Immunopathology of gluten-sensitive enteropathy

Local ocular surface parameters in patients with systemic celiac disease

PurposeThis was a collaborative study from the Ophthalmology and Gastroenterology departments of a tertiary care hospital, designed to investigate the local ocular surface parameters in patients with celiac disease (CD).MethodsFifty-six eyes of 28 patients with CD and 58 eyes of 29 healthy adult subjects serving as controls were evaluated. The Schirmer test, tear-film break-up time, and conjunctival impression cytology were performed in addition to a complete ophthalmological examination. Impression cytology specimens of each group were graded and scored in the range 0-3.ResultsThe 28 patients with CD consisted of 24 females (86%) and 4 males (14%). The mean age was 34.4±11.3 years (22-55 years). Tear-film break-up time and Schirmer test results were significantly lower in the study group than in the controls (P<0.05). Also, there was a significant difference between the groups for impression cytology grading scores (P=0.001).ConclusionsThe CD group showed a marked preponderance of females with an F/M ratio of six females per male, as reported in the literature. Tear-film functions and conjunctival surface epithelial morphology were significantly altered in patients with CD.

The changing immunological paradigm in coeliac disease

When coeliac disease is referred to as an inflammatory disorder, this may detract from its true nature. Activation of innate and adaptive immunity takes place in the mucosal lesion, but the tissue reaction is not that of classical inflammation. In fact, coeliac disease contrasts strikingly with typical inflammatory bowel disorders such as ulcerative colitis and Crohn's disease. The coeliac lesion apparently reflects, in the main, immune-driven remodelling of mucosal architecture with only a minor inflammatory component - initially most likely resulting from innate signals. Complement split products might be one of several potential initial hits that lead to activation of lamina propria and epithelial cells with release of mediators such as interleukin-15. This cytokine appears to stimulate potentially pathogenic intraepithelial lymphocytes. In genetically susceptible individuals, such early innate events could turn into persistent pathogenic signalling with subsequent adaptive cellular and humoral immunopathology resulting in a chronic lesion. Nevertheless, mucosal homeostasis is surprisingly well preserved as signified by the remarkable dominance of plasma cells that produce dimeric immunoglobulin A as a basis for enhanced secretory immunity. This shows that the microvascular endothelium in the lesion largely maintains its 'gatekeeper' function for mucosal immune cells - in striking contrast to the 'promiscuous' situation in inflammatory bowel disease. Altogether, a two-signal model is emerging for the pathogenesis of coeliac disease - signal 1 generated by innate immunity and signal 2 by adaptive immunity. Hence, there is currently an increased focus on immune activation in the epithelial compartment rather than on changes in the microvasculature as a basis for classical inflammation.

Coeliac disease in Sjögren's syndrome--a study of 111 Hungarian patients

Recent studies report that in patients with Sjögren's syndrome (SS), concomitant coeliac disease (CD) is more frequent than in the average healthy population, with dominance of the latent/silent form. We further investigated this to characterise the clinical and immunolaboratory features of SS patients with CD. One hundred and eleven patients with SS were involved in the study. After detailed history, blood samples were taken for antibodies to gliadin, endomysium, and tissue transglutaminase. Of them, six had positive serology for CD and underwent jejunoscopy and small bowel biopsy to confirm the diagnosis of CD. In five patients, the diagnosis was established histologically. The frequency of CD in the SS population was significantly higher than in the non-SS European population (4.5:100 vs 4.5-5.5:1,000). Laboratory findings in these patients showed significantly higher erythrocyte sedimentation rates and IgG, IgA, and IgM levels. On the basis of these findings, we recommend screening, follow-up, and regular gastrointestinal care of SS patients to identify CD cases and help them to avoid severe malnutrition and intestinal malignancies.

