Immune phenotype of children with newly diagnosed and gluten-free diet-treated celiac disease

Elucidating Immune Cell Changes in Celiac Disease: Revealing New Insights from Spectral Flow Cytometry

Celiac disease (CD) is an immune-mediated enteropathy of the small intestine triggered by gluten ingestion. Although the small bowel is the main organ affected, peripheral blood cell alterations have also been described in CD. We aimed to investigate immunological cell patterns in the blood of treated CD patients and in response to a 3-day gluten challenge (GC). Blood samples were collected from 10 patients with CD and 8 healthy controls on a gluten-free diet at baseline and 6 days after initiating the GC. All the samples were analyzed by spectral flow cytometry using a 34-marker panel. We found that patients with CD displayed a lower proportion of memory B cells compared to healthy controls, both at baseline and post-GC. Additionally, we observed the previously reported activated gut-homing CD4+, CD8+, and TCRγδ+ T lymphocytes on day 6 post-GC, and found the CD8+ subpopulation to be the most readily identifiable by flow cytometry. Importantly, the CCR9 marker proved effective in enhancing the selection of these gluten-responsive T cells, offering the potential for increased diagnostic accuracy. Spectral flow cytometry involves a complex data analysis, but it offers valuable insights into previously unexplored immunological responses and enables in-depth cell characterization.

The Emerging Role of Innate Lymphoid Cells (ILCs) and Alarmins in Celiac Disease: An Update on Pathophysiological Insights, Potential Use as Disease Biomarkers, and Therapeutic Implications

Celiac disease (CD) is an intestinal disease that develops in genetically predisposed individuals and is triggered by the ingestion of gluten. CD was considered a Th1-disease. Today, the role of Th17, IL-21, and IL-17A lymphocytes is well known. Inflammation is regulated by the activity of gluten-specific CD4+ T lymphocytes that produce pro-inflammatory cytokines, including IFN-γ, TNF-α, and IL-21, perpetuating the Th1 response. These cytokines determine an inflammatory state of the small intestine, with consequent epithelial infiltration of lymphocytes and an alteration of the architecture of the duodenal mucosa. B cells produce antibodies against tissue transglutaminase and against deamidated gliadin. Although the role of the adaptive immune response is currently known, the evidence about the role of innate immunity cells is still poorly understood. Epithelial damage determines the release of damage-associated molecular patterns (DAMPs), also known as alarmins. Together with the intestinal epithelial cells and the type 1 innate lymphoid cells (ILC1s), alarmins like TSLP, IL-33, and HMGB1 could have a fundamental role in the genesis and maintenance of inflammation. Our study aims to evaluate the evidence in the literature about the role of ILCs and alarmins in celiac disease, evaluating the possible future diagnostic and therapeutic implications.

Toll-like Receptors and Celiac Disease

Celiac disease (CD) is an immune-mediated disorder triggered by dietary gluten intake in some genetically predisposed individuals; however, the additional non-HLA-related genetic factors implicated in CD immunopathogenesis are not well-defined. The role of the innate immune system in autoimmunity has emerged in the last few years. Genetic polymorphisms of some pattern-recognition receptors, including toll-like receptors (TLRs), have been associated with several autoimmune disorders. In this review, we summarize and discuss the evidence from basic research and clinical studies as regards the potential role of TLRs in CD immunopathogenesis. The evidence supporting the role of TLRs in CD immunopathogenesis is limited, especially in terms of basic research. However, differences in the expression and activation of TLRs between active CD patients from one side, and controls and treated CD patients from the other side, have been described in some clinical studies. Therefore, TLRs may be part of those non-HLA-related genetic factors implicated in CD etiopathogenesis, considering their potential role in the interaction between the host immune system and some environmental factors (including viral infections and gut microbiota), which are included in the list of candidate agents potentially contributing to the determination of CD risk in genetically predisposed individuals exposed to dietary gluten intake. Further basic research and clinical studies focused on TLRs in the context of CD and other gluten-related disorders are needed.

