Gut mucosal lymphocytes in inflammatory bowel disease: isolation and preliminary functional characterization

Compartment-driven imprinting of intestinal CD4 T cells in inflammatory bowel disease and homeostasis

The mucosal immune system is implicated in the etiology and progression of inflammatory bowel diseases. The lamina propria and epithelium of the gut mucosa constitute two separate compartments, containing distinct T-cell populations. Human CD4 T-cell programming and regulation of lamina propria and epithelium CD4 T cells, especially during inflammation, remain incompletely understood. We performed flow cytometry, bulk, and single-cell RNA-sequencing to profile ileal lamina propria and intraepithelial CD4 T cells (CD4CD8αα, regulatory T cells (Tregs), CD69- and CD69high Trm T cells) in controls and Crohn's disease (CD) patients (paired non-inflamed and inflamed). Inflammation results in alterations of the CD4 T-cell population with a pronounced increase in Tregs and migrating/infiltrating cells. On a transcriptional level, inflammation within the epithelium induced T-cell activation, increased IFNγ responses, and an effector Treg profile. Conversely, few transcriptional changes within the lamina propria were observed. Key regulators including the chromatin remodelers ARID4B and SATB1 were found to drive compartment-specific transcriptional programming of CD4 T(reg) cells. In summary, inflammation in CD patients primarily induces changes within the epithelium and not the lamina propria. Additionally, there is compartment-specific CD4 T-cell imprinting, driven by shared regulators, between the lamina propria and the epithelium. The main consequence of intraepithelial adaptation, irrespective of inflammation, seems to be an overall dampening of broad (pro-inflammatory) responses and tight regulation of lifespan. These data suggest differential regulation of the lamina propria and epithelium, with a specific regulatory role in the inflamed epithelium.

Omics and Multi-Omics in IBD: No Integration, No Breakthroughs

The recent advent of sophisticated technologies like sequencing and mass spectroscopy platforms combined with artificial intelligence-powered analytic tools has initiated a new era of "big data" research in various complex diseases of still-undetermined cause and mechanisms. The investigation of these diseases was, until recently, limited to traditional in vitro and in vivo biological experimentation, but a clear switch to in silico methodologies is now under way. This review tries to provide a comprehensive assessment of state-of-the-art knowledge on omes, omics and multi-omics in inflammatory bowel disease (IBD). The notion and importance of omes, omics and multi-omics in both health and complex diseases like IBD is introduced, followed by a discussion of the various omics believed to be relevant to IBD pathogenesis, and how multi-omics "big data" can generate new insights translatable into useful clinical tools in IBD such as biomarker identification, prediction of remission and relapse, response to therapy, and precision medicine. The pitfalls and limitations of current IBD multi-omics studies are critically analyzed, revealing that, regardless of the types of omes being analyzed, the majority of current reports are still based on simple associations of descriptive retrospective data from cross-sectional patient cohorts rather than more powerful longitudinally collected prospective datasets. Given this limitation, some suggestions are provided on how IBD multi-omics data may be optimized for greater clinical and therapeutic benefit. The review concludes by forecasting the upcoming incorporation of multi-omics analyses in the routine management of IBD.

Isolation of primary immune cells from fibrotic skin, esophageal, and gut tissue

Understanding the interplay between immune and structural cells is important for studying fibrosis and inflammation; however, primary immune cell isolation from organs that are typically enriched in stromal cells, like the lung, esophagus, or gut, proves to be an ongoing challenge. In fibrotic conditions, this challenge becomes even greater as infiltrating cells become trapped in the robust extracellular matrix (ECM). This protocol details a method to isolate cells at high yield from stroma-rich organs that can be used for further analyses via flow cytometry, stimulation, or culturing. Validation of this method is confirmed by flow cytometry data assessing immune cell populations of interest. This protocol can be completed in approximately 5-6 h.

The elusive case of human intraepithelial T cells in gut homeostasis and inflammation

The epithelial barrier of the gastrointestinal tract is home to numerous intraepithelial T cells (IETs). IETs are functionally adapted to the mucosal environment and are among the first adaptive immune cells to encounter microbial and dietary antigens. They possess hallmark features of tissue-resident T cells: they are long-lived nonmigratory cells capable of rapidly responding to antigen challenges independent of T cell recruitment from the periphery. Gut-resident T cells have been implicated in the relapsing and remitting course and persisting low-grade inflammation of chronic gastrointestinal diseases, including IBD and coeliac disease. So far, most data IETs have been derived from experimental animal models; however, IETs and the environmental makeup differ between mice and humans. With advances in techniques, the number of human studies has grown exponentially in the past 5 years. Here, we review the literature on the involvement of human IETs in gut homeostasis and inflammation, and how these cells are influenced by the microbiota and dietary antigens. Finally, targeting of IETs in therapeutic interventions is discussed. Broad insight into the function and role of human IETs in gut homeostasis and inflammation is essential to identify future diagnostic, prognostic and therapeutic strategies.

An Optimized and Validated Method for Isolation and Characterization of Lymphocytes from HIV+ Human Gut Biopsies

The gastrointestinal (GI) tract harbors most of the body's immune cells and is also a major HIV reservoir in ART-treated patients. To achieve a cure, most HIV-infected cells must be identified and eliminated. While obtaining gut biopsies is a relatively noninvasive method of sampling relevant tissue for monitoring HIV activity, immune cell isolation from these limited tissue samples has proven to be challenging. Enzymatic tissue digestion is required for maximal immune cell isolation from gut biopsies. However, these enzymatic digestions can also be detrimental for preservation of cellular surface markers that are required for accurate identification of various subsets of leukocytes. In this study, we describe an optimized protocol for isolation of lymphocytes from human gut biopsies. We also discuss our validation results, which show that compared with several other collagenase preparations, the use of CSLPA maintains high lymphocyte recovery while preserving the integrity of most cellular surface antigens that we tested. Importantly, chemokine receptors that are used to characterize various subsets of T cells, which are notorious for being digested during a typical enzymatic tissue digestion, are highly preserved using this protocol.

Inflammation-induced endothelial-to-mesenchymal transition: a novel mechanism of intestinal fibrosis

In addition to mesenchymal cells, endothelial cells may contribute to fibrosis through the process of endothelial-to-mesenchymal transition (EndoMT). We investigated whether human intestinal microvascular endothelial cells (HIMEC) undergo EndoMT and contribute to fibrosis in human and experimental inflammatory bowel disease (IBD). HIMEC were exposed to TGF-β1, IL-1β, and TNF-α or supernatants of lamina propria mononuclear cells (LPMC) and evaluated for morphological, phenotypic, and functional changes compatible with EndoMT. Genomic analysis was used to identify transcription factors involved in the transformation process. Evidence of in situ and in vivo EndoMT was sought in inflamed human and murine intestine. The combination of TGF-β1, IL-1β and TNF-α, or activated LPMC supernatants induced morphological and phenotypic changes consistent with EndoMT with a dominant effect by IL-1. These changes persisted after removal of the inducing agents and were accompanied by functional loss of acetylated LDL-uptake and migratory capacity, and acquisition of de novo collagen synthesis capacity. Sp1 appeared to be the main transcriptional regulator of EndoMT. EndoMT was detected in microvessels of inflammatory bowel disease (IBD) mucosa and experimental colonic fibrosis of Tie2-green fluorescent protein (GFP) reporter-expressing mice. In conclusion, chronic inflammation induces transdifferentiation of intestinal mucosal microvascular cells into mesenchymal cells, suggesting that the intestinal microvasculature contributes to IBD-associated fibrosis through the novel process of EndoMT.

Inflammation-induced endothelial-to-mesenchymal transition: a novel mechanism of intestinal fibrosis

In addition to mesenchymal cells, endothelial cells may contribute to fibrosis through the process of endothelial-to-mesenchymal transition (EndoMT). We investigated whether human intestinal microvascular endothelial cells (HIMEC) undergo EndoMT and contribute to fibrosis in human and experimental inflammatory bowel disease (IBD). HIMEC were exposed to TGF-β1, IL-1β, and TNF-α or supernatants of lamina propria mononuclear cells (LPMC) and evaluated for morphological, phenotypic, and functional changes compatible with EndoMT. Genomic analysis was used to identify transcription factors involved in the transformation process. Evidence of in situ and in vivo EndoMT was sought in inflamed human and murine intestine. The combination of TGF-β1, IL-1β and TNF-α, or activated LPMC supernatants induced morphological and phenotypic changes consistent with EndoMT with a dominant effect by IL-1. These changes persisted after removal of the inducing agents and were accompanied by functional loss of acetylated LDL-uptake and migratory capacity, and acquisition of de novo collagen synthesis capacity. Sp1 appeared to be the main transcriptional regulator of EndoMT. EndoMT was detected in microvessels of inflammatory bowel disease (IBD) mucosa and experimental colonic fibrosis of Tie2-green fluorescent protein (GFP) reporter-expressing mice. In conclusion, chronic inflammation induces transdifferentiation of intestinal mucosal microvascular cells into mesenchymal cells, suggesting that the intestinal microvasculature contributes to IBD-associated fibrosis through the novel process of EndoMT.