Role of the polymeric Ig receptor in mucosal B cell homeostasis

Secretory IgA (SIgA) is the most characteristic component of the mucosal immune system and has long been considered the major protective factor that prevents pathogens from invading hosts through the mucosae. Recent studies, however, have suggested that complete immunity against a range of mucosal bacterial and viral pathogens can be achieved in the absence of IgA. Therefore, to further dissect the role of SIgA, we generated mice deficient in the polymeric Ig receptor (pIgR(-/-) mice). As a result of an inability to transport dimeric IgA to the secretions, pIgR(-/-) mice are deficient in SIgA and accumulate circulating dimeric IgA, with serum levels 100-fold greater than those observed in normal mice. Examination of lamina propria mononuclear cells showed that pIgR(-/-) mice had approximately 3 times as many IgA-secreting cells as C57BL/6 mice. Further analysis showed that these cells displayed the differentiated IgA(+) B220(-) phenotype and accounted for a 2-fold increase in the number of lamina propria blast cells in the pIgR(-/-) mice. Subsequent experiments showed that OVA-specific CD4(+) T cell expansion following OVA feeding was not elevated in pIgR(-/-) mice. Furthermore, no differences in CD8(+) T cell tolerance or induction of influenza virus-specific CD8(+) T cells were detected in pIgR(-/-) mice compared with controls. Therefore, while SIgA is clearly involved in maintaining some parameters of mucosal homeostasis in the intestine, the mechanisms associated with its barrier function and the clinical consequences of its deficiency are yet to be identified.

Interferon-gamma-secreting T cells localize to the epithelium in coeliac disease

Increased levels of interferon-gamma (IFN-gamma) transcripts have previously been found in duodenal biopsy specimens from patients with untreated coeliac disease (CD). Such samples and duodenal control mucosa were therefore studied to locate and phenotype cells spontaneously secreting IFN-gamma. Specimens were collected from consecutively recruited patients with untreated (seven), treated (four) or refractory (three) CD and from five histologically normal controls. Morphological and immunohistochemical examinations were performed, and epithelial and lamina propria cell suspensions were prepared from parallel samples. Unstimulated viable cells secreting IFN-gamma were identified and phenotyped with a new fluorescence-activated cell sorter-based assay, and IFN-gamma messenger RNA (mRNA) was analysed in snap-frozen aliquots of the same suspensions. Untreated CD cases had the highest fraction of IFN-gamma+ cells in the epithelial compartment (median 2.6%, range 1.6-6.2%) and, less strikingly, in the lamina propria compartment (1.6%, range 0.3-3.6%), followed by refractory (1.4%, 1.0-1.9%; and 0.3%, 0.0-1.2%) and treated (0.8%, 0.5-0.9%; and 0.7%, 0.2-1.1%) disease and finally the controls (0.5%, 0.3-0.9%; and 0.2%, 0.1-0.7%). IFN-gamma mRNA data supported these findings. IFN-gamma+ intraepithelial lymphocytes were mostly CD3+ and CD8+, whereas many positive lamina propria cells were CD8-. We conclude that isolated T cells spontaneously secreting IFN-gamma localize preferentially in the epithelium of patients with classical and refractory CD.

Transforming growth factor-beta (TGF-beta) and tissue transglutaminase expression in the small intestine in children with coeliac disease

The production of cytokines from T cells and macrophages is of potential importance for the histological changes apparent in coeliac disease (CoD). Small intestinal biopsy specimens from children with CoD and disease control subjects were investigated for their content of cytokines and tissue transglutaminase (tTG). The transforming growth factor-beta1 (TGF-beta1) expression was increased in the lamina propria of children with villous atrophy. In contrast, TGF-beta3 was expressed at a higher level in the epithelium and the lamina propria of the disease control subjects. The tTG expression was increased in the small intestine of CoD patients as compared with that in subjects. Interleukin-4 (IL-4) was detected in the lamina propria of both CoD patients and controls, and some of the investigated biopsy specimens also showed IL-4 expression in the epithelium. We conclude that children with active CoD could have an altered expression of TGF-beta and tTG in the small intestine and that a disturbed regulation of TGF-beta may be of importance in the immune pathogenesis of CoD.

