Immunoregulatory properties of IL-13 in patients with inflammatory bowel disease; comparison with IL-4 and IL-10

Activated monocytes with increased expression of proinflammatory cytokines play a major role in inflammatory bowel disease (IBD). Immunoregulatory cytokines such as IL-4 and IL-10 can effectively suppress the proinflammatory response of activated monocytes. IL-13 is a recently described antiinflammatory agent in vitro. The aim of our study was to determine the in vitro immunosuppressive capacity of IL-13, IL-4 and IL-10 in patients with IBD. Peripheral blood monocytes were isolated from 27 patients with ulcerative colitis (UC), 27 patients with Crohn's disease (CD) and 16 healthy controls. Cells were stimulated with pokeweed mitogen (PWM) after treatment with IL-13, IL-4 and IL-10, and secretion of IL-1β, tumour necrosis factor-alpha (TNF-α) and IL-6 was assessed using sandwich ELISA systems. Peripheral blood monocytes secreted significantly increased amounts of TNF-α and IL-6 under stimulation with PWM in patients with CD, while UC patients showed significantly elevated levels of IL-1β. The antiinflammatory cytokines IL-13, IL-4 and IL-10 were all capable of inhibiting monocyte secretion of IL-1β in a dose-dependent manner. With regard to IL-13 and IL-4, there was no significant suppression of TNF-α and IL-6 in patients with active IBD. By contrast, IL-10 was able to down-regulate all proinflammatory cytokines in active IBD as well as in controls. Proinflammatory cytokines from patients with inactive IBD could be significantly down-regulated by all three immunoregulatory cytokines. The inhibitory effect of IL-13 on TNF-α and IL-6 production in differentiated macrophages was diminished in IBD patients, as well as in controls. In disease controls we also observed a reduced inhibition of TNF-α and IL-6 after treatment with IL-13. In conclusion, the antiinflammatory activity of IL-13 is partially reduced in patients with active IBD. The hyporesponsiveness of activated and differentiated monocytes to IL-13 and IL-4 does not seem to be a disease-specific phenomenon.     

Circulating antiinflammatory cytokine IL-10 in patients with inflammatory bowel disease (IBD).

IBD is characterized by increased serum concentrations of different cytokines. IL-10 inhibits the production of proinflammatory cytokines such as IL-1, tumour necrosis factor-alpha (TNF-a), interferon-gamma (IFN-gamma) and IL-6 through inhibitory action on Th1 cells and macrophages, and it is thought to be a suppressor type cytokine. In the present study we determined serum concentrations of IL-10 in patients with ulcerative colitis (UC) and Crohn's disease (CD). We measured human IL-10 by our own newly established ELISA system using PharMingen antibodies. Serum antibodies were assessed in 44 patients with UC, 40 patients with CD, and in 30 healthy controls. Human IL-10 serum levels were significantly increased in patients with active UC (144 +/- 34 pg/ml (mean +/- s.e.m.), P < 0.001) and in active CD (132 +/- 32 pg/ml, P < 0.001) compared with healthy controls (44 +/- 9.5 pg/ml). Only patients with active CD and active UC presented with significantly increased IL-10 serum levels, while patients with inactive disease did not show any significant increase. There was no statistically significant difference between IL-10 serum levels in patients with CD or UC. Compared with clinical disease activity indices there was a significant correlation between IL-10 serum concentration and CDAI in patients with CD (r = 0.45, P < 0.01) and CAI in UC patients (r = 0.39, P < 0.05). Comparing IL-10 serum levels with serum concentrations of other proinflammatory cytokines there was a significant correlation to serum levels of sIL-2R (r = 0.417, P < 0.05) and IL-6 (r = 0.387, P < 0.05) in patients with CD. Serum cytokine levels in patients with UC did not show any significant correlation to IL-10 serum concentration. IL-10 is elevated in serum of patients with active CD and UC, suggesting that IL-10 acts as a naturally occurring damper in the acute inflammatory process of IBD.     