Isolation of human intestinal mucosal mononuclear cells

The aim of this procedure is to obtain large numbers of isolated, viable, and functional mononuclear cells that are representative of the lymphoid population present in the mucosa of the human gastrointestinal tract under physiological and pathological conditions. The basic protocol is based on the use of surgically resected small and large bowel specimens, and consists of two basic stages: (1) a combination of chemical, enzymatic, and mechanical treatments to dissociate intestinal tissue and free the mononuclear cells from the surrounding interstitial framework; and (2) separation, isolation, and purification of viable mucosal lamina propria mononuclear cells from other cellular and amorphous components. The proportion of viable cells obtained can be increased by including extra separation steps using nylon wool columns or Percoll gradients, as described.

Isolation and subsequent analysis of murine lamina propria mononuclear cells from colonic tissue

Studies on colonic cells in the lamina propria (LP) of mice are important for understanding the cellular and immune responses in the gut, especially in inflammatory bowel diseases (such as morbus crohn and colitis ulcerosa). This protocol details a method to isolate LP cells and characterize freshly isolated cells by quality control experiments to obtain cells that can be used for further investigations. After different steps of digestion of the tissue using collagenase, DNase and dispase, the resulting cells are purified using Percoll gradient. The success of the isolation can be analyzed by cell viability test (Trypan Blue exclusion test) and by flow cytometric analysis to assess apoptosis. Finally, the isolated cells can be used for further investigations like comparative studies of mRNA expression, cell-proliferation assay or protein analysis. This protocol can be completed within 6-7 h.

Chronic nicotine stimulation modulates the immune response of mucosal T cells to Th1-dominant pattern via nAChR by upregulation of Th1-specific transcriptional factor

Inflammatory bowel disease (IBD) consists of Crohn's disease (CD) and ulcerative colitis (UC). The etiology has not been clarified yet, but immune disorder is thought to be involved in the pathogenic physiology. Recently, general consensus has been reached that CD and UC are distinct, especially in respect of the immune response. Interestingly, smoking has diverse effects on CD, Th1-type enteritis, and on UC, Th2-type. However, the mechanisms remain obscure. Therefore, we hypothesized that nicotine altered the distinct immune responses in each form of IBD to affect their pathophysiology. In this study, we first demonstrated by RT-PCR analysis that human lamina propria T (LPT) cells had nicotinic acetylcholine receptor (nAChR), and express alpha7 nAChR subunit universally. In addition, the expression of T-bet mRNA in human LPT cells was significantly upregulated after the culture with 10(-7)M and 10(-5)M nicotine for 9 days, while chronic nicotine stimulation showed negligible effect on the expression of GATA-3 mRNA by real-time PCR. The effect of nicotine was inhibited by mecamylamine (MEC). These results suggested that nicotine could modulate the immune balance to Th1-dominant via nAChR in the intestine, to improve Th2-type enteritis. This may provide the experimental evidence for the fact that nicotine has a beneficial influence on UC, and exacerbates CD. Furthermore, it is of great interest that nicotine acts oppositely on CD and UC by modulation of the mucosal immune balance via the neurotransmitter receptor.

Angiogenesis as a novel component of inflammatory bowel disease pathogenesis

BACKGROUND & AIMS

Angiogenesis is a critical component of neoplastic and chronic inflammatory disorders, but whether angiogenesis also occurs in inflammatory bowel disease (IBD) has yet to be established. We assessed mucosal vascularization, expression of endothelial alphaVbeta3 integrin, angiogenic factors, and their bioactivity in Crohn's disease (CD) and ulcerative colitis (UC) mucosa.

METHODS

Mucosal endothelium was immunostained for CD31 and factor VIII and quantified by digital morphometry. alphaVbeta3 expression was studied in vivo by confocal microscopy and in vitro by flow cytometric analysis of human intestinal microvascular endothelial cells (HIMECs). Vascular endothelial growth factor (VEGF), interleukin (IL)-8, and bFGF levels were measured in mucosal extracts and cells and angiogenic bioactivity shown by induction of HIMEC migration and the corneal and chorioallantoic membrane angiogenesis assays.

RESULTS

Microvessel density was increased in IBD mucosa. Endothelial alphaVbeta3 was strongly expressed in IBD but only sporadically in normal mucosa and was up-regulated in HIMECs by VEGF, tumor necrosis factor alpha, and bFGF. IBD mucosal extracts induced a significantly higher degree of HIMEC migration than control mucosa, and this response was mostly dependent on IL-8 and less on basic fibroblast growth factor or vascular endothelial growth factor. Compared with normal mucosa, IBD mucosal extracts induced a potent angiogenic response in both the corneal and chorioallantoic membrane assays.

CONCLUSIONS

These results provide morphological, phenotypic and functional evidence of potent angiogenic activity in both CD and UC mucosa, indicating that the local microvasculature undergoes an intense process of inflammation-dependent angiogenesis. Thus, angiogenesis appears to be an integral component of IBD pathogenesis, providing the practical and conceptual framework for anti-angiogenic therapies in IBD.

Intestinal Fibroblast-Derived IL-10 Increases Survival of Mucosal T Cells by Inhibiting Growth Factor Deprivation- and Fas-Mediated Apoptosis

Mucosal T cells are essential to immune tolerance in the intestine, an organ constantly exposed to large amounts of dietary and bacterial Ags. We investigated whether local fibroblasts affect mucosal T cell survival, which is critical for maintenance of immune tolerance. Coculture with autologous fibroblasts significantly increased viability of mucosal T cells by inhibiting IL-2 deprivation- and Fas-mediated apoptosis, an effect that was both contact- and secreted product-dependent. Investigation of anti-apoptotic factors in the fibroblast-conditioned medium (FCM) revealed the presence of IL-10 and PGE2, but not IFN-beta, IL-2, or IL-15. Although recombinant IFN-beta, but not PGE2, effectively prevented T cell apoptosis, neutralizing Ab studies showed that only IL-10 blockade significantly increased T cells apoptosis, whereas neutralizing IFN-beta or IFN-alpha failed to inhibit the anti-apoptotic effect of FCM. To confirm that fibroblast-derived IL-10 was responsible for preserving mucosal T cell viability, IL-10 mRNA was demonstrated in fibroblasts by Southern blotting and RT-PCR. When FCM was submitted to HPLC fractionation, only the peak matching rIL-10 contained the anti-apoptotic activity, and this was eliminated by treatment with an IL-10-neutralizing Ab. Finally, when fibroblasts were transiently transfected with IL-10 antisense oligonucleotides, the conditioned medium lost its T cell anti-apoptotic effect, whereas medium from fibroblasts transfected with IFN-beta antisense oligonucleotides displayed the same anti-apoptotic activity of medium from untransfected fibroblasts. These results indicate that local fibroblast-derived IL-10 is critically involved in the survival of mucosal T cells, underscoring the crucial importance of studying organ-specific cells and products to define the mechanisms of immune homeostasis in specialized tissue microenvironments like the intestinal mucosa.