Gene polymorphisms, inflammatory diseases and cancer

Genes whose products play a critical role in regulation of the immune response include the human leucocyte antigen (HLA) and cytokine families of genes. The HLA genes are the most polymorphic found in the human genome, and the bulk of this polymorphism results in functional differences in expressed HLA molecules, resulting in inter-individual differences in presentation of peptide antigens to T-cells. In addition, a considerable number of cytokine-associated gene polymorphisms have been identified, the bulk of which occur in the upstream promoter sequences of these genes, which in many cases results in differential in vitro expression of the respective pro- or anti-inflammatory gene product. Particular HLA polymorphisms result in well-defined associations with a large number of immunologically-mediated diseases, including some diseases with known dietary risk factors. For example, individuals of HLA-DQA1*0501, DQB1*0201 genotype have a greater than 200-fold increased risk of developing intolerance to dietary wheat gluten (coeliac disease), and additional HLA-related factors may influence the development of malignant lymphoma within pre-existing coeliac disease. Similarly, HLA-DRB1 alleles sharing a common sequence motif constitute the primary known genetic risk factor for rheumatoid arthritis. The influence of polymorphisms associated with differential cytokine expression on disease susceptibility is currently of much interest. Most attention has been focused on associations with susceptibility to benign immunologically-mediated diseases, including a number of gut diseases. However, recent work from our laboratory indicates that cytokine polymorphisms may influence susceptibility to and prognosis in a number of different cancers, including malignant melanoma skin cancer and solid tumours which may be influenced by diet, such as prostate cancer (collaboration with the CRC/BPG UK Familial Prostate Cancer study). In addition, preliminary work suggests that dietary modulation of expression levels of certain cytokines in healthy human subjects may be genotype dependent.

Current understanding of gastrointestinal immunoregulation and its relation to food allergy

Tolerance to food antigens induced via the gut ("oral tolerance") appears to be a rather robust adaptive immune mechanism. However, the neonatal period is particularly critical in terms of mucosal defense, with regard to infections and priming for allergic disease. This is so because the intestinal barrier function provided by secretory antibodies, as well as the immunoregulatory network, is poorly developed for a variable period after birth. Notably, the postnatal development of mucosal immune homeostasis depends on the establishment of a normal commensal microbial flora and also on adequate timing and dose of dietary antigens when first introduced. In this context, breastfeeding appears to exert both shielding and positive regulatory effects. Altogether, the intestinal immune system normally seems rather fit for tolerance induction against innocuous antigens because most children with food allergy "outgrow" their problems, whereas airway allergy tends to persist.

T-Independent IgA Responses to Microbial Polysaccharides

There is accumulating evidence indicating the presence in vivo of T-independent routes of IgA response in addition to the conventional T-dependent IgA response. Factors influencing these alternative pathways of IgA responses may include the structural characteristics of a stimulating antigen, the nature of responding B cells, and the microenvironment. The structural complexity of polysaccharide antigens has made it difficult to summarize a general scheme for the antibody responses they induce. Instead, one may expect that each individual polysaccharide may be able to create a unique microenvironment by activation of specific cell populations in the repertoires of non-T cell types. A specific pattern of B cell response may thus be elicited by TI stimulation. Recognition of such a unique property of a TI antigens is necessary for us to better understand the T-independent IgA response. Information obtained may have an impact on the development of vaccination strategies directed at the mucosal immunity mediated by IgA antibodies.

Interleukin 15 mediates epithelial changes in celiac disease

BACKGROUND & AIMS

Villous atrophy and crypt proliferation are key epithelial features of untreated celiac disease. We tried to define whether cytokines such as interleukin (IL)-15, IL-2, IL-4, and IL-7, which share chains of their receptors, could influence the epithelial modifications.