Gliadin-reactive vitamin D-sensitive proinflammatory ILCPs are enriched in celiac patients

Celiac disease (CD) is a multisystem disease in which different organs may be affected. We investigate whether circulating innate lymphoid cells (ILCs) contribute to the CD peripheral inflammatory status. We find that the CD cytokine profile is characterized by high concentrations of IL-12p40, IL-18, and IFN-γ, paralleled by an expansion of ILC precursors (ILCPs). In the presence of the gliadin peptides p31-43 and pα-9, ILCPs from CD patients increase transglutaminase 2 (TG2) expression, produce IL-18 and IFN-γ, and stimulate CD4⁺ T lymphocytes. IFN-γ is also produced upon stimulation with IL-12p40 and IL-18 and is inhibited by the addition of vitamin D. Low levels of blood vitamin D correlate with high IFN-γ and ILCP presence and mark the CD population mostly affected by extraintestinal symptoms. Dietary vitamin D supplementation appears to be an interesting therapeutic approach to dampen ILCP-mediated IFN-γ production.

The Transcriptomic Analysis of Circulating Immune Cells in a Celiac Family Unveils Further Insights Into Disease Pathogenesis

Celiac disease (CD), the most common chronic enteropathy worldwide, is triggered and sustained by a dysregulated immune response to dietary gluten in genetically susceptible individuals. Up to date either the role of environmental factors and the pathways leading to mucosal damage have been only partially unraveled. Therefore, we seized the unique opportunity to study a naturally-occurring experimental model of a family composed of both parents suffering from CD (one on a gluten-free diet) and two non-celiac daughters. The control group consisted in four unrelated cases, two celiac and two non-celiac subjects, all matching with family members for both disease status and genetic susceptibility. In this privileged setting, we sought to investigate gene expression in peripheral blood mononuclear cells (PBMCs), a population known to mirror the immune response state within the gut. To this purpose, PBMCs were obtained from the four biopsied-proven CD patients and the four non-celiac cases. Each group included two family members and two unrelated control subjects. After RNA purification and cDNA synthesis, each sample underwent a microarray screen on a whole-transcriptome scale, and the hybridization results were visualized by hierarchical clustering. Differentially expressed genes (DEG) were partitioned into clusters displaying comparable regulations among samples. These clusters were subjected to both functional and pathway analysis by using the Kyoto Encyclopedia of Genes and Genomes. Interestingly, on a global gene expression level, the family members clustered together, regardless of their disease status. A relevant fraction of DEG belonged to a limited number of pathways, and could be differentiated based on disease status: active CD vs. treated CD and CD vs. controls. These pathways were mainly involved in immune function regulation, cell-cell junctions, protein targeting and degradation, exosome trafficking, and signal transduction. Worth of noting, a small group of genes mapping on the male-specific region of the Y chromosome, and previously linked to cardiovascular risk, was found to be strongly upregulated in the active CD case belonging to the family, who suddenly died of a heart attack. Our results provide novel information on CD pathogenesis and may be useful in identifying new therapeutic tools and risk factors associated with this condition.

Amylase-Trypsin Inhibitors in Wheat and Other Cereals as Potential Activators of the Effects of Nonceliac Gluten Sensitivity

Nonceliac gluten sensitivity (NCGS) is a gluten-related gastrointestinal disorder distinct from celiac disease (CD) and gluten allergy that is not easy to diagnose due to the lack of biomarkers. It is characterized by intestinal symptoms and extraintestinal manifestations with the consumption of gluten-containing foods. In contrast to CD, NCGS patients do not present a genetic predisposition or intestinal villi atrophy. Recent studies question the proinflammatory triggering activity of α-gliadin fraction contained in wheat, since it has been demonstrated that the amylase-trypsin inhibitors (ATIs) exert a strong activating effect on the innate immune response. We aimed to analyze the role of ATIs in the activation of innate immunity and in the development of the symptoms characteristic of NCGS. A systematic literature search was made using databases such as MEDLINE, SciELO, Science Direct, and Scopus, with focus on key words such as "amylase-trypsin inhibitors," "wheat," "gluten," and "celiac." Many studies are available on the structure, inhibition mechanism, and immune system effects of ATIs, mainly focused on IgE-mediated reactions. Recently, with the increase of NCGS interest, has increased the literature on the capacity of ATIs contained in wheat to activate the innate immune system. Literature published to date questions the relationship between activation of the innate immune system and gluten in NCGS. ATIs may have acted as interfering contaminant of gluten and appear as potential activator of innate immunity in NCGS patients. In view of their potential impact, more interventional studies are needed to demonstrate the proinflammatory effect of ATIs.