Signal transducers and activators of transcription 3 signaling pathway: an essential mediator of inflammatory bowel disease and other forms of intestinal inflammation

Crohn's disease (CD) and ulcerative colitis (UC), the two major forms of chronic inflammatory bowel disease (IBD), are characterized by mucosal immune cell activation that is driven by a cytokine imbalance. Several cytokines involved in IBD act through the activation of the signal transducers and activators of transcription (STAT) family. We investigated the activation of STAT3 in the mucosa of CD and UC patients, and evaluated whether this event is specific for IBD patients. Using immunofluorescence and immunoblotting, total and phosphorylated STAT3 levels were assessed in biopsy specimens, isolated lamina propria mononuclear cells, and peripheral blood mononuclear cells from patients with CD, UC, other forms of intestinal inflammation, and control subjects. Immunoblotting revealed phosphorylated STAT3 in mucosal biopsy specimens from patients with CD, UC, celiac disease, and acute self-limited colitis, but not in the normal mucosa of control subjects. In IBD patients, STAT3 activation was confined to actively inflamed areas. Accordingly, activated STAT3 was detected in isolated lamina propria mononuclear cells from inflamed IBD tissues, but not in peripheral blood mononuclear cells from control subjects or IBD patients. Immunofluorescence demonstrated that the sources of activated STAT3 were macrophages and T lymphocytes, but not neutrophils. STAT3 activation also was detected in T cells infiltrating the duodenal mucosa of celiac disease patients. We conclude that STAT3 signaling occurs in both CD and UC, where it is strictly confined to areas of active inflammation and is limited to infiltrating macrophages and T cells. The occurrence of STAT3 signaling in other acute and chronic intestinal inflammatory conditions suggests that, rather than a specific feature of IBD, it represents a fundamental signaling pathway that is shared by multiple forms of gut inflammation.

Stimulation of peripheral blood and intestinal mucosa cells by synthetic CpG oligodeoxynucleotides

The breakdown of tolerance to autologous bacterial flora has been implicated as a major factor contributing to the initiation and perpetuation of chronic inflammation in inflammatory bowel diseases (IBD). To test whether bacterial DNA is at the origin of inflammation in IBD, we have examined the response of lamina propria (LPMC) or peripheral mononuclear cells (PBMC) and purified T cells from IBD patients and control patients to stimulations with a set of oligodeoxynucleotides (ODNs) characterized by the presence or absence of cytosine-guanosine dinucleotides (CpG) and/or 3' poly-guanosine (poly-G) extension. Furthermore we have evaluated the costimulatory activities of these ODNs on T cells activated via CD2 or CD3 pathway. We demonstrated that CpG ODNs induce higher proliferation of LPMC from inflammatory intestinal mucosa compared to healthy mucosa. We confirmed that CpG ODNs do not directly costimulate peripheral blood T cells activated by CD3 pathway. Finally, we revealed that CpG or non-CpG ODNs with 3' poly-G extension inhibit completely CD2 activation of purified PB or LP T-cells whereas only CpG ODNs without poly-G extension enhance proliferation and IFN-gamma production of PB T cells stimulated by CD2 pathway only in presence of NK and NK T cells. Our data suggest that NK T cells may be the primary target of ODNs and play a crucial role in indirect T-cell activation by ODN.

Paradoxical decrease of mitochondrial DNA deletions in epithelial cells of active ulcerative colitis patients

Ulcerative colitis (UC) is a condition characterized by chronic inflammation targeted at the epithelial layer. In addition to being involved in immune phenomena, UC epithelial cells exhibit decreased oxidation of butyrate, downregulation of oxidative pathway regulatory genes, and overexpression of mitochondrial (mt) genes. We investigated whether these events, which translate an altered energy metabolism, are associated with an abnormal pattern of mtDNA deletions. Highly purified colonocytes were isolated from surgically resected control, involved and uninvolved inflammatory bowel disease mucosa. The frequency, type, and number of mtDNA deletions were assessed by PCR amplification, Southern blot analysis, and cloning and sequencing of amplified DNA fragments. The 4977 mtDNA deletion was less frequent in UC than control and Crohn's disease (CD) epithelium, regardless of patient age. Several other deletions were detected, but all were less common in UC than control and CD cells. The frequency, variety, and number of mtDNA deletions were invariably lower in colonocytes isolated from inflamed mucosa than in autologous cells from noninflamed mucosa. In conclusion, in the absence of inflammation, UC colonocytes exhibit an mtDNA deletion pattern similar to that of control cells, indicating a normal response to physiological levels of oxidative stress. In active inflammation, when oxidative stress increases, the frequency, variety, and number of mtDNA deletions decrease. Because comparable abnormalities are absent in active CD, the mtDNA deletion pattern of active UC suggests that colonocytes respond uniquely to inflammation-associated stress in this condition.

CD40-mediated immune-nonimmune cell interactions induce mucosal fibroblast chemokines leading to T-cell transmigration

BACKGROUND AND AIMS

The CD40 pathway is a key mediator of inflammation and autoimmunity. We investigated cell adhesion molecule (CAM) up-regulation and chemokine production by CD40-positive human intestinal fibroblasts (HIF) and microvascular endothelial cells (HIMEC) induced by CD40 ligand (CD40L)-positive T cells and soluble CD40L and their effect on T-cell adhesion and transmigration.

METHODS

Expression of CD40, CD40L, and CAM was assessed by immunohistochemistry, confocal microscopy and flow cytometric analysis, and chemokine production using enzyme-linked immunosorbent assay. Calcein-labeled T cells were used to assay HIF adhesion and Transwell HIMEC transmigration.

RESULTS

Ligation of CD40-positive HIF and HIMEC by CD40L-positive T cells or soluble CD40L induced up-regulation of CAM expression as well as interleukin-8 and RANTES production. The specificity of these responses was shown by inhibition with a CD40L blocking antibody and by CD40 signaling-dependent p38 mitogen-activated protein kinase phosphorylation. On CD40 ligation, HIF increased their T-cell binding capacity and generated chemoattractants able to induce T-cell migration through HIMEC monolayers.

CONCLUSIONS

Activation of the CD40/CD40L system in the gut mucosa may trigger a self-sustaining loop of immune-nonimmune cell interactions leading to an antigen-independent influx of T cells that contributes to chronic inflammation.

Extracellular matrix conditions T cells for adhesion to tissue interstitium

The activation and differentiation of peripheral blood T cells (PBT) are known to correlate with increased surface expression and adhesive capacity of beta(1) integrins, which mediate adhesion to the extracellular matrix (ECM). However, little is known about the regulation of integrin expression, affinity, and avidity on tissue T cells after they are embedded in the interstitial ECM. In this study we show that tissue T cells, freshly isolated from their residence in the interstitial ECM of the intestinal lamina propria, express a distinct subset of functionally active integrins that contribute to enhanced adhesion to purified collagen, fibronectin, and cell-derived ECM when compared with freshly isolated, short term activated, and long term cultured PBT. Furthermore, integrin usage is distinct between circulating and tissue-derived T cells, in that lamina propria T cells prefer to bind to collagen, while PBT lymphoblasts choose fibronectin when presented with a complex, three-dimensional, cell-derived matrix. To identify the extrinsic factors that regulate the conversion from a nonadhesive PBT to highly adhesive tissue T cell, we demonstrate that activation of PBT in the presence of fibronectin or collagen rapidly generates a surface integrin expression profile, an integrin usage pattern, and adhesive capacity mirroring that of a tissue T cell. These results indicate that the tissue ECM microenvironment instructs newly arrived T cells for further interactions with the underlying matrix and thereby imprints them with a signature tissue adhesive phenotype.

Urocortin and corticotropin-releasing factor receptor expression in the human colonic mucosa

Urocortin is a newly identified member of the CRF neuropeptide family. Urocortin has been found to bind with high affinity to CRF receptors. The present study investigated urocortin and CRF receptor expression in human colonic mucosa. Non-pathologic sections of adult colorectal tissues were obtained from patients with colorectal cancer at surgery. Urocortin expression was examined using immunohistochemistry and messenger (m) RNA in situ hybridization. Isolated lamina propria mononuclear cells (LPMC) and epithelial cells were also analyzed by flow cytometry for the characterization of urocortin-positive cells, and by RT-PCR for detection of urocortin, CRF, and CRF receptor mRNA. Urocortin peptide distribution at various stages of human development (n = 35, from 11 weeks of gestation to 6 years of age) was examined by immunohistochemistry using surgical and autopsy specimens. Immunoreactive urocortin and urocortin mRNA were predominantly detected in lamina propria macrophages. Urocortin peptide expression was detected from as early as three months of age, but not before birth or in neonates. Urocortin, CRF receptor type 1 and type 2 alpha mRNA were detected in LPMC. CRF receptor type 2 beta mRNA, a minor isoform in human tissues, was also detected in LPMC, but at lower levels. Urocortin is locally synthesized in lamina propria macrophages and may act on lamina propria inflammatory cells as an autocrine/paracrine regulator of the mucosal immune system. The appearance of urocortin after birth indicates that the exposure to dietary intake and/or luminal bacteria after birth may contribute to the initiation of urocortin expression in human gastrointestinal tract mucosa.

