Immune response to gluten in adult coeliac disease

Deficiency of 6B11+ invariant NK T-cells in celiac disease

Immunoregulatory NK T-cells are deficient in certain autoimmune diseases. The purpose of this study was to investigate any deficiency of immunoregulatory NK T-cells in celiac disease. NK T-cells were identified by flow cytometry with 6B11 and V alpha 24 markers in blood from 18 normal and 12 celiac subjects. Blood mononuclear cells were stimulated with anti-CD3/CD28 antibodies and intracellular cytokines assessed at 4 h in seven normal and eight celiac subjects. V alpha 24/GAPDH mRNA was quantitated in duodenal biopsies by real time PCR in 17 control and 13 celiac subjects. NK T-cells in celiac subjects were reduced to 30% of those in normal subjects. Intracellular IL-4, IL-10 and IL-13 increased significantly by 33-41% in normal subjects, but did not change in celiac subjects. V alpha 24/GAPDH mRNA from celiac subjects was reduced to 5% of levels in control subjects. We conclude that immunoregulatory NK T-cells are deficient in celiac disease.

Deficiency of invariant natural killer T cells in coeliac disease

BACKGROUND

Immunoregulatory invariant natural killer (iNK) T cells rapidly produce interleukin (IL)-4 and other cytokines that suppress a Th1 response and are deficient in some autoimmune diseases.

AIM

The aim of this study was to investigate any deficiency of iNK T cells in coeliac disease.

METHODS

Blood was collected from 86 subjects with coeliac disease and from 152 healthy control subjects for investigation of Valpha24+ T cells by flow cytometry. iNK T cells were assessed by Valpha24 and alpha-galactosylceramide/CD1d tetramer markers in 23 normal controls and 13 subjects with coeliac disease. Intracellular IL-4 was measured after anti-CD3 antibody stimulation. Duodenal biopsies were obtained in a subgroup of subjects with coeliac disease and control subjects for Valpha24 mRNA expression using relative PCR and for Valpha24+ T cells by immunofluorescence.

RESULTS

The mean numbers of circulating Valpha24+ T cells and iNK T cells in coeliac disease were 27% (p<0.001) and 16% (p<0.001), respectively, of levels in control subjects. After in vitro anti-CD3 stimulation, numbers of IL-4+ producing iNK T cells from subjects with coeliac disease were unchanged but increased by 21% in control subjects. In subjects with coeliac disease, Valpha24 mRNA intestinal expression was reduced to 17% (p<0.001) by relative PCR and numbers of intestinal Valpha24+ T cells were 16% (p<0.01) of levels in control subjects.

CONCLUSIONS

We conclude that Valpha24+ T cells and iNK T cells are deficient in coeliac disease. We speculate that this deficiency could contribute to the failure of immunological oral tolerance that seems to underlie this disease.

Lack of proliferative response by gluten-specific T cells in the blood and gut of patients with dermatitis herpetiformis

The majority of patients with Dermatitis Herpetiformis (DH) have a gluten-sensitive enteropathy which may be triggered by a T cell-mediated immune response to gluten. Using a proliferative assay, the responses to gluten fraction III, recall antigens and mitogens of peripheral blood mononuclear cells (PBMC) and gut T cell lines (TCL) isolated from patients with Dermatitis Herpetiformis (DH) and normal controls were studied. In most cases, neither PBMC nor gut T cell lines (which were predominantly CD3+, CD4+, TCR alpha beta +) from either controls or patients proliferated in response to gluten fraction III alone. However, the addition of 10 U/ml IL-2 to PBMC cultures containing gluten fraction III resulted in a marked increase in proliferation in 9/19 DH patients and 7/11 controls compared to IL-2 alone. Furthermore, gluten-induced upregulation of IL-2 receptor (CD25) expression was demonstrated on PBMC from 4/4 patients with DH and 2/3 controls after 7 days' culture with antigen. A similar effect by exogenous IL-2, or the same concentration of IL-4, was observed in 8/11 (P = 0.02) and 5/6 respectively DH, and 3/4 normal gut T cell lines. No difference was observed in the response of DH and control PBMC to Tetanus toxin, Candida albicans and PPD; both normal and DH gut T cell lines were unresponsive to these antigens. However, the addition of IL-2 increased the response to Candida albicans by DH gut T cell lines. Moreover, the response of DH gut T cell lines to PHA (P < 0.001), Concanavalin A and anti-CD3 were markedly reduced compared to PBMC from the same patients. These findings suggest that gluten-specific T cells present in the blood and gut of normal and DH individuals are activated by but do not proliferate in response to specific antigen.