Mannose-capped lipoarabinomannan-induced B10 cells decrease severity of dextran sodium sulphate-induced inflammatory bowel disease in mice

Inflammatory bowel disease (IBD) is a chronic, non-specific, inflammatory gastrointestinal disease that mainly consists of Crohn's disease and ulcerative colitis. However, the aetiology and pathogenesis of IBD are still unclear. B10 (IL-10 producing regulatory B) cells, a subset of regulatory B cells, are known to contribute to intestinal homeostasis and the aberrant frequency of B10 cells is associated with IBD. We have recently reported that B10 cells can be induced by ManLAM (mannose-capped lipoarabinomannan), a major cell-wall lipoglycan of M tb (Mycobacterium tuberculosis). In the current study, the ManLAM-induced B10 cells were adoptively transferred into IL(interleukin)-10^−/− mice and the roles of ManLAM-induced B10 cells were investigated in DSS (dextran sodium sulphate)-induced IBD model. ManLAM-induced B10 cells decrease colitis severity in the mice. The B10 cells downregulate Th1 polarization in spleen and MLNs (mesenteric lymph nodes) of DSS-treated mice. These results suggest that IL-10 production by ManLAM-treated B cells contributes to keeping the balance between CD4⁺ T cell subsets and protect mice from DSS-induced IBD.     

Very early onset inflammatory bowel disease: Investigation of the IL-10 signaling pathway in Iranian children

Background & aimComparing to adult inflammatory bowel disease (IBD), those with early onset manifestations have different features in terms of the underlying molecular pathology, the course of disease and the response to therapy. We investigated the IL-10 signaling pathway previously reported as an important cause of infantile (Very Early Onset) IBD to find any possible variants.MethodWith the next generation sequencing technique we screened IL-10, IL-10RA and IL10RB genes of 15 children affected by very early onset-GI (gastrointestinal) disorders. Additionally, we analyzed them based on Thermo Fisher immune deficiency panel for genes either having a known role in IBD pathogenesis or cause the disorders with overlapping manifestations. We performed multiple functional analyses only for the cases showing variants in IL-10- related genes.ResultIn 3 out of 15 patients we identified variants including a homozygous and heterozygote mutations in IL-10RA and a novel homozygous mutation in IL-12RB1. Our functional studies reveal that in contrast to the IL-10RA heterozygote mutation that does not have deleterious effects, the homozygous mutation abrogates the IL-10 signaling pathway.ConclusionOur study suggests we need to modify the classical diagnostic approach from functional assays followed by candidate- gene or genes sequencing to the firstly parallel genomic screening followed by functional studies.     

Innate mucosal‐associated invariant T (MAIT) cells are activated in inflammatory bowel diseases

Inflammatory bowel diseases are characterized by a deregulated immune response targeting the gut bacterial flora. Mucosal‐associated invariant T (MAIT) cells are major histocompatibility complex (MHC) class Ib‐restricted innate‐like lymphocytes with anti‐bacterial functions. They display an effector/memory phenotype and are found in large numbers in the blood, mucosae and liver. They have also been implicated in inflammatory diseases such as multiple sclerosis. Therefore, we aimed to analyse the possible involvement of MAIT cells in Crohn's disease (CD) and ulcerative colitis (UC). To this end, a phenotypical and functional analysis of MAIT cells isolated from the blood of healthy subjects, CD and UC patients was undertaken. MAIT cells were also quantified in ileal biopsies of CD patients. The frequency of blood MAIT cells was specifically reduced in IBD patients compared with healthy donors, whereas it was dramatically greater in the inflamed versus healthy tissue. MAIT cells were activated as they expressed significantly more the Ki67 antigen, and this was accompanied by phenotypical changes such as increased expression of natural killer (NK)G2D and B and T lymphocyte attenuator (BTLA). Finally, in‐vitro‐activated MAIT cells from CD and UC patients secreted significantly more interleukin (IL)‐17, together with a decreased interferon (IFN)‐γ in CD but an increased IL‐22 in UC. These data show that MAIT cells are activated in IBD, which results in an increased recruitment towards the inflamed tissues, an altered phenotype and a switch in the pattern of cytokine secretion. This is the first demonstration that MAIT cells are immune players in IBD, whose precise functions in this context need to be addressed.     