Selective resistance of mucosal T-cell activation to immunosuppression in Crohn's disease

BACKGROUND & AIMS

The inappropriately high state of T-cell activation found in Crohn's disease could be due to failure to respond to inhibitory signals. We tested the hypothesis that Crohn's disease mucosal T-cells are resistant to the immunosuppressive action of interleukin4.

PATIENTS

Patients with Crohn's disease, ulcerative colitis, and other malignant and non-malignant conditions undergoing bowel resection.

METHODS

The effect of interleukin-4 on lamina propria mononuclear cells from Crohn's disease, ulcerative colitis and control mucosa was assessed on various T-cell functions: interleukin-2-induced cytotoxicity, soluble interleukin-2 receptor and interleukin-2 production, and expression of mRNA for interleukin-2R and interferon-gamma.

RESULTS

Cytotoxicity of control and ulcerative colitis cells was markedly decreased by interleukin-4, whereas Crohn's disease cells failed to be inhibited. Addition of interleukin-4 to interleukin-2-stimulated cultures decreased soluble interleukin-2R production significantly less in Crohn's disease and ulcerative colitis than control cells. In the same cultures, residual levels of interleukin-2 were significantly increased in control and ulcerative colitis, but not Crohn's disease cultures. Finally, Crohn's disease cells were significantly more resistant to interleukin-4-mediated inhibition of spontaneous and interleukin-2-induced expression of interleukin-2Ralpha and interferon-gamma mRNA compared to control cells.

CONCLUSIONS

The effector function, receptor expression and cytokine production of Crohn's disease mucosal T-cells are resistant to interleukin4-mediated inhibition. Failure to respond to down-regulatory signals may contribute to persistent T-cell activation and chronicity of inflammation in Crohn's disease.

Regulation of ICAM-1-mediated fibroblast-T cell reciprocal interaction: implications for modulation of gut inflammation

BACKGROUND & AIMS

Immune-nonimmune cell interactions modulate mucosal immunity. We investigated the expression of adhesion molecules by intestinal fibroblasts, the effect of immune cell-derived factor on fibroblast binding of T cells, and the consequences of interfering with adhesion molecule expression on fibroblast-T cell interaction.

METHODS

Expression of fibroblast intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 surface and messenger RNA (mRNA) was measured before and after exposure to immune cell-derived supernatants. Fibroblasts were treated with antibodies to ICAM-1 or VCAM-1, or ICAM-1 antisense oligonucleotide Isis 2302, before a T-cell adhesion assay.

RESULTS

Fibroblast activation by immune cell-derived cytokines enhanced ICAM-1 and VCAM-1 surface expression and mRNA as well as adhesiveness for T cells. Blockade with neutralizing antibodies showed that binding was almost exclusively dependent on ICAM-1. Isis 2302 specifically reduced fibroblast ICAM-1 mRNA and dose-dependently inhibited ICAM-1 surface expression and T-cell binding.

CONCLUSIONS

ICAM-1 is essential for intestinal fibroblast binding of T cells, a phenomenon that is efficiently and specifically disrupted by ICAM-1 antisense oligonucleotides. These observations emphasize the crucial regulatory role of fibroblasts in mucosal immunity and their potential as targets for therapeutic intervention in intestinal inflammation.

Differential lamina propria cell migration via basement membrane pores of inflammatory bowel disease mucosa

BACKGROUND & AIMS

In active inflammatory bowel disease (IBD), the intestinal mucosa is infiltrated by polymorphonuclear cells (PMNs), lymphocytes, and monocytes from the systemic circulation. Using an ex vivo model, we have investigated luminally directed migration of cells out of the lamina propria.

METHODS

Fresh untreated and deepithelialized mucosal samples were studied by electron microscopy. Cells migrating out of the lamina propria were investigated by immunohistochemistry and fluorescence-activated cell sorter analysis.

RESULTS

In intact IBD mucosal samples, tunnels containing cells were prominent in the lamina propria matrix, and PMNs, but not other cell types, were prominent in the epithelium. In deepithelialized mucosal samples, the basement membrane was either destroyed or contained numerous large pores. During culture of deepithelialized mucosal samples, many cells (3.3 [+/-0.8] x 10(5) . g tissue-1 . h-1) migrated out of the lamina propria via basement membrane pores. PMNs and eosinophils were prominent during the first 3 hours of culture, but T cells predominated thereafter. Macrophages also migrated, but B cells were the minority population (<2%) at all times.

CONCLUSIONS

In active IBD mucosa with an intact epithelium, luminally directed migration of lamina propria cells is restricted mainly to PMNs. After loss of the epithelium, other cell types also migrate into the lumen via numerous, large, basement membrane pores.

Proinflammatory cytokines differentially modulate their own expression in human intestinal mucosal mesenchymal cells

BACKGROUND & AIMS

Intestinal homeostasis is coordinated through the response of different cell types, including the interaction of immune with nonimmune cells. This study investigated the effect of immune cell-derived proinflammatory cytokines on mesenchymal cell proliferation and gene product expression.

METHODS

Primary cultures of human mucosal mesenchymal cells were activated with interleukin (IL)-1 beta, IL-6, and tumor necrosis factor alpha (TNF-alpha). Proliferation was measured by thymidine incorporation, messenger RNA (mRNA) expression was assessed by Northern blot analysis, and IL-1 receptor type was identified by reverse-transcription polymerase chain reaction.

RESULTS

Mesenchymal cells dose-dependently proliferated in response to IL-1 beta, IL-6, and TNF-alpha. Each cytokine differentially induced mRNA expression in a dose-dependent and selective fashion: IL-1 beta was the most potent inducer, TNF-alpha was weaker, and IL-6 induced little or no mRNA; in contrast, IL-6 mRNA was the most abundantly induced, followed by IL-1 beta mRNA, whereas TNF-alpha mRNA was weakly and infrequently expressed. The IL-1 receptor antagonist inhibited cytokine mRNA expression, and mesenchymal cells expressed the type II, but not the type I, IL-1 receptor.

CONCLUSIONS

The ability of intestinal mesenchymal cells to express proinflammatory gene products implicates them as regulators of local immune cells through immune-nonimmune interactions. Thus, mesenchymal cells should be considered as active regulators of intestinal immunity under normal and inflammatory conditions.

Crohn's disease and ulcerative colitis mucosal T cells are stimulated by intestinal epithelial cells: implications for immunosuppressive therapy

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases, and their pathogenesis is attributed, in part, to alterations of the mucosal immune system. This study was designed to define the possible contribution of epithelial cells to the activation of lamina propria T lymphocytes (LPTs) in CD and UC.

METHODS

LPTs isolated from CD, UC, and control surgical specimens were cocultured with freshly isolated allogeneic or autologous epithelial cells or epithelial cell lines. Resulting T-cell proliferation was evaluated by tritiated thymidine incorporation on day 5.

RESULTS

When intestinal epithelial cells were used to stimulate mucosal T-cell proliferation, CD and UC LPTs were less responsive than control LPTs (p < 0.05 and p < 0.03, respectively). This difference between inflamed and control T cells was consistently observed by using a variety of different intestinal epithelial cell types.

CONCLUSIONS

CD and UC mucosal T cells are hyporesponsive to activation by intestinal epithelial cells when compared with control LPTs. Elucidating the mechanism underlying the differential activation of CD and UC LPTs may help to better understand the immunopathogenesis of these conditions.

Regulation by prostaglandin E2 of interleukin release by T lymphocytes in mucosa

Regulation of immune cell activation in lymphocyte-bearing human tissues is a pivotal host function, and metabolites of arachidonic acid (prostaglandin E2 in particular) have been reported to serve this function at non-mucosal sites. However, it is unknown whether prostaglandin E2 is immunoregulatory for the large lymphocyte population in the lamina propria of intestine; whether low (nM) concentrations of prostaglandin E2 modulate immune responses occurring there; and whether adjacent inflammation per se abrogates prostaglandin E2's regulatory effects. To address these issues, intestine-derived lymphocytes and T hybridoma cells were assessed, T cell activation was monitored by release of independently quantitated lymphokines, and dose-response studies were performed over an 8-log prostaglandin E2 concentration range. IL-3 release by normal intestinal lamina propria mononuclear cells was reduced (up to 78%) in a dose-dependent manner by prostaglandin E2, when present in as low a concentration as 10(-10) M. PGE2 also inhibited (by > or = 60%) mucosal T lymphocytes' ability to destabilize the barrier function of human epithelial monolayers. Further, with an intestine-derived T lymphocyte hybridoma cell line, a prostaglandin E2 dose-dependent reduction in IL-3 and IL-2 (90 and 95%, respectively) was found; this was true for both mitogen- and antigen-driven T cell lymphokine release. Concomitant [3H] thymidine uptake studies suggested this was not due to a prostaglandin E2-induced reduction in T cell proliferation or viability. In contrast, cells from chronically inflamed intestinal mucosa were substantially less sensitive to prostaglandin E2, e.g., high concentrations (10(-6) M) of prostaglandin E2 inhibited IL-3 release by only 41%. We conclude that prostaglandin E2 in nM concentrations is an important modulator of cytokine release from T lymphocytes derived from the gastrointestinal tract, and it may play a central role in regulation of lamina propria immunocyte populations residing there.