METHODS

Duodenal biopsy specimens (14 treated and 13 untreated celiac patients, 7 controls) were cultured in vitro for 24 hours with or without gliadin (1 mg/mL), IL-15, IL-7, IL-4, or IL-2 (10 ng/mL). Tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma were also used in some specimens of untreated celiacs. Epithelial expression of Ki67, FAS, and transferrin receptor (TFR) was detected by immunohistochemistry, and apoptosis by TUNEL technique (percentage of positive enterocytes). IL-15-positive cells were detected by immunohistochemistry in celiac disease and control biopsy specimens; presence of IL-15 was also determined by semiquantitative polymerase chain reaction.

RESULTS

Only IL-15 induced enterocyte expression of Ki67, TFR, and FAS in treated celiac (P<0.01 vs. medium) and enterocyte apoptosis in untreated celiac disease specimens. Anti-IL-15 monoclonal antibodies neutralized gliadin-induced enterocyte TFR and FAS expression in treated celiac and enterocyte apoptosis in untreated celiac disease specimens (P<0.05 vs. gliadin). IL-15-positive cells were increased in untreated celiacs (P<0.001 vs. treated celiacs and controls).

CONCLUSIONS

IL-15 is involved in the modulation of epithelial changes in celiac disease, indicating that this cytokine has an unforeseen role in the pathologic manifestations of celiac disease.

Evidence of chronic inflammation in morphologically normal small intestine of cystic fibrosis patients

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator gene and characteristically leads to prominent lung and pancreatic malfunctions. Although an inflammatory reaction is normally observed in the CF airways, no studies have been performed to establish whether a chronic inflammatory response is also present in the CF intestine. We have investigated whether immunologic alterations and signs of inflammation are observed in CF small intestine. Fourteen CF, 20 negative, and four disease controls underwent duodenal endoscopy for diagnostic purposes. Two CF patients were rebiopsied, one after 3 mo of an elemental diet and the other after 2 wk of pancreatic enzyme withdrawal. In three CF and 10 controls, in vitro small intestine organ cultures were also performed. Expression of ICAM-1, IL-2 receptor, IL-2, IFN-gamma, CD80, and transferrin receptor was studied by immunohistochemistry before and after in vitro organ culture. In CF small intestine, an increased number of lamina propria mononuclear cells express ICAM-1 [mean 114 (SD 82.8), p < 0.001 versus controls], CD25 [20.2 (18.7), p < 0.01], IL-2 [23.6 (13.7), p < 0.05], and IFN-gamma [19 (15.9), p < 0.05], whereas villus enterocytes highly express transferrin receptor. Reduced expression of immunologic markers was observed after 24 h of in vitro culture in all three CF patients as well as in the patient kept on elemental diet for 3 mo. These results indicate that chronic inflammation is observed in CF duodenum and suggest that the perturbation of local mucosal immune response may contribute to the overall clinical picture in CF patients.

Absence of epithelial immunoglobulin A transport, with increased mucosal leakiness, in polymeric immunoglobulin receptor/secretory component-deficient mice

Mucosal surfaces are protected specifically by secretory immunoglobulin A (SIgA) and SIgM generated through external translocation of locally produced dimeric IgA and pentameric IgM. Their active transport is mediated by the epithelial polymeric Ig receptor (pIgR), also called the transmembrane secretory component. Paracellular passive external transfer of systemic and locally produced antibodies also provides mucosal protection, making the biological importance of secretory immunity difficult to assess. Here we report complete lack of active external IgA and IgM translocation in pIgR knockout mice, indicating no redundancy in epithelial transport mechanisms. The knockout mice were of normal size and fertility but had increased serum IgG levels, including antibodies to Escherichia coli, suggesting undue triggering of systemic immunity. Deterioration of their epithelial barrier function in the absence of SIgA (and SIgM) was further attested to by elevated levels of albumin in their saliva and feces, reflecting leakage of serum proteins. Thus, SIgA did not appear to be essential for health under the antigen exposure conditions of these experimental animals. Nevertheless, our results showed that SIgA contributes to maintenance of mucosal homeostasis. Production of SIgA might therefore be a variable in the initiation of human immunopathology such as inflammatory bowel disease or gluten-sensitive enteropathy.