The effects of CD40- and interleukin (IL-4)-activated CD23+ cells on the production of IL-10 by mononuclear cells in Graves' disease: the role of CD8+ cells

The possible roles of CD8+ cells in the abnormal T cell-dependent B-cell activation in Graves' disease were investigated by analysing lymphocyte subsets in peripheral blood mononuclear cells (PBMC) and their production of soluble factors and cytokines such as IL-10 in patients with Graves' disease, Hashimoto's thyroiditis and normal controls. The PBMC were separated into CD8+ and CD8-depleted cells by magnetic separation columns, and cultured for 7 days with or without anti-CD40 monoclonal antibodies and IL-4. The culture supernatant was assayed for sCD23 and IL-10 using EIA, and the remaining cells were analysed by flow cytometry. Stimulation with anti-CD40 antibody together with IL-4 increased sCD23 levels and the number of CD23+ cells. The latter was further augmented by depletion of CD8+ cells. This combination of B cell stimulants increased production of IL-10 by PBMC from patients with Graves' disease. The CD40- and IL-4-activated production of IL-10 was decreased by CD8+ cell depletion. In contrast, constitutive production of IL-10 was increased after CD8+ cell depletion in a group of patients with low basal secretion levels (<35 ng/ml). It was, however, decreased in a group with higher basal production levels, but such a relationship was not found in the normal control group. Thus, T cell-dependent B-cell activation via a CD40 pathway activates CD23+ cells, leading to over-production of IL-10 and a shift of the Th1/Th2 balance to Th2 dominance, while CD8+ cells may suppress this activation to counteract the Th2 deviation in Graves' disease.     

Anti-inflammatory effects of probiotic yogurt in inflammatory bowel disease patients

Our aim was to assess anti-inflammatory effects on the peripheral blood of subjects with inflammatory bowel disease (IBD) who consumed probiotic yogurt for 1 month. We studied 20 healthy controls and 20 subjects with IBD, 15 of whom had Crohn's disease and five with ulcerative colitis. All the subjects consumed Lactobacillus rhamnosus GR-1 and L. reuteri RC-14 supplemented yogurt for 30 days. The presence of putative regulatory T (T(reg)) cells (CD4(+) CD25(high)) and cytokines in T cells, monocytes and dendritic cells (DC) was determined by flow cytometry from peripheral blood before and after treatment, with or without ex vivo stimulation. Serum and faecal cytokine concentrations were determined by enzyme-linked immunosorbent assays. The proportion of CD4(+) CD25(high) T cells increased significantly (P = 0.007) in IBD patients, mean (95% confidence interval: CI) 0.84% (95% CI 0.55-1.12) before and 1.25% (95% CI 0.97-1.54) after treatment, but non-significantly in controls. The basal proportion of tumour necrosis factor (TNF)-alpha(+)/interleukin (IL)-12(+) monocytes and myeloid DC decreased in both subject groups, but of stimulated cells only in IBD patients. Also serum IL-12 concentrations and proportions of IL-2(+) and CD69(+) T cells from stimulated cells decreased in IBD patients. The increase in CD4(+) CD25(high) T cells correlated with the decrease in the percentage of TNF-alpha- or IL-12-producing monocytes and DC. The effect of the probiotic yogurt was confirmed by a follow-up study in which subjects consumed the yogurt without the probiotic organisms. Probiotic yogurt intake was associated with significant anti-inflammatory effects that paralleled the expansion of peripheral pool of putative T(reg) cells in IBD patients and with few effects in controls.     