Adequacy of mucosal biopsies for evaluation of intestinal cytokine-specific mRNA. Comparative study of RT-PCR in biopsies and isolated cells from normal and inflamed intestine

Endoscopic biopsies are being increasingly utilized to investigate cytokine profiles in normal and diseased intestine. To evaluate the adequacy of mucosal biopsies as a source of cytokine-specific mRNA, we measured their content of interleukin-1 beta (IL-1 beta) and interleukin-2 (IL-2) mRNA by reverse transcription-polymerase chain reaction and compared it to that of autologous lamina propria mononuclear cells in control and inflammatory bowel disease-involved specimens. High-quality total RNA was recovered more consistently from cell isolates than from biopsies. Interleukin-1 beta mRNA was reliably detected in both cell and biopsy samples, whereas IL-2 mRNA was measurable in all lamina propria cells but not always in biopsies. Compared to controls, levels of IL-1 beta were significantly elevated in Crohn's disease and ulcerative colitis cells and biopsies, and a weak but significant correlation existed between values derived from the two sources. In contrast, only ulcerative colitis cell isolates but not biopsies contained significantly reduced concentrations of IL-2 mRNA compared to those of control and Crohn's disease samples, and no correlation was found between cell and biopsy contents. Widely different levels of cytokine-specific mRNA were present in closely adjacent biopsies, particularly for IL-2. These results suggest that mucosal biopsies are suitable to assess some but not all cytokine-specific mRNA due to variation in RNA recovery, intrinsic level of cytokine gene expression, and substantial variability of cytokine transcripts.

Immunological studies on Crohn's disease. X. Conclusion: a new tentative hypothesis

Although much progress has been made in understanding the pathogenesis of Crohn's disease, the precise etiology of Crohn's disease still remains unknown. In our serial studies on Crohn's disease, we found a decrease in NK and ADCC activities as well as a decrease in the phagocytic activity by monocytes, whereas an increased superoxide production activity by monocytes was evident. On the other hand, the characterization of lymphocyte subpopulations has demonstrated no abnormalities. According to these findings, we would like to propose a new tentative hypothesis for the pathogenesis of Crohn's disease. It has been suggested that impaired killing system activities, such as phagocytic activity as well as NK and ADCC activities, are primarily responsible for the promotion and perpetuation of chronic inflammation and ulceration. When our attention is directed to the most common target substances of these protective mechanisms, viral antigens appear as the most likely causative organism. Therefore, a lot of attention has been focused on viral infection as a causative factor. Furthermore, based on this hypothesis, strategies for effective treatment of this disease are also discussed.

Analysis of T-lymphocyte subpopulations in inflammatory bowel diseases by three-color flow cytometry

In order to better define changes in the relative proportion of peripheral blood T-lymphocyte subpopulations in patients with inflammatory diseases of the bowel, we performed simultaneous three-color fluorescence-activated cytometric (FACS) analysis using fluorophore-conjugated monoclonal antibodies with specificity for CD4, CD8, Leu 8, and CD45RA on 22 normal control subjects, 28 patients with Crohn's disease (CD), 15 patients with ulcerative colitis (UC), and 11 patients with intestinal inflammation secondary to etiologies other than inflammatory bowel disease (NIBD). This staining combination allowed enumeration of distinct T-cell subpopulations as follows: virgin CD4+, recall antigen helper T cells, nonspecific B-cell helper T cell, virgin CD8+, cytotoxic effector and suppressor effector and recall antigen cytotoxic T cells based on a synthesis of published functional analyses. No differences in the proportion of CD4+ or CD8+ cells or in the CD4+/CD8+ ratios were evident when UC and NIBD patients were compared to normal subjects. A significant reduction in the proportion of CD4+ cells and an increase in CD8+ cells was observed, however, in the CD group. When two-color analysis was performed, several significant differences in the proportions of circulating lymphocytes were seen. Specifically, these included significant increases in the number of CD4+, Leu 8- (P < 0.01) cells in all disease groups and an increase in CD4+, CD45RA+ cells in the NIBD group. Conversely, significant decreases in the proportions of CD8+, Leu 8+ (P < 0.01) cells were evident in the Crohn's disease group.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous cytotoxicity of intestinal intraepithelial lymphocytes: clues to the mechanism

Human intestinal intraepithelial lymphocytes (IEL) demonstrate target cell-restricted spontaneous cytotoxic (SC) activity that is due to CD2+CD3+CD8+CD16-CD56- effector cells; they kill epithelial cell (EC) tumours (such as DLD-1 colon cancer cells), but not natural killer (NK)-sensitive K-562 cells. The present study shows that the measured levels of SC activities by IEL correlated with those of autologous lamina propria lymphocytes (LPL), but not with those of peripheral blood lymphocytes (PBL). Also, the susceptibilities of DLD-1 cell clones to lysis by IEL and PBL effector cells did not correlate, suggesting different mechanisms of lysis. Antibody blocking experiments showed that the main surface molecules involved in lysis depended on the effector cell type: alpha E beta 7 (HML-1) on IEL and CD16 on PBL. No antibody-dependent cell-mediated cytotoxicity (ADCC) was demonstrated by IEL, even after stimulation with interferon-gamma (IFN-gamma). Few IEL expressed Fc receptors for IgG. This study describes further differences between the SC activities of IEL and PBL.

Quantitative measurement of human T-cell receptor V beta subfamilies by reverse transcription-polymerase chain reaction using synthetic internal mRNA standards

Quantitative determination of T-cell receptor (TCR) V beta expression is necessary to define the changes in TCR-V beta subfamily expression that occur during T-cell maturation and selection and to detect alterations of the TCR-V beta repertoire that may be associated with human diseases. Here we describe and validate a quantitative reverse transcription-polymerase chain reaction (RT-PCR) technique to determine human TCR-V beta subfamily mRNA levels (as well as other mRNA species), based on the use of synthetic poly(A) mRNA internal standards that are coprocessed with native (sample) mRNA transcripts. The technique allows simultaneous reverse transcription of sample and standard mRNA and thus obviates errors arising during reverse transcription. In addition, the technique allows coamplification of several concentrations of standard mRNA (cDNA) with sample mRNA (cDNA) under conditions in which these mRNAs amplify with equal efficiency; thus, it avoids errors resulting from saturation of competition effects. Finally, the technique is sensitive to lower than 1.5-fold differences in input mRNA. To apply the technique, we also describe methods for the generation of poly(A) mRNA internal standards that can be used to quantitate TCR-V beta 2/6/7 and TCR-C beta mRNA.

Clonal expansion of lymphocytes from oral lichen planus lesions

Lymphocytes were extracted from 11 biopsy specimens of oral lichen planus (OLP) by collagenase digestion, and cell lines were expanded with repetitive cycles of stimulation (with phytohaemagglutinin) and rest in media supplemented with interleukin 2. Four OLP lines contained a majority of CD3+CD4-CD8+ cells, in six lines the CD4:CD8 ratio was between 1 and 2, and in one line the CD4:CD8 ratio was 5:1. Limiting dilution of nine lines at 0.3 and 1.0 cells/well resulted in viable wells (putative clones) with plating efficiencies ranging from 0.0 to 18.1 percent and 0.0 to 22.2 percent respectively. The majority of clones were CD3+CD4-CD8+alpha beta+gamma delta-, although three clones were CD3+CD4+CD8-alpha beta+gamma delta- and one clone was CD3+CD4-CD8- and expressed the gamma delta T cell receptor. T cell clones derived from lymphocytes extracted from OLP lesions may be generated and maintained in culture providing opportunity for their further phenotypic and functional characterisation. This strategy may facilitate the identification of a putative oral lichen planus-specific antigen and indicate the frequency of lichen planus-specific T cells within lesions of OLP.