Double-blind, randomised, placebo-controlled intervention trial to evaluate the effects of Bifidobacterium longum CECT 7347 in children with newly diagnosed coeliac disease

Interactions between the immune system and the intestinal microbiota may play a role in coeliac disease (CD). In the present study, the potential effects of Bifidobacterium longum CECT 7347 in children with newly diagnosed CD were evaluated. A double-blind, randomised, placebo-controlled trial was conducted in thirty-three children who received a capsule containing either B. longum CECT 7347 (10⁹ colony-forming units) or placebo (excipients) daily for 3 months together with a gluten-free diet (GFD). Outcome measures (baseline and post-intervention) included immune phenotype of peripheral blood cells, serum cytokine concentration, faecal secretory IgA (sIgA) content, anthropometric parameters and intestinal microbiota composition. Comparisons between the groups revealed greater height percentile increases (P= 0·048) in the B. longum CECT 7347 group than in the placebo group, as well as decreased peripheral CD3⁺ T lymphocytes (P= 0·004) and slightly reduced TNF-α concentration (P= 0·067). Within-group comparisons of baseline and final values did not reveal any differences in T lymphocytes and cytokines in the placebo group, while decreased CD3⁺ (P =0·013) and human leucocyte antigen (HLA)-DR⁺ T lymphocytes (P =0·029) and slightly reduced TNF-α concentration (P= 0·085) were detected in the B. longum CECT 7347 group. Comparison between the groups showed that the administration of B. longum CECT 7347 reduced the numbers of the Bacteroides fragilis group (P= 0·020) and the content of sIgA in stools (P= 0·011) compared with the administration of placebo. Although this is a first exploratory intervention with limitations, the findings suggest that B. longum CECT 7347 could help improve the health status of CD patients who tend to show alterations in gut microbiota composition and a biased immune response even on a GFD.

Milestones in understanding of the pathogenesis of immunmediated intestinal disorders. Development of their diagnosis and therapy

In the last decades our knowledge has been enormously broadened about the structure and function of the gut associated lymphoid system. It was recognized how intricate and finely tuned connection exists between the gut bacterial flora and the intestinal mucosa. This subtle balance ensures mucosal homeostasis, which has a key role in organ defence against pathogens. However, at the same time this system makes possible the development of oral tolerance toward the commensals and the food antigens. In case of any disturbances in this finely tuned process, immunmediated intestinal disorders may easily develop. The first part of this paper reviews the structure and function of the mucosal immune system, while the second part surveys the pathogenesis, diagnosis and therapy of coeliac disease, inflammatory bowel disease and cow’s milk allergy induced enteropathy. Orv. Hetil., 2013, 154, 1512–1523.