Recovery of the small intestine in coeliac disease on a gluten-free diet: changes in intestinal permeability, small bowel morphology and T-cell activity

Intestinal permeability was assessed before and 1, 2, 4, 8 and 12 weeks after commencing a gluten-free diet (GFD) in eight coeliac subjects. Intestinal morphology was quantified in six coeliac subjects on a normal diet, six coeliac subjects on a GFD, and 21 normal subjects. T-cell activity was measured in the eight coeliac subjects by soluble interleukin-2 receptor (sIL-2R) concentration (normal less than 477 U/mL). Intestinal permeability was increased 10-fold with a geometric mean value of 0.72 on a normal diet, and decreased to 0.17 at 4 weeks (P = 0.04), to 0.07 at 8 weeks (P = 0.010), and to 0.20 at 12 weeks (P = 0.015) of a GFD. Two of the eight subjects showed a poor response to gluten withdrawal. Quantitative intestinal morphology showed no significant improvement after 3 to 6 months of a GFD. Mean +/- s.d. sIL-2R concentrations in the eight subjects were increased 5-fold higher than control values at 1400 +/- 530 U/mL on a normal diet and decreased to 750 +/- 200 U/mL after 12 weeks of a GFD (P = 0.004). We conclude that intestinal permeability improves rapidly in the majority of coeliac subjects after commencing a GFD, although some abnormal permeability and increased T-cell activity persists. This may be due to varying degrees of gluten ingestion resulting in continued immune activation.

Lymphocyte activation as measured by interleukin-2 receptor expression to gluten fraction 111 in coeliac disease

Lymphocyte activation was examined by interleukin-2 (IL-2) receptor expression on peripheral blood mononuclear cells from coeliac and control subjects. Purified T cells were incubated with gluten fraction 111 (a known toxic peptide for coeliac subjects), soyabean hydrolysate (an unrelated hydrolysed food antigen), and Concanavalin-A (Con-A, a non-specific mitogen). After 1-5 days incubation, expression of IL-2 receptors was assessed using a cellular enzyme-linked immunosorbent assay (ELISA). Gluten fraction 111 induced expression of IL-2 receptors on T lymphocytes from coeliac but not from normal subjects (P = 0.0005), whereas soyabean hydrolysate did not induce IL-2 receptor expression. Lymphocytes from both coeliac and normal subjects had similar increased IL-2 receptor expression after incubation with Con-A. Flow cytometry was also used to confirm specific expression of IL-2 receptor expression of lymphocytes from coeliac subjects. Interleukin-2 receptor expression increased from 0 to 5.4% of cultured mononuclear cells after 7 days incubation with gluten fraction III. These cells were CD3-positive and CD4-positive. We conclude that peripheral blood lymphocytes from coeliac subjects are sensitized specifically to gluten fraction III.

Susceptibility to tuberculosis in patients with coeliac disease

An increased prevalence of past tuberculosis is reported in an adult coeliac population. Of 76 adult coeliac disease patients, 6 had had a history of tuberculosis. This compared with the finding of no cases in a population of 81 patients with non-inflammatory bowel diseases, (p = 0.023), which was matched for age, sex, smoking, ethnic origin and social class. The 'expected' number of cases of tuberculosis amongst ACD patients has also been calculated based on local annual notification rates; this was 2.9. Radiological evidence of past tuberculosis was found in 13 (17%) ACD patients, compared with 4 (5%) control patients (p less than 0.05). It is postulated that the increased prevalence of past tuberculosis in ACD patients is the result of depressed cell mediated immunity and/or malnutrition.

Immunoperoxidase demonstration of the cellular composition of the normal and coeliac small bowel

Immunohistological analysis of the cellular composition of the small intestinal mucosa in a group of untreated and treated coeliac patients and non-coeliac control subjects was performed using monoclonal antibodies and an immunoperoxidase technique. A characteristic cellular distribution was observed within the normal mucosa. The intraepithelial and lamina propria compartments were occupied mainly by T suppressor/cytotoxic and T helper/inducer cells respectively. Further subdivision of lamina propria T helper/inducer cells with the Leu 8 antibody revealed that these were of the Leu 3a+ Leu 8- phenotype. Macrophages, defined by the RFD7 antibody, were seen to occupy the same microenvironment as T helper/inducer cells. T cells expressing the T cell activation antigen defined by anti-Ta1 were found with the normal lamina propria, although few cells were identified by the anti-Tac antibody. HLA-Dr antigens were expressed by stellate cells within the lamina propria, and also by the epithelial cells of the villi, but not by normal crypt epithelial cells. In untreated coeliac patients the distribution of the various cell types was essentially unchanged, although the number of these cells was markedly increased, including those which expressed the Ta1 antigen. A significant deviation from normal in the expression of HLA-DR antigens was found in the coeliac small bowel: these antigens were expressed not only on the villous epithelial cells but also on the epithelial cells of the crypts. Immunohistological findings in the treated coeliac patients were intermediate between the normal and untreated coeliac groups, and were completely normal in those patients with complete histological resolution of their disease. These results suggest that coeliac disease is accompanied by an enhanced stimulation of the normal mucosal immune response and do not imply a primary pathogenic role for the immune system in this disease.