乙肝疫苗无、弱应答与B7-CD28及IL-12、IL-10的相关性

目的：研究乙肝疫苗无、弱应答与B7-CD28分子及IL-12、IL-10的相关性。方法：分离并培养乙肝疫苗强应答和无、弱应答者PBMCs，以PHA或rHBsAg刺激。用流式细胞术检测培养细胞CD80、CD86及CD28的表达；酶标法检测上清IL-12、IL-10的水平；MTT法检测细胞增殖反应。结果：rHRsAg刺激后，无、弱应答组和强应答组比较，CD80和CD86的表达率、IL-12和IL-10水平、细胞增殖反应均降低，差异显著；但CD4^ 、CD8^ 细胞CD28的表达率无显著差异。PHA刺激后，上述指标在2组之间均无显著差异。结论：乙肝疫苗无、弱应答者一般的细胞免疫功能正常。抗-HBs低下与CD80、CD86表达及IL-12、IL-10产生不足等有关，但无T细胞CD28的表达缺陷。     

IL-10 enhances IL-2-induced proliferation and cytotoxicity by human intestinal lymphocytes

IL-10 modulation of human intestinal T lymphocyte functions was studied for the first time. Lymphocyte proliferation was determined by 3H-thymidine incorporation; cytokine production, by ELISA; expression of surface markers, by immunofluorescence and flow cytometric analysis; and cytotoxicity, by lysis of 51Cr-labelled target cells. IL-10 blocked phytohaemagglutinin (PHA)-induced activation and proliferation of CD8+ T cells from the epithelium and lamina propria. It was a greater inhibitor of IL-2, interferon-gamma, and tumour necrosis factor-alpha production than were IL-4 or transforming growth factor-beta. In contrast, IL-10 enhanced IL-2-stimulated proliferation of both CD4+ and CD8+ T cells by increasing cell division after activation. It also augmented IL-2- but not IL-15-induced cytotoxicity of intestinal lymphocytes against colon cancer by a mechanism independent of natural killer cells. In conclusion, IL-10 blocking of proinflammatory cytokine secretion probably reduces intestinal inflammation. IL-10 augmentation of IL-2-induced cytotoxicity may help to maintain host defence.     

Changes in neuropeptide-containing nerves in human colonic mucosa with inflammatory bowel disease

The distribution abnormality of vasoactive intestinal polypeptide-containing nerves (VIP-nerves) and substance P-containing nerves (SP-nerves) was immunohistochemically investigated in the colonic mucosa with inflammatory bowel disease (IBD) in relation to colonic glands and blood vessels In the lamina propria. In active ulcerative colitis (UC), VIP- and SP-nerves decreased in severe inflammatory lesions. VIP-nerves were almost absent particularly around crypt abscesses. Even In resolving and quiescent UC, VIP-nerves still decreased, depending on the decrease of glands and blood vessels. On the other hand, both nerves Increased in some hypervascular lesions. In the uninvolved mucosa of UC, they did not change their distribution. In Crohn's disease, the distribution abnormality of both nerves resembled that of UC. These results suggest that the changes in VIP-and SP-nerve distributions in the mucosa with IBD are subsequent to mucosal inflammation and damage. However, these peptides are known to be immunoregulators, and their distribution abnormalities may induce the disorder of immunoregulation in the IBD mucosa and cause the mucosal damage and/or chronicity.     

Human gingiva‐derived mesenchymal stem cells alleviate inflammatory bowel disease via IL‐10 signalling‐dependent modulation of immune cells