Localization of intestinal interleukin 1 activity and protein and gene expression to lamina propria cells

BACKGROUND

Interleukin 1 (IL-1) is a key mediator of bowel inflammation, but there is limited knowledge about the amount and site of production of this cytokine in the gastrointestinal tract under physiological or pathological conditions.

METHODS

Epithelial and lamina propria mononuclear cells were isolated from control, and Crohn's disease- and ulcerative colitis-involved mucosa to investigate the capacity of these cells to generate IL-1 bioactivity, IL-1 alpha and IL-1 beta immunoreactivity, and gene expression.

RESULTS

Control lamina propria mononuclear cells produced substantial amounts of IL-1 alpha and IL-1 beta, which increased dramatically when inflammatory bowel disease cells were used. Epithelial cells from control, Crohn's disease, and ulcerative colitis intestine displayed no IL-1 bioactivity or immunoreactivity. Lamina propria mononuclear cells contained moderate to large quantities of IL-1 alpha and IL-1 beta messenger RNA (mRNA), respectively, whereas epithelial cells had none. The absence of IL-1 transcripts in epithelial cells was selective, because mRNA for HLA-DR antigens was present in control and inflammatory bowel disease cells.

CONCLUSIONS

In normal and inflamed human intestine there is a distinct compartmentalization of IL-1, as mononuclear but not epithelial cells generate this cytokine. The high levels of IL-1 in inflammatory bowel disease may explain several of its local and systemic manifestations, and blockade by specific antagonists could have important therapeutic effects.

Immune activation genes in inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease is associated with enhanced activation of T cells, but the genes responsible for this state are not well characterized.

METHODS

T-cell activation genes were studied in peripheral blood and intestinal mucosal mononuclear cells of control, Crohn's disease, and ulcerative colitis patients.

RESULTS

In all groups the expression of interleukin-2 (IL-2), IL-2 receptor alpha (IL-2R alpha), and IL-2R beta messenger RNA (mRNA) was significantly higher in intestinal than circulating cells, and it correlated well with protein levels. Both IL-2R alpha and IL-2R beta mRNA were abundant in mucosal cells, suggesting that a substantial number of them displays high affinity IL-2R. This would explain why intestinal cells proliferate more, express more IL-2 transcripts, and secrete more IL-2 than peripheral cells. Inflammatory bowel disease cells produced similar or higher IL-2R alpha and IL-2R beta mRNA than controls but generated significantly lower IL-2 mRNA. Thus, the reported defect of IL-2 activity in Crohn's disease and ulcerative colitis is probably related to decreased IL-2 transcription. Crohn's disease intestinal cells had the highest expression of IL-2R gene products. This provides a mechanism for their increased response to IL-2 and supports claims that elevated soluble IL-2R alpha serum levels reflect gut T-cell hyperactivity in this disease.

CONCLUSIONS

These findings underscore the importance of T cells in mucosal immunity and indicate that abnormal T-cell activation is intimately associated to the pathogenesis of inflammatory bowel disease.

Normal inflammatory bowel disease mucosa conceals alterations in natural killer cell activity

Non-major histocompatibility complex-restricted cytotoxicity or natural killer (NK) activity could be detected in all intestinal lamina propria mononuclear cell preparations of histologically normal mucosa from 57 patients with gastrointestinal disease. Similar levels of NK activity were detected among the different disease groups. Within the inflammatory bowel disease patient group, however, Crohn's disease patients showed a threefold higher level of NK activity than detected in ulcerative colitis patients. Cytotoxicity levels in Crohn's disease patients were also higher than in the control carcinoma patients, whereas ulcerative colitis patients had considerably lower cytotoxicity levels than the carcinoma patients. Thus, unaffected normal inflammatory bowel disease mucosa conceals alterations in NK activity which might occur before the inflammation. The colon adenocarcinoma cell line Caco-2 was found to be a representative target for detecting individual differences in NK activity of lamina propria mononuclear cells compared with standard K-562 targets. The latter can be of relevance when studying mucosal immunoregulatory mechanisms in intestinal disease.

Soluble interleukin 2 and CD8 and CD4 receptors in inflammatory bowel disease

Serum levels of soluble interleukin 2 receptor (sIL-2R) have been proposed as a clinical marker of inflammatory bowel disease. The source of sIL-2R in patients with Crohn's disease and ulcerative colitis is unknown, and other soluble receptors have not been investigated. In the present study, sIL-2R and soluble CD8 and CD4 levels were measured in plasma and culture supernatants of peripheral blood and intestinal mucosal mononuclear cells from patients with inflammatory bowel disease, surgical controls, and healthy subjects. Level of plasma sIL-2R was significantly higher in patients with Crohn's disease and ulcerative colitis than in healthy volunteers. Intestinal cells always produced more sIL-2R than peripheral cells. Spontaneous sIL-2R production by mucosal cells was significantly elevated in Crohn's disease but not in ulcerative colitis supernatants compared with levels of surgical controls. Soluble CD8 and CD4 were poor indicators of systemic or mucosal immunity. A positive correlation was found between plasma sIL-2R and spontaneous production by intestinal cells of patients with Crohn's disease and surgical control patients, whereas ulcerative colitis plasma sIL-2R correlated with spontaneous production by peripheral cells. The association of plasma or spontaneous sIL-2R levels with the degree of intestinal inflammation was weak, and there was a wide overlap with control values. Therefore, caution should be used before considering sIL-2R an accurate marker of inflammatory bowel disease activity.

Antigen induced suppression in peripheral blood and lamina propria mononuclear cells in inflammatory bowel disease

Using an autologous system, suppressor cell function to a range of mycobacterial antigens and Kunin antigen of peripheral blood mononuclear cells and lamina propria lymphocytes has been investigated in normal subjects and patients with inflammatory bowel disease. In the peripheral blood there was reduced antigen induced suppression in patients with Crohn's disease in remission to Mycobacterium paratuberculosis, purified protein derivative (PPD), M fortuitum, and Kunin antigens (p less than 0.05). In patients with ulcerative colitis in remission there was reduced antigen induced suppression in the peripheral blood to Kunin antigen (p less than 0.001), M avium (p less than 0.01), M nonchromogenecin, and M fortuitum (p less than 0.05). The phenomenon of antigen induced suppression was largely CD8 dependent, as depleting CD8+ cells reduced the effect and the concentration of soluble CD8 in the culture supernatant was directly related to the suppressor index (r = 0.25, p less than 0.05). These results are likely to be a true reflection of the cell mediated response to antigen as patients with a positive Mantoux skin test have a significantly higher suppressor index to PPD than Mantoux negative subjects (p less than 0.05). These findings may have significance in the aetiopathogenesis of inflammatory bowel disease. However, a similar effect could not be shown in the lamina propria lymphocytes of patients having colectomy for active disease.

Enhanced mucosal cytokine production in inflammatory bowel disease

Proliferation, maturation, chemotaxis, and activation of neutrophils and monocytes are mediated largely by cytokines, including colony-stimulating factors and lymphokines. Cytokines produced in the intestinal mucosa contribute to the increased migration of neutrophils and monocytes into the lesion of inflammatory bowel disease and to the activation of these inflammatory cells. Lamina propria mononuclear cells isolated from colon tissue from 14 patients with inflammatory bowel disease (IBD) and from histologically normal controls were studied. Cells from IBD-affected tissue produced significantly more colony-stimulating factor activity (1402 +/- 252 U) per 2 x 10(6) cells than those from normal mucosa (362 +/- 85 U), mainly because of the increased production of granulocyte colony-stimulating factor and interleukin 1. This was accompanied by increases in the amount of specific messenger RNA for these two cytokines in lamina propria mononuclear cells from mucosa of patients with Crohn's disease (CD) compared with normal controls. By contrast, there was a substantial reduction in interleukin 3 production in CD and in ulcerative colitis lamina propria mononuclear cells, and this was reflected in significantly reduced expression of interleukin 3 messenger RNA in CD cells. Of the agents used in the therapy of IBD, hydrocortisone and 5-aminosalicylic acid, but not cyclosporin A, markedly suppressed in vitro production of cytokines by lamina propria mononuclear cells, suggesting that their therapeutic efficacy in vivo may be due in part to down-regulation of cytokine production in the inflamed mucosa.