Suppressor-cell activity in coeliac disease induced by alpha-gliadin, a dietary antigen

The wheat protein antigen alpha-gliadin, a fraction derived from gluten of molecular weight 60 000, activated suppressor cells from patients with coeliac disease but not from normal subjects or patients with Crohn's disease. Two other dietary antigens, casein and beta-lactoglobulin, failed to produce suppressor-cell activation. Since this phenomenon appears to be specific to coeliac disease, it may be of pathogenetic significance.

Cellular immunity in children with coeliac disease

The experimental evidence implicating defective cell-mediated immunity in coeliac disease, a condition where symptomatology is believed to be due to immunological reaction to wheat gluten, is often inconsistent and sometimes controversial. Studies of certain parameters of cellular immunity in four groups of pediatric patients were performed: coeliac patients on normal diet; coeliac patients consuming gluten-free diet; children with cow's milk sensitivity. In all these assays no significant differences were found between treated or untreated coeliac children, infants with milk allergy or the gastro-intestinal control groups. On the basis of this study we could find no evidence of impairment of cell-mediated immunity in coeliac children. This conclusion is compatible with the hypothesis that intestinal damage may be due to a subpopulation of lymphocytes sensitive to gluten in persons with normal immune systems. In adults where abnormalities of cell-mediated immunity have sometimes been noted, the reason could be a loss of lymphocytes from the damaged mucosa of the gastrointestinal tract following prolonged antigenic stimulation. This indicated the need for strict adherence to a gluten-free-diet.

Cellular response to alpha-gliadin in untreated coeliac disease

An improved technique for the detection of alpha-gliadin sensitised mononuclear cells in the peripheral blood of untreated coeliac patients is described. This method is a modification of the direct LMIF assay, and involves exposure of lymphocytes to alpha-gliadin and the assay of the resultant lymphokine produced using normal leucocytes as indicator cells. All untreated coeliac patients, 14 of 15 treated patients, and two of 28 controls responded to alpha-gliadin. The direct LMIF assay in comparison is less sensitive, and detected sensitivity to alpha-gliadin in only four out of eight patients with untreated coeliac disease. Use of the indirect LMIF technique demonstrates that in untreated as well as treated coeliac patients there are cells sensitised to alpha-gliadin circulating in the peripheral blood. These findings may have pathogenic and diagnostic significance.

Immunopathology of coeliac disease

Coeliac disease may be defined as a condition in which there is an abnormal jejunal mucosa with loss of villi, which improves morphologically after treatment with a gluten-free diet. Pathologically, there is damage to the jejunal enterocytes, with hyperplasia of crypt cells so that overall enteropoiesis is increased. On conventional or scanning electron microscopy the enterocytes are markedly abnormal. Histochemically, the normal punctate appearance of the lysosomes is lost and sensitive lysosomal enzyme assays on mucosal biopsy samples using isopycnic centrifugation techniques show that there is an increase in total lysosomal activity with reduction in lysosomal latency. Studies following gluten feeding in patients whose mucosa has returned to normal after treatment with a gluten-free diet show that pathological abnormalities appear within 4--8 hours of gluten challenge. Complement together with extracellular IgM can be demonstrated in the lamina propria, suggesting the formation of immune complexes. In untreated coeliac disease there is a significant reduction in serum levels of C3 and C4. There is also evidence indicating the presence of immune complexes in the serum. Coeliac disease may therefore be an intestinal model of an immune complex disease, in which an antigen derived from gluten reacts with an antibody formed locally in the gut, fixing complement and causing damage to the enterocyte by activation of lysosomes.

Skin test for coeliac disease using a subfraction of gluten

Gluten and various of its fractions and subfractions have been used for intradermal testing in 10 patients with coeliac disease and in 20 healthy control subjects. All the coeliac patients gave positive Arthus-type reactions (type III) to the subfractions of gluten, whereas all the control subjects were negative. The subfraction B2 evoked strong reactions in almost all the coeliac subjects. If tests with larger series confirm the present results, skin testing with B2 may prove to be a useful screening test for coeliac disease. As B2 has already been found to stimulate the lymphocytes of coeliac patients, the present findings are also of interest in relation to the pathogenesis of coeliac disease.