Current evidence indicates that inflammatory bowel disease (IBD) is caused primarily by impaired mucosal immunity, resulting in an imbalance between epithelial barrier function and tissue inflammation. Human gingiva‐derived mesenchymal stem cells (GMSCs) exhibit immunomodulatory and anti‐inflammatory effects in a variety of immunity‐ and inflammation‐associated diseases. However, the role of GMSCs in treating IBD has not been elucidated. Our study, therefore, examined the therapeutic effect and mechanism of GMSCs in a murine colitis model of IBD. Our results indicate that the infusion of GMSCs significantly prolonged survival and relieved symptoms. Phenotype analyses showed that the frequencies of NK1.1⁺ and CD11b⁺ cells, as well as CD4 T cells in the spleen, were suppressed in GMSC‐treated mice compared with the PBS‐ or fibroblast‐treated control groups. Additionally, GMSC treatment markedly increased the numbers of interleukin (IL)‐10⁺ regulatory T cells, reduced the secretion of pro‐inflammatory cytokines, and increased production of anti‐inflammatory cytokines. A mechanistic study revealed that anti‐IL‐10R antibody abolished the protective effect of GMSCs compared with mice treated with anti‐IgG antibody. Thus, our results indicate that GMSCs play a critical role in alleviating colitis by modulating inflammatory immune cells via IL‐10 signalling.     

Enteroglial cells act as antigen-presenting cells in chagasic megacolon

Chagas disease is one of the most serious parasitic diseases of Latin America, with a social and economic impact far outweighing the combined effects of other parasitic diseases such as malaria, leishmaniasis, and schistosomiasis. In the chronic phase of this disease, the destruction of enteric nervous system components leads to megacolon development. Besides neurons, the enteric nervous system is constituted by enteric glial cells, representing an extensive but relatively poorly described population within the gastrointestinal tract. Several lines of evidence suggest that enteric glial cells represent an equivalent of central nervous system astrocytes. Previous data suggest that enteric glia and neurons are active in the enteric nervous system during intestinal inflammatory and immune responses. To evaluate whether these cells act as antigen-presenting cells, we investigated the expression of molecules responsible for activation of T cells, such as HLA-DR complex class II and costimulatory molecules (CD80 and CD86), by neurons and enteric glial cells. Our results indicate that only enteric glial cells of chagasic patients with megacolon express HLA-DR complex class II and costimulatory molecules, and hence they present the attributes necessary to act as antigen-presenting cells.     

IL-23 up-regulates IL-10 and induces IL-17 synthesis by polyclonally activated naive T cells in human

Interleukin (IL)-23 is a heterodimeric cytokine of the IL-12 family. Human IL-23 is known to induce interferon (IFN)-gamma production and proliferation in T cells, preferentially in the CD45RO+ memory subset. Yet, its role in the differentiation of human naive T cells remains largely unknown. We investigated the effect of recombinant human (rh)IL-23 on cord blood CD4+ and CD8+ T cells during polyclonal activation. The IL-23 receptor complex was not detectable in resting naive T cells. Nevertheless, both IL-23 receptor subunits, IL-12Rbeta1 and IL-23R, were rapidly induced after activation in both naive CD4+ and CD8+ T cells. In both cell types, rhIL-23 enhanced IFN-gamma production. This effect was demonstrable as early as 2 days after activation, illustrating that a functional IL-23 receptor is rapidly induced in naive T cells upon activation. In naive CD8+ T cells, rhIL-23 specifically induced the secretion of IL-17, a pro-inflammatory cytokine. Moreover, rhIL-23 significantly increased the production of IL-10 in both naive CD4+ and CD8+ T cells. IL-17 and IL-10 levels were not affected by the addition of rhIL-12. We conclude that IL-23 induces a specific cytokine profile, remarkably distinct from IL-12, in activated human naive T cells.     

Regulatory T-cell therapy for inflammatory bowel disease: more questions than answers

T regulatory (Treg) cells are critical for maintaining immune homeostasis and establishing tolerance to foreign, non-pathogenic antigens including those found in commensal bacteria and food. Because of their multiple suppressive mechanisms, Tregs represent a promising strategy for engineering tolerance to self and non-self antigens in chronic inflammatory diseases. Already in clinical trials in the transplantation setting, the question remains whether this therapy would be effective for the treatment of mucosal inflammatory diseases that do not pose an immediate threat to life. In this review we will discuss evidence from both animal models and patients suggesting that Treg therapy would be beneficial in the context of inflammatory bowel disease (IBD). We will examine the role of T-cell versus Treg dysfunction in IBD and discuss the putative antigens that could be potential targets of antigen-directed Treg therapy. Finally, the challenges of using Treg therapy in IBD will be discussed, with a specific emphasis on the role that the microbiota may play in the outcome of this treatment. As Treg therapy becomes a bedside reality in the field of transplantation, there is great hope that it will soon also be deployed in the setting of IBD and ultimately prove more effective than the current non-specific immunosuppressive therapies.     