Pepsin digest of wheat gliadin fraction increases production of IL-1β via TLR4/MyD88/TRIF/MAPK/NF-κB signaling pathway and an NLRP3 inflammasome activation

Celiac disease (CD) is a gluten-responsive, chronic inflammatory enteropathy. IL-1 cytokine family members IL-1β and IL-18 have been associated with the inflammatory conditions in CD patients. However, the mechanisms of IL-1 molecule activation in CD have not yet been elucidated. We show in this study that peripheral blood mononuclear cells (PBMC) and monocytes from celiac patients responded to pepsin digest of wheat gliadin fraction (PDWGF) by a robust secretion of IL-1β and IL-1α and a slightly elevated production of IL-18. The analysis of the upstream mechanisms underlying PDWGF-induced IL-1β production in celiac PBMC show that PDWGF-induced de novo pro-IL-1β synthesis, followed by a caspase-1 dependent processing and the secretion of mature IL-1β. This was promoted by K+ efflux and oxidative stress, and was independent of P2X7 receptor signaling. The PDWGF-induced IL-1β release was dependent on Nod-like receptor family containing pyrin domain 3 (NLRP3) and apoptosis-associated speck like protein (ASC) as shown by stimulation of bone marrow derived dendritic cells (BMDC) from NLRP3(-/-) and ASC(-/-) knockout mice. Moreover, treatment of human PBMC as well as MyD88(-/-) and Toll-interleukin-1 receptor domain-containing adaptor-inducing interferon-β (TRIF)(-/-) BMDC illustrated that prior to the activation of caspase-1, the PDWGF-triggered signal constitutes the activation of the MyD88/TRIF/MAPK/NF-κB pathway. Moreover, our results indicate that the combined action of TLR2 and TLR4 may be required for optimal induction of IL-1β in response to PDWGF. Thus, innate immune pathways, such as TLR2/4/MyD88/TRIF/MAPK/NF-κB and an NLRP3 inflammasome activation are involved in wheat proteins signaling and may play an important role in the pathogenesis of CD.

Unraveling the ties between celiac disease and intestinal microbiota

Celiac disease is a multifactorial disorder that involves interactions between genetic and environmental factors. Gluten proteins are responsible for the symptoms of celiac disease, but other environmental factors that influence the intestinal ecosystem, including the milk-feeding type and gastrointestinal infections, may also play a role. Moreover, intestinal dysbiosis, characterized by increased Gram-negative bacteria and reduced bifidobacteria, has been detected in celiac disease patients. This review summarizes current knowledge of the associations between the intestinal microbiota and celiac disease and its possible modes of action in pathogenesis. Deeper understanding of these interactions can help redefine how this disorder is investigated.

Dynamics of non-conventional intraepithelial lymphocytes-NK, NKT, and γδ T-in celiac disease: relationship with age, diet, and histopathology

BACKGROUND

Intraepithelial lymphocytes (IEL) are a heterogeneous population of lymphocytes raised in celiac disease (CD), whose role in CD pathogenesis remains to be defined.

AIMS

To investigate how the age of diagnosis, diet, and the severity of the histological lesions are related to the changes observed in unconventional IEL populations.

METHODS

Prospective analysis of 101 confirmed celiac patients from a single center, including 66 at diagnosis (45 children, 21 adults) and 112 non-celiac controls (12 children, 100 adults). IEL from duodenal biopsies were studied by six-color flow cytometry. The results were analyzed in relationship with age, diet (gluten intake), and histopathology (Marsh type).

RESULTS

In comparison with respective age controls, both children and adult patients showed duodenal intraepithelial lymphocytosis with significant differences in every single non-conventional IEL population: CD3+ TCR γδ, NK (CD3-, CD16+, CD56+), NKT (CD3+, CD161+, CD56+), and iNKT (CD3+ Vα24) (P < 0.001 for all). Gluten intake was not only directly associated with severe atrophy, but also with decreased percentages of NK (P = 0.02), NKT (P = 0.003), and iNKT (P = 0.03). Changes in iNKT and γδ IEL were more marked in celiac children compared with celiac adults (P = 0.02 and 0.01, respectively). In contrast, increased CD3+ TCR γδ were diet- and Marsh grade-independent.

CONCLUSIONS

The typical phenotypical profile of intraepithelial lymphocytosis in untreated pediatric and adult celiacs consists of increased CD3+ TCR γδ populations with decreased NK, NKT, and iNKT cells. NK, NKT, and iNKT IEL, but not γδ IEL, are dynamic populations associated with diet, age, and histopathology.