Depressed cell-mediated immunity in coeliac disease

Fourteen coeliac patients on a gluten free diet (GFD) and 10 on a normal diet were studied by lymphocyte transformation in response to PHA to assess the integrity of cell-mediated immunity (CMI). Transformation was depressed in the majority taking a normal diet, with improvement after a GFD. In some patients the depression may have been due to a serum factor, as transformation was more nearly normal when the lymphocytes were cultured in pooled AB serum than in their own serum. There was no correlation between transformation and nutritional deficiencies. Mantoux tests were performed in some of these and other coeliac patients and there was a very significant reduction in the incidence of positive tests compared with controls. These findings provide evidence of depressed CMI in coeliac patients taking a normal diet with improvement on a GFD and may be of relevance to the high risk of malignancy in coeliac disease, further strengthening the case for a strict GFD.

Cell-mediated immunity to gluten fraction III in adult coeliac disease

Peripheral blood lymphocytes were obtained from twenty-seven healthy control subjects, twenty-one coeliac patients on a gluten-free diet and fourteen patients on a normal diet. When the cells were cultured in vitro in the presence of 2 and 4 mg of gluten fraction III, there were significant increases in the mean ratios of response for lymphocytes from gluten-free coeliacs compared to healthy controls after 4, 5 and 6 days of culture, but for those on a normal diet significant increases were found only when using 4 mg of gluten on the 4th and 5th days of culture. When three further patients were changed from a normal to a gluten-free diet, the ratios of response for their lymphocytes increased. The results suggest that certain coeliacs may exhibit a weak delayed hypersensitivity reaction to gluten. Its more ready demonstration in patients on a gluten-free diet could be explained on the release of sensitized lymphocytes from the intestinal mucosa into the peripheral circulation after gluten withdrawal.

The jejunal cellular infiltrate in coeliac disease complicated by lymphoma

Lymphocytes and plasma cells in the lamina propria and lymphocyte in the epithelium have been quantitated in jejunal biopsies from 18 patients with coeliac disease who developed lymphoma. In six patients two or more serial biopsies were available for study. Counts were compared with those obtained in 15 healthy controls and 30 other coeliacs, 15 of whom have been on a gluten-free diet for more than 12 months. Results showed that although the lymphoma patients have abnormal counts compared with controls, they differed from untreated coeliacs in that they had lower plasma cell and higher lymphocyte counts in the lamina propria and lower lymphocyte counts in the epithelium. Such changes tended to be present for up to five years before the diagnosis of lymphoma was made. The results suggest that the immunological status of coeliac patients with lymphoma differs from that of other coeliacs and it could represent a primary abnormality and also be relevant to the development of lymphoma.

Autoantibodies in children with coeliac disease

Anti-reticulin antibody was found in the serum of thirty-two of forty-eight (67%) children with coeliac disease, a statistically significant difference from an incidence of seven of forty-eight matched controls. The antibody was solely of IgG class in 66% of patients and 76% of controls and in the remainder comprised a mixture of IgG and IgA. The antibody could not be absorbed with gluten. One coeliac patient had serum antinuclear factor, and one had smooth muscle antibody. No statistically significant differences in mean IgG, IgA and IgM levels were demonstrable between coeliac patients and controls, or between anti-reticulin antibody positive and negative groups. The presence of anti-reticulin antibody did not correlate with the presence of serum precipitins to a number of dietary proteins.

The enterocyte in coeliac disease

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Immunoglobulins and dietary protein antibodies in childhood coeliac disease

Twenty-four children with coeliac disease were compared with a control group, comprising 17 children with a variety of gastroenterological disorders, with respect to serum immunoglobulins and dietary protein antibodies. Elevated levels of IgA and abnormally low levels of IgM were demonstrated in one third of the coeliac patients. Antibodies to at least one of eight dietary proteins were found in 50% of coeliac children. Three children with raised levels of serum IgA and two with deficient IgM were re-examined after varying periods on a gluten-free diet. Antibodies to dietary proteins had waned and immunoglobulin levels returned to normal in all cases. The raised IgA was considered to have resulted from an extensive immunological response to antigens of dietary origin which had entered through the abnormal gut mucosa. It is suggested that IgM deficiency was due to specific inhibition of IgM synthesis by dietary components which had also entered through the mucosa.