Activation of invariant NK T cells protects against experimental rheumatoid arthritis by an IL-10-dependent pathway

Invariant natural killer T (iNKT) cells are a unique lymphocyte subtype implicated in the regulation of autoimmunity and a good source of protective Th2 cytokines. Agonist alpha-galactosylceramide (alpha-GalCer) of iNKT cells exert a therapeutical effect in type 1 diabetes. We investigated whether iNKT activation with alpha-GalCer was protective in collagen-induced arthritis (CIA) in DBA/1 mice, a standard model of rheumatoid arthritis. Here, we have shown that in vivo iNKT cell function was altered in DBA/1 mice since stimulation with alpha-GalCer led to decreased IL-4 and IFN-gamma levels in sera, as compared with C57BL/6 mice. alpha-GalCer induced a clear-cut diminution of clinical and histological arthritides. An anti-IL-10 receptor antibody abrogated the protective effect of alpha-GalCer, suggesting a key role for IL-10 in the protection against CIA by activated iNKT cells. Confirming these data, disease protection conferred by alpha-GalCer correlated with the ability of LN CD4+ cells to secrete larger amounts of IL-10. These findings suggest that in CIA susceptibility to autoimmunity is associated with dysfunctions of iNKT cells. Our demonstration that iNKT cell activation by alpha-GalCer remains efficient in CIA-prone DBA/1 mice to provide protective IL-10 suggests that this could be used therapeutically to treat autoimmune arthritis.     

Regulatory T cells as a therapeutic approach for inflammatory bowel disease

Foxp3⁺ T regulatory (Treg) cells suppress inflammation and are essential for maintaining tissue homeostasis. A growing appreciation of tissue-specific Treg functions has built interest in leveraging the endogenous suppressive mechanisms of these cells into cellular therapeutics in organ-specific diseases. Notably, Treg cells play a critical role in maintaining the intestinal environment. As a barrier site, the gut requires Treg cells to mediate interactions with the microbiota, support barrier integrity, and regulate the immune system. Without fully functional Treg cells, intestinal inflammation and microbial dysbiosis ensue. Thus, there is a particular interest in developing Treg cellular therapies for intestinal inflammatory disease, such as inflammatory bowel disease (IBD). This article reviews some of the critical pathways that are dysregulated in IBD, Treg cell mechanisms of suppression, and the efforts and approaches in the field to develop these cells as a cellular therapy for IBD.     

Importance of CD80/CD86-CD28 interactions in the recognition of target cells by CD8+CD122+ regulatory T cells

CD8+CD122+ regulatory T cells are a newly identified, naturally occurring type of regulatory T cell that produce interleukin-10 (IL-10) and effectively suppress interferon-gamma (IFN-gamma) production from both CD8+ and CD4+ target cells. Molecular mechanisms responsible for the recognition of target cells by CD8+CD122+ regulatory T cells were investigated in this study by using an in vitro culture system that reconstitutes the regulatory action of these cells. CD8+CD122( regulatory T cells did not produce IL-10 and did not suppress the IFN-gamma production of allogeneic target T cells when they were stimulated by immobilized anti-CD3 antibody alone, but they clearly produced IL-10 and suppressed the IFN-gamma production of target cells when stimulated by anti-CD3 plus anti-CD28-coated beads. IFN-gamma production by major histocompatibility complex-class I-deficient T cells was also suppressed by CD8+CD122+ regulatory T cells stimulated with anti-CD3 plus anti-CD28 antibody but was not suppressed by cells stimulated by anti-CD3 alone. Experiments examining the blockade of cell surface molecules expressed on either the regulatory cells or the target cells by adding specific neutralizing antibodies in the culture indicated that CD80, CD86, and CD28 molecules were involved in the regulatory action, but cytotoxic T lymphocyte antigen-4, inducible costimulatory molecule (ICOS) and programmed death-1 (PD-1) molecules were not. Finally, CD8+CD122+ cells isolated from CD28-knockout (CD28-/-) mice showed no regulatory activity. These results indicate that CD8+CD122(+) regulatory T cells recognize target T cells via the interaction of CD80/CD86-CD28 molecules to become active regulatory cells that produce suppressive factors such as IL-10.     