The CD56 adhesion molecule is the major determinant for detecting non-major histocompatibility complex-restricted cytotoxic mononuclear cells from the intestinal lamina propria

In this study, specific antibodies against natural killer (NK) cell surface markers identify these cells to be commonly present in normal intestinal mucosa of inflammatory bowel disease (IBD) and carcinoma patients. Cells expressing the CD56 adhesion molecule were found to be far more abundant than CD16+ cells. Functional studies revealed that cells mediating non-major histocompatibility complex-restricted cytotoxicity (NK activity) in the lamina propria express the CD56 surface antigen, whereas only a minority of this activity resides in the population with CD16 expression. This is in contrast with peripheral blood NK cells, which were found to be almost exclusively both CD16+ and CD56+. Moreover, in the lamina propria of the intestine we found CD3+ T lymphocytes not to be involved in spontaneous cell-mediated killing of tumor cells. Considerably higher numbers of cells with the CD16 or CD56 surface markers were found to be present in normal mucosa of IBD patients compared with normal mucosa of carcinoma patients, which was also reflected in higher levels of cytotoxicity detected in lamina propria mononuclear cell preparations from normal IBD mucosa. Because of the disease-related localization of the mucosa studied from both patient groups, i.e. ileum vs. colon, the observed differences may be related to tissue characteristics. Within the IBD group, relatively high levels of cytotoxicity were found in cell preparations from normal mucosa of Crohn's disease patients compared with ulcerative colitis patients, which might support the current concept that Crohn's disease affects the whole of the gastrointestinal tract.

Loss of interleukin-2-producing intestinal CD4+ T cells in inflammatory bowel disease

Interleukin-2 activity of intestinal lamina propria mononuclear cells is decreased in Crohn's disease and ulcerative colitis patients compared with control patients with noninflammatory bowel disease. Factors that might be responsible for this phenomenon were investigated. Most interleukin-2 activity was produced by helper (CD4+) T cells. These were present in comparable numbers in both inflammatory bowel disease and control cultures, but the frequency of interleukin-2-producing cells was significantly (3-4 times) lower among Crohn's disease and ulcerative colitis than control cells. In agreement with this finding, levels of interleukin-2 messenger RNA were substantially decreased in both forms of inflammatory bowel disease compared with controls. Mucosal CD8+ T cells and plastic-adherent cells were unable to suppress interleukin-2 activity by autologous or allogeneic CD4+ T cells. The rate of interleukin-2 absorption was similar for inflammatory bowel disease and control cells. Induction of interleukin-2 by different stimuli (phorbol ester, phytohemagglutinin, or anti-CD3 monoclonal antibody) before or after incubation under basal conditions ("resting") failed to normalize the capacity to generate interleukin-2 by Crohn's disease and ulcerative colitis cells. Prostanoids (prostaglandin E2 and 6-keto-prostaglandin F1 alpha) were produced in large amounts in cultures of inflammatory bowel disease cells, but inhibition by indomethacin failed to restore interleukin-2 activity to control levels. Finally, supernatants from Crohn's disease and ulcerative colitis cell cultures failed to suppress interleukin-2 production by control CD4+ T cells. Our results show that the low interleukin-2 activity detected in inflammatory bowel disease mucosa is not caused by activated suppressor cells, excessive lymphokine utilization or immune stimulation, a defective response to activation signals, or production of inhibitory substances. Rather, the low interleukin-2 activity appears to be related to a loss of interleukin-2-producing mucosal CD4+ T cells. It is concluded that abnormalities of intestinal CD4+ T-cell function are associated with the immunopathogenesis of Crohn's disease and ulcerative colitis.

Epidermal growth factor regulation of DNA synthesis in human colonic lamina propria lymphocytes

Epidermal growth factor (EGF) is a potent growth factor for many tissues including the gastrointestinal tract. EGF is present in the gut lumen and is absorbed through the mucosa in the developing animals. In addition, EGF has been found to alter the immune system. In this study, we investigated the in vitro effect of EGF on normal colonic lamina propria lymphocyte DNA synthesis and ornithine decarboxylase activity. Human colonic lamina propria lymphocytes were isolated by collagenase-EDTA digestion. The effect of EGF on Con A-stimulated lymphocyte thymidine incorporation was tested. We observed that EGF suppressed DNA synthesis and ornithine decarboxylase (ODC) activity in lamina propria lymphocytes. EGF did not alter the time course of thymidine incorporation into LPL stimulated by the combination of phorbol 12,13-dibutyrate (PDB) and ionomycin. Our data suggest that (1) EGF suppresses DNA synthesis in human colonic lamina propria lymphocytes as well as ODC activity and (2) this inhibition may be mediated through protein kinase C or calcium flux. We postulate that EGF may have a role in modulating the human gut immune system.

The expression and regulation of class II antigens in normal and inflammatory bowel disease peripheral blood monocytes and intestinal epithelium

Elevated constitutive expression of major histocompatibility (MHC) class II antigens occurs in the enterocytes of patients with IBD. It has been suggested that this aberrant expression of class II molecules may play a role in the pathogenesis of IBD. We examined two possible reasons for such a finding. 1) Heightened sensitivity of IBD enterocytes to endogenous gamma interferon (gamma IFN) and 2) enhanced endogenous secretion of gamma interferon by intestinal cells in close proximity to the enterocytes (lamina propria lymphocytes). Constitutive and gamma interferon stimulated HLA-DR and DP density on intestinal epithelial cells (IEC) and peripheral blood monocytes (PBM) from UC patients (IEC n = 13; PBM n = 20), CD patients (IEC n = 14; PBM n = 18) and non-IBD controls (IEC n = 12; PBM n = 20) were measured via flow cytometry (mean channel fluorescence). gamma IFN production by PHA stimulated and unstimulated lamina propria lymphocyte (LPL) cultures of UC patients (n = 11) CD patients (n = 8) and non-IBD controls (n = 11) was measured using a vesicular stomatitis virus/WISH cell bioassay. We found significantly greater gamma IFN secretion by IBD-derived PHA stimulated LPL than from non-IBD stimulated controls (CD = 39.4 +/- 12.4u; UC41.5 +/- 6.8u; NL = 22.4 +/- 8.3u, p less than 0.05) while gamma IFN induced HLA-DR and DP upregulation was no greater in IBD-derived IEC and PBM than in non-IBD controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistological studies of surface antigen on colonic lymphoid cells in normal and inflamed mucosa. Comparison of follicular and lamina propria lymphocytes

Mucosal samples from 16 patients with idiopathic inflammatory bowel disease were examined immunohistologically using several monoclonal antibody combinations, and the results were compared with those obtained in other colonic inflammatory disorders and in normal mucosa. Within and around lymphoid follicles, most T cells expressed the restricted common leucocyte antigen (CD45R, displayed by unprimed T cells). Conversely, most lamina propria T cells were negative for CD45R but stained positively with UCHL1 (a monoclonal antibody recognizing an antigen displayed by primed T lymphocytes). The proportions of T-lymphocyte subpopulations in normal and inflamed mucosa were similar, except that CD6-negative, CD7-positive cells were significantly more frequent in inflammatory bowel disease. A characteristic feature of ulcerative colitis and Crohn's colitis was marked infiltration by CD45R+ lymphoid cells that did not coexpress T- or B-cell surface antigens; some stained positively with plasma cell reagents, suggesting that they may be activated B cells. The observations in the colitis sections are consistent with the interpretation that T and B cells alter their surface antigen expression as they emerge from follicles and enter the inflamed lamina propria.

Immune events associated with inflammatory bowel disease

Immunologic abnormalities have been implicated in the etiology of inflammatory bowel disease (IBD). Defects of systemic immunity and of local (intestinal) immunity have been studied. The numbers of T and B lymphocytes and their characteristics seem to vary with the disease, but no cause-and-effect relationship has been established. The presence of anticolon antibodies in patients with ulcerative colitis suggests that these antibodies could be involved in IBD, but they have also been found in other conditions. In the peripheral blood, abnormalities of cell-mediated immunity are inconsistent and suggest that they are not fundamental defects of the disease. The hypothesis that the inflammatory process is a result of immune-mediated intestinal tissue damage is being extensively studied. The high familial incidence of the disease suggests a role of histocompatibility locus antigens, but no reproducible association can be established. In vivo and in vitro studies of mucosal mononuclear cells have revealed abnormalities of immunoglobulin production, some types of cytotoxicity against gut-derived antigens, and altered lymphokine production associated with the disease. Further studies of the intestinal immune system would seem to be the most fruitful line of research.