The B-cell system of human mucosae and exocrine glands

The mucosae and exocrine glands harbour the largest activated B-cell system of the body, amounting to some 80-90% of all immunoglobulin (Ig)-producing cells. The major product of these immunocytes is polymeric (p)IgA (mainly dimers) with associated J chain. Both pIgA and pentameric IgM contain a binding site for the polymeric Ig receptor (pIgR), or secretory component (SC), which is a requirement for their active external transport through secretory epithelia. The pIgR/SC binding site depends on covalent incorporation of the J chain into the quaternary structure of the polymers when they are produced by the local immunocytes. This important differentiation characteristic appears to be sufficient functional justification for the J chain to be expressed also by most B cells terminating at secretory effector sites with IgD or IgG production; they probably represent a "spin-off" from sequential downstream CH switching on its way to pIgA expression, thus apparently reflecting a maturational stage of effector B-cell clones compatible with homing to these sites. Observations in IgA-deficient individuals suggest that the magnitude of this homing is fairly well maintained even when the differentiation pathway to IgA is blocked. Certain microenvironmental elements such as specific cytokines and dendritic cells appear to be required for induction of IgA synthesis, but it remains virtually unknown why this isotype normally is such a dominating product of local immunocytes and why they have such a high level of J chain expression. Also, despite the recent identification of some important requirements in terms of adhesion molecules (e.g. integrin alpha 4 beta 7 and MAdCAM-1) that explain the "gut-seeking" properties of enterically induced B cells, the origin of regionalized homing of B cells to secretory effector sites outside the gut remains elusive. Moreover, little is known about immune regulation underlying the striking disparity of both the class (IgD, IgM) and subclass (IgA1, IgA2, IgG1, IgG2) production patterns shown by local immunocytes in various regions of the body, although the topical microbiota and other environmental stimuli might be important. Rational design of local vaccines will depend on better knowledge of both inductive and migratory properties of human mucosal B cells.

Celiac disease in relation to immunologic serum markers, trace elements, and HLA-DR and DQ antigens in Swedish children with Down syndrome

BACKGROUND

An association between Down syndrome and celiac disease has been reported. This study was conducted to determine the association between childhood celiac disease and Down syndrome in the county of Uppsala, Sweden.

METHODS

All 76 children with Down syndrome (1-18 years) were screened for the occurrence of anti-gliadin antibodies (AGA) and anti-endomysium antibodies (EMA). Twelve children with suspected celiac disease were investigated further.

RESULTS

Increased levels of both IgA and IgG AGA were found in 26% of the children and of EMA in and 5 of 76. Celiac disease was diagnosed in at least three of the children (3.9%; 95% confidence interval 0%-8.3%), and it could have been present in as many as eight. Three of the five EMA-positive children with suspected celiac disease had the HLA phenotype DR3, DQ2.

CONCLUSIONS

The results show that determination of EMA is more useful as a screening test for celiac disease and for follow-up than is AGA in children with Down syndrome. The present study also confirms that celiac disease is overrepresented among Swedish children with Down syndrome and that celiac disease should be considered in all persons with Down syndrome.

