production of TNF, IL-23, IL-17, and IL-22 during skin inflammation. Notably, administration of soluble IL-15Rα was able to repress secretion of IL-1β, IL-6, and TNF by keratinocytes, dampen expansion of IL-17(+) αβ and γδ T cells in vivo, and prevent psoriasis in two mouse models, including human xenograft AGR mice. Serum levels of soluble IL-15Rα negatively correlated with disease severity, and levels rose upon successful treatment of psoriasis in patients. Thus, stressed epidermal stromal cells use soluble IL-15Rα to dampen chronic inflammatory skin disease.

The role of IL-15 in gastrointestinal diseases: a bridge between innate and adaptive immune response

IL-15 is a member of the IL-2 family of cytokines whose signaling pathways are a bridge between innate and adaptive immune response. IL-15 is part of the intestinal mucosal barrier, and functions to modulate gut homeostasis. IL-15 has pivotal roles in the control of development, proliferation and survival of both innate and adaptive immune cells. IL-15 becomes up-regulated in the inflamed tissue of intestinal inflammatory disease, such as IBD, Celiac Disease and related complications. Indeed, several studies have reported that IL-15 may participate to the pathogenesis of these diseases. Furthermore, although IL-15 seems to be responsible for inflammation and autoimmunity, it also may increase the immune response against cancer. For these reasons, we decided to study the intestinal mucosa as an 'immunological niche', in which immune response, inflammation and local homeostasis are modulated. Understanding the role of the IL-15/IL-15R system will provide a scientific basis for the development of new approaches that use IL-15 for immunotherapy of autoimmune diseases and malignancies. Indeed, a better understanding of the complexity of the mucosal immune system will contribute to the general understanding of immuno-pathology, which could lead to new therapeutical tools for widespread immuno-mediated diseases.

Interleukin-15 receptor α expression in inflammatory bowel disease patients before and after normalization of inflammation with infliximab

Interleukin-15 (IL-15) is a pro-inflammatory cytokine thought to contribute to the inflammation in inflammatory bowel diseases (IBD). The specific receptor chain IL-15Rα can be expressed as a transmembranous signalling receptor, or can be cleaved by a disintegrin and metalloprotease domain 17 (ADAM17) into a neutralizing, soluble receptor (sIL-15Rα). The aim of this study is to evaluate the expression of IL-15Rα in ulcerative colitis (UC) and Crohn's disease (CD) patients before and after infliximab (IFX) therapy. Gene expression of IL-15Rα, IL-15 and ADAM17 was measured at the mRNA level by quantitative reverse transcription-PCR in mucosal biopsies harvested before and after first IFX therapy. Concentrations of sIL-15Rα were measured in sera of patients by ELISA and IL-15Rα protein was localized in the gut by immunohistochemistry and immunofluorescence. Mucosal expression of IL-15Rα is increased in UC and CD patients compared with controls and it remains elevated after IFX therapy in both responder and non-responder patients. The concentration of sIL-15Rα in serum is also increased in UC patients when compared with controls and does not differ between responders and non-responders either before or after IFX. CD patients have levels of sIL-15Rα comparable to healthy controls before and after therapy. In mucosal tissues, IL-15Rα(+) cells closely resemble activated memory B cells with a pre-plasmablastic phenotype. To conclude, IBD patients have an increased expression of IL-15Rα mRNA in the mucosa. Expression is localized in B cells, suggesting that IL-15 regulates B-cell functions during bowel inflammation. No change in release of sIL-15Rα is observed in patients treated with IFX.

Sarcopenia, obesity, and natural killer cell immune senescence in aging: altered cytokine levels as a common mechanism

Human aging is characterized by both physical and physiological frailty. A key feature of frailty, sarcopenia is the age-associated decline in skeletal muscle mass, strength, and endurance that characterize even the healthy elderly. Increases in adiposity, particularly in visceral adipose tissue, are almost universal in aging individuals and can contribute to sarcopenia and insulin resistance by increasing levels of inflammatory cytokines known collectively as adipokines. Aging also is associated with declines in adaptive and innate immunity, known as immune senescence, which are risk factors for cancer and all-cause mortality. The cytokine interleukin-15 (IL-15) is highly expressed in skeletal muscle tissue and declines in aging rodent models. IL-15 inhibits fat deposition and insulin resistance, is anabolic for skeletal muscle in certain situations, and is required for the development and survival of natural killer (NK) lymphocytes. We review the effect that adipokines and myokines have on NK cells, with special emphasis on IL-15. We posit that increased adipokine and decreased IL-15 levels during aging constitute a common mechanism for sarcopenia, obesity, and immune senescence.

Clinical use and mechanisms of infliximab treatment on inflammatory bowel disease: a recent update

The pathogenesis and treatment of inflammatory bowel disease (IBD) have been recently advanced, while it is still challenged with high morbidity and poor prognosis. Infliximab, a monoclonal antibody of tumor necrosis factor (TNF), has emerged as an efficient treatment with many clinical benefits such as quick disease activity reduction and IBD patient life quality improvement. However, the biological effects of infliximab on IBD need to be elucidated. This paper reviewed the clinical use and recently advanced biological action of infliximab on IBD. By forming the stable complex with the soluble or the membrane form of TNF in fluid environment or on cell surface of immune cell, fibroblast, endothelium, and epithelium, infliximab quenches TNF activity and performs the important biological actions which lead to amelioration and remission of immune responses. The mechanisms of infliximab treatment for IBD were intensively discussed. The recent advances on two topics including predictors and side effects of infliximab treatment were also reviewed.