Intestinal immune reactivity to interleukin 2 differs among Crohn's disease, ulcerative colitis, and controls

When stimulated by the lymphokine interleukin 2, human intestinal mucosal mononuclear cells mediate lymphokine-activated killer cell activity. When supplied with optimal doses of exogenous interleukin 2, lamina propria mononuclear cells isolated from inflammatory bowel disease and control tissue display comparable levels of cytotoxicity in vitro. However, cultures of Crohn's disease- and ulcerative colitis-derived cells contain significantly decreased interleukin 2 activity, suggesting that in vivo the availability of interleukin 2 may be limited, perhaps resulting in impaired cytotoxic function. To test this hypothesis, lamina propria mononuclear cells from inflammatory bowel disease and control patients were stimulated to produce endogenous interleukin 2, which was then used to induce autologous lymphokine-activated killer cells. When tested against K562 and Daudi target cells, Crohn's disease cells, despite producing only one-third of the amount of interleukin 2 generated by control cells, exhibited comparable levels of cytotoxicity. In contrast, ulcerative colitis cells produced substantially less interleukin 2 and exhibited remarkably low lymphokine-activated killer cell activity. When the same cells were supplied with an amount of human recombinant interleukin 2 equivalent to the average titer found in control cultures, similar results were obtained, and Crohn's disease cells even showed a significantly greater cytolytic activity than controls. These results suggest that the observed differences in lymphokine-activated killer cell activity cannot be attributed to the level of interleukin 2 alone, and that response to this lymphokine is different among Crohn's disease, ulcerative colitis, and control intestine. In Crohn's disease, there is either an increased number of interleukin 2-responsive cells or an exacerbated reactivity to interleukin 2. In ulcerative colitis, a loss of interleukin 2-responsive cells, a hyporesponsiveness to interleukin 2, or both might be present. In conclusion, this study demonstrates that reactivity to interleukin 2 distinguishes inflammatory bowel disease from control intestinal mononuclear cells, and, under appropriate experimental conditions, it can be used to uncover abnormalities of intestinal immunity.

Lymphokines and the intestinal immune response. Role in inflammatory bowel disease

The study of production of and response to various soluble mediators by gut-derived mucosal mononuclear cells has contributed significantly to a better understanding of the regulation of the intestinal immune system. So far, a number of factors have been investigated in some detail or in a preliminary fashion: interleukin 1, interleukin 2, interleukin 4, interferon gamma and colony-stimulatory factors. Their level of activity, and their effect on the intestinal mucosal immune system are discussed, particularly in regard to their potential role in the pathogenesis of inflammatory bowel disease.

Expression of HLA-DR antigens in inflammatory bowel disease mucosa: role of intestinal lamina propria mononuclear cell-derived interferon gamma

The expression of HLA-DR antigens on the surface of immune cells is crucial for appropriate antigen presentation and a normal immune response. In the intestinal mucosa involved by Crohn's disease and ulcerative colitis the expression of HLA-DR antigens is increased in both immune and nonimmune cells, a phenomenon probably mediated by soluble factors, such as interferon gamma, produced by locally activated mononuclear cells. This study investigated the production of interferon gamma by inflammatory bowel disease and control intestinal lamina propria mononuclear cells, and the ability of this endogenously produced lymphokine to induce expression of HLA-DR antigens on the monocytic cell lines U937 and ML3. After in vitro stimulation with interleukin 2 or phytohemagglutinin, but not spontaneously, lamina propria mononuclear cells produced variable amounts of interferon gamma, and their culture supernatants could induce de novo expression of HLA-DR antigens on the monocytic indicator cells. When the mononuclear cells were derived from inflammatory bowel disease mucosa, both the amount of interferon gamma present in the supernatants and the number of HLA-DR-positive cells induced by these supernatants were decreased as compared to controls. These results suggest that, in inflammatory bowel disease, interferon gamma may not be the only mediator of HLA-DR induction in the gut and that other soluble factors or agents, alone or interacting with interferon gamma, may also be responsible for this event, resulting in the enhanced HLA-DR antigen expression observed in the inflamed intestinal mucosa.

(2'-5')Oligoadenylate synthetase activity in intestinal mononuclear and epithelial cells of inflammatory bowel disease patients

The activity of (2'-5')oligoadenylate synthetase, an enzyme induced by and mediating the antiviral action of interferon, was measured in extracts of intestinal mononuclear and epithelial cells isolated from patients with Crohn's disease, ulcerative colitis, and a control group. No significant differences were detected among (2'-5')oligoadenylate synthetase activities of lamina propria mononuclear cells derived from inflammatory bowel disease-involved and histologically normal control mucosa. Similarly, epithelial cells from inflammatory bowel disease and control patients expressed comparable levels of the enzyme, but these were significantly higher (p less than 0.01) than those found in autologous mononuclear cells. These results indicate that interferon is locally produced along the human intestinal mucosa under normal and inflammatory conditions. While this study supports the contention that induction of an antiviral state does not play a significant role in the pathogenesis of inflammatory bowel disease, it does not exclude the activation of the interferon system for other immunologic functions.

Modulation of intestinal immune reactivity by interleukin 2. Phenotypic and functional analysis of lymphokine-activated killer cells from human intestinal mucosa

There is evidence indicating that interleukin 2 may be important in the regulation of intestinal immunity, as suggested by its capacity to induce nonspecific cytotoxic (lymphokine-activated killer) activity from human intestinal mucosal mononuclear cells. The present study was designed to further explore the phenotypic and functional changes induced by interleukin 2 on intestinal lymphocytes derived from inflammatory bowel disease and control tissues. Immunohistology of intestinal mucosa demonstrated few cells bearing the activation antigen recognized by anti-Tac (anti-interleukin 2 receptor) monoclonal antibody. However, when isolated lamina proprial mononuclear cells were exposed to interleukin 2 in culture, the number of Tac-positive cells increased dramatically, a phenomenon paralleled by the generation of lymphokine-activated killer cell activity. This cytotoxic function was critically dependent on the continuous availability of interleukin 2, but not on the expression of the Tac antigen, since Tac-negative cells were also cytotoxic. Depletion of natural killer cells, fractionation into T cell-enriched and -depleted cells before and after culturing with interleukin 2, and separation into Tac-positive and -negative cells after interleukin 2 activation failed to eliminate lymphokine-activated killer cell activity, suggesting that this phenomenon is mediated by phenotypically and functionally heterogeneous cell subsets. During the induction of lymphokine-activated killer cells variable amounts of interferon-gamma were produced, but these did not correlate with the degree of cytotoxicity. No differences were observed between the response to interleukin 2 by inflammatory bowel disease and control cells. Therefore, in view of its capacity to induce significant phenotypic and functional changes in different subpopulations of intestinal mucosal mononuclear cells, interleukin 2 should be regarded as an important modulator of intestinal immune reactivity.

Interferon gamma production by human intestinal mucosal mononuclear cells. Decreased levels in inflammatory bowel disease

Immune (gamma) interferon is a substance produced by immunologically activated mononuclear cells. Besides its antiviral activity, interferon gamma has a crucial role in immunoregulation, by acting directly upon lymphocytes and monocytes, and interacting with other soluble mediators of the immune response. Studies of the interferons system in inflammatory bowel disease have been limited, and little information is available on the generation of interferon during immunological events occurring in the human gut. To investigate the capacity of intestinal mucosal mononuclear cells to produce interferon gamma, lamina proprial mononuclear cells, isolated from Crohn's disease, ulcerative colitis, and control patients, were incubated with interleukin 2 or phytohemagglutinin, and the amounts of interferon gamma present in the culture supernatants were measured by a virus cytopathic effect inhibition assay. Under identical stimulatory conditions, culture supernatants of cells derived from actively involved mucosa of inflammatory bowel disease specimens contained two- to fivefold less interferon gamma than those of cells from control tissue. However, the amount of interferon gamma present in supernatants of cells from uninvolved inflammatory bowel disease mucosa was similar to that found in control supernatants. These results indicate that, in patients with active Crohn's disease and ulcerative colitis, mononuclear cells produce decreased amounts of interferon gamma in the intestinal mucosa. The exact significance of these findings is unclear, but because of the importance of interferon gamma in a variety of cell-mediated immune phenomena, its impaired availability might be relevant to the pathogenesis of inflammatory bowel disease.