Cytokine-producing cells in peripheral blood of children with coeliac disease secrete cytokines with a type 1 profile

Coeliac disease (CoD) is a small intestinal disorder characterized by crypt cell hyperplasia and villous atrophy, and the production of cytokines from T cells and macrophages are of importance for the histological changes seen in CoD. A peroral immunization with an antigen, which gives rise to a mucosal immune response, may increase the levels of circulating cytokine-producing cells, and we wanted to obtain a better picture of an eventual emergence of activated circulating T cells in the peripheral blood in children with CoD. The cytokine expression of interferon-gamma (IFN-gamma), IL-4, IL-6 and IL-10 was measured at the single-cell level by an ELISPOT method in 38 children with CoD. The numbers of IFN-gamma-producing cells in the peripheral blood was increased in children with untreated CoD (P < 0.01) and after gluten challenge (P < 0.05) compared with healthy controls. Also, the numbers of IL-6-producing cells were increased (P < 0.05) after gluten challenge compared with the healthy controls. A paired comparison showed that the numbers of IFN-gamma-producing cells increased after gluten challenge (P < 0.05), whereas no such change was seen for IL-4- or IL-10-producing cells. There were no differences in the numbers of IFN-gamma-producing cells between the group of children with treated CoD and the groups of untreated or challenged CoD children. IL-4 production correlated with serum levels of total IgE. These results show that circulating mononuclear cells in children with active CoD secrete cytokines compatible with a type 1 response.

Cytokine profile in coeliac disease

Coeliac disease (CD), an inflammatory enteropathy, is believed to be caused by immune sensitivity to ingested gluten. T-cell activation appears to be implicated in the disease although little is known regarding the role of T-cell subsets, Th1/Th2, and the cytokines they secrete. Reverse transcription-polymerase chain reaction was used to examine the mRNA expression of a wide profile of cytokines in intestinal and peripheral samples taken from active and inactive CD paediatric patients. Differential mRNA expression was observed for cytokines, between CD patients and controls, in both compartments. The percentage of samples expressing interleukin (IL)-2, interferon (IFN)-gamma, tumor necrosis factor (TNF)-beta, IL-10, IL-1beta, TNF-alpha and transforming growth factor (TGF)-beta mRNA from active CD patients was higher than from controls. A prominent finding was the expression of both Th1 (IFN-gamma, IL-2) and Th2 (IL-4, IL-10)-associated cytokine transcripts in the same biopsies and peripheral blood cells from patients with active CD implying activation of Th0 cells. The expression of IL-2 and IL-4 mRNA was not observed in peripheral blood samples from inactive CD patients associating them with disease activity. These results are important to the understanding of the inflammatory process in CD while cytokine levels may prove to be relevant markers of disease activity.

Gluten induces an intestinal cytokine response strongly dominated by interferon gamma in patients with celiac disease

BACKGROUND & AIMS

Celiac disease appears to be a T cell-mediated enteropathy induced by gluten in genetically predisposed individuals. Duodenal biopsy specimens from patients with celiac disease and histologically normal controls were investigated to see if cytokine expression is related to disease activity.

METHODS

Cytokine messenger RNA (mRNA) expression was determined by quantitative reverse-transcription polymerase chain reaction and in situ expression by immunohistochemistry.

RESULTS

In normal controls, mRNA levels were usually below the quantitative limit, even after in vitro gluten stimulation. By contrast, interferon (IFN)-gamma mRNA was increased more than 1000-fold in untreated disease. In vitro gluten stimulation of specimens from treated patients (gluten-free diet) increased IFN-gamma mRNA to the levels of untreated patients. In addition, increased mRNA levels for interleukin (IL)-2, IL-4, IL-6, and tumor necrosis factor alpha were found after such stimulation, whereas mRNA for IL-5, IL-10, and IL-12p40 was usually below the quantitative level. Biopsy specimens from untreated patients contained on average 10-fold more lamina propria cells positive for IFN-gamma than normal controls, whereas cells containing IL-4 were rare in both subject groups.

CONCLUSIONS

The results show that mucosal gluten exposure in patients with celiac disease rapidly elicits high levels of IFN-gamma expression and lower levels of IL-2, IL-4, IL-6, and tumor necrosis factor alpha even in the virtual absence of IL-12.