Regulating the immune system via IL-15 transpresentation

Transpresentation has emerged as an important mechanism mediating IL-15 responses in a subset of lymphocytes during the steady state. In transpresentation, cell surface IL-15, bound to IL-15Rα is delivered to opposing lymphocytes during a cell-cell interaction. The events most dependent on IL-15 include the development and homeostasis of memory CD8 T cells, Natural Killer cells, invariant Natural Killer T cells, and intraepithelial lymphocytes. As lymphocyte development and homeostasis involve multiple steps and mechanisms, IL-15 transpresentation can have diverse roles throughout. Moreover, distinct stages of lymphocyte differentiation require IL-15 transpresented by different cells, which include both hematopoietic and non-hematopoietic cell types. Herein, we will describe the points where IL-15 transpresentation impacts these processes, the specific cells thought to drive IL-15 responses, as well as their role in the course of development and homeostasis.

Interleukin-15-dependent NKp46+ innate lymphoid cells control intestinal inflammation by recruiting inflammatory monocytes

With the goal in mind to define how interleukin-15 (IL-15) contributes to acute intestinal inflammation, we have used a mouse model of ileitis induced by oral infection with Toxoplasma gondii. We observed that a crosstalk between IL-15 and interleukin-18 (IL-18) promoted intestinal recruitment of inflammatory monocytes, where these cells participated in parasite control but also in tissue damage. A stromal source of IL-15 controlled the development of lamina propria NKp46(+)NK1.1(+) cells, whereas IL-18 produced during T. gondii infection stimulated their production of the chemokine CCL3. In turn, CCL3 attracted inflammatory monocytes via their chemokine receptor CCR1, which was indispensable for their recruitment into the inflamed gut. Collectively, these results identify the IL-15-dependent subset of intestinal NKp46(+) cells as an important source of CCL3, which can amplify intestinal inflammation via the recruitment of CCR1(+) inflammatory monocytes. Preliminary evidence suggests that this pathway might operate in Crohn's disease.

Inflammatory bowel disease and colitis: new concepts from the bench and the clinic

PURPOSE OF REVIEW

The previous 18 months have shown important progress in unravelling the causes of inflammatory bowel disease (IBD) and in improving its management for the patients.

RECENT FINDINGS

More genome-wide association studies and meta-analyses of these have been published and have identified more than 100 confirmed genes for IBD, and highlighted a number of novel pathways. Two of the genes, NOD2/CARD15 and the autophagy gene ATG16L1 have recently been linked into one functional pathway of bacterial sensing, invasion and elimination. From the clinical side, the previous year has been dominated mainly by the results of the SONIC study, comparing efficacy and safety of azathioprine, infliximab and the combination of azathioprine and infliximab, in patients with active Crohn's disease, naive to these drugs. International consensus guidelines on infection prevention were released last year by the European Crohn's and Colitis Organisation.

SUMMARY

The recent findings in IBD include the increasing number of IBD susceptibility genes, the demonstration that NOD2 and ATG16L1 are linked in one functional pathway and the role of IL-33/ST2 in colitis. From the bedside, the novelties have been the results of SONIC and selecting the right patient for intensified treatment with immunomodulators and anti-tumor necrosis factor, and appropriate counselling regarding risk of infections and vaccinations.

The impact of smoking in Crohn's disease: no smoke without fire

Smoking habit is the most widely accepted environmental factor affecting the incidence and disease progression in the inflammatory bowel diseases. The contrasting effects in Crohn's disease (CD) and ulcerative colitis are unexplained. The purpose of this review is to summarise the existing data on the effects of smoking in CD on disease history, recurrence after surgery, effects on drug responses and to review available evidence that carriage of some of the known susceptibility genes may be disproportionate in smokers with CD. The review also highlights potential mechanisms involved and factors that might affect patients' smoking habits. The clinical and scientific implications of the data are discussed.

Tumor necrosis factor-α monoclonal antibodies in the treatment of inflammatory bowel disease: clinical practice pharmacology

In the last 10 years, anti-tumor necrosis factor (TNF)-α therapy has become a cornerstone in the management of autoimmune diseases. Clinical trial data have consistently found that infliximab, adalimumab, and recently certolizumab pegol offer therapeutic benefits to patients with inflammatory bowel diseases (Crohn's disease and ulcerative colitis). Recent understanding on how these monoclonal antibodies evoke changes at the physiological and molecular levels have provided insights into disease pathogenesis and helped to identify new targets for future drug therapy. With increased experience in the use of these anti-TNF-α antibodies the long-term safety data, use in pregnancy have become available. This article provides an overview of the current knowledge regarding anti-TNF-α therapies for clinicians caring for patients with Crohn's disease and ulcerative colitis.