CD73 is a phenotypic marker of effector memory Th17 cells in inflammatory bowel disease

Purinergic signaling and associated ectonucleotidases, such as CD39 and CD73, have been implicated in the pathogenesis of inflammatory bowel disease (IBD). CD39 is known to be a Treg memory cell marker, and here we determine the phenotype and function of CD73⁺CD4⁺ T lymphocytes in patients with IBD. We describe elevated levels of CD73⁺CD4⁺ T cells in the peripheral blood and intestinal lamina propria of patients with active IBD. The functional phenotype of these CD73⁺CD4⁺ T cells was further determined by gene expression, ecto‐enzymatic activity, and suppressive assays. Increased numbers of CD73⁺CD4⁺ T cells in the periphery and lamina propria were noted during active inflammation, which returned to baseline levels following anti‐TNF treatment. Peripheral CD73⁺CD4⁺ T cells predominantly expressed CD45RO, and were enriched with IL‐17A⁺ cells. The CD73⁺CD4⁺ cell population expressed higher levels of RORC, IL‐17A, and TNF, and lower levels of FOXP3 and/or CD25, than CD73^?CD4⁺ T cells. Expression of CD73 by peripheral CD4⁺ T cells was increased by TNF, and decreased by an anti‐TNF monoclonal antibody (infliximab). In vitro, these peripheral CD73⁺CD4⁺ T cells did not suppress proliferation of CD25^? effector cells, and expressed higher levels of pro‐inflammatory markers. We conclude that the CD73⁺CD4⁺ T‐cell population in patients with active IBD are enriched with cells with a T‐helper type 17 phenotype, and could be used to monitor disease activity during treatment.     

Circulating CD4+ and CD8+ T cells are activated in inflammatory bowel disease and are associated with plasma markers of inflammation

Inflammatory bowel disease (IBD) is characterized by damage to the gut mucosa and systemic inflammation. We sought to evaluate the role of chronic inflammation on circulating T‐cell activation in human subjects with Crohn's disease and ulcerative colitis. We studied 54 patients with IBD and 28 healthy controls. T‐cell activation and cycling were assessed in whole blood samples by flow cytometry. Levels of lipopolysaccharide (LPS) were measured in serum by Limulus amoebocyte lysate assay, and plasma levels of inflammatory markers and LPS‐binding proteins were measured by ELISA. The proportions of circulating CD4⁺ and CD8⁺ T lymphocytes in cycle (Ki67⁺) are increased in patients with IBD compared with these proportions in controls. CD8⁺ T cells from patients with IBD are also enriched for cells that expressed CD38 and HLA‐DR, and proportions of these cells are related to plasma levels of interleukin‐6 and C‐reactive protein in these patients. Intracellular interleukin‐2 and interferon‐γ levels were elevated in resting and polyclonally activated CD4⁺ and CD8⁺ T cells in patients with IBD when compared with levels from healthy controls. Surprisingly, we did not find increased levels of LPS in the serum of patients with IBD. We did, however, find a signature of recent microbial translocation, as levels of LPS‐binding protein are increased in the plasma of patients with IBD compared with plasma levels in healthy controls; LPS‐binding protein levels are also directly related to proportions of CD38 HLA‐DR‐expressing CD4⁺ and CD8⁺ T cells. Local damage to the gastrointestinal tract in IBD may result in systemic inflammation and T‐cell activation.