Immunoglobulins in the jejunal mucosa in adult coeliac disease and dermatitis herpetiformis after the reintroduction of dietary gluten

Immune development and intestinal microbiota in celiac disease

Celiac disease (CD) is an immune-mediated enteropathy, triggered by dietary wheat gluten and similar proteins of barley and rye in genetically susceptible individuals. The etiology of this disorder is complex, involving both environmental and genetic factors. The major genetic risk factor for CD is represented by HLA-DQ genes, which account for approximately 40% of the genetic risk; however, only a small percentage of carriers develop the disease. Gluten is the main environmental factor responsible for the signs and symptoms of the disease, but exposure to gluten does not fully explain the manifestation of CD. Epidemiological and clinical data suggest that environmental factors other than gluten might play a role in disease development, including early feeding practices (e.g., breast milk versus formula and duration of breastfeeding), infections, and alterations in the intestinal microbiota composition. Herein, we review what is known about the influence of dietary factors, exposure to infectious agents, and intestinal microbiota composition, particularly in early life, on the risk of developing CD, as well as the possible dietary strategies to induce or increase gluten tolerance.

Antibodies in celiac disease: implications beyond diagnostics

Celiac disease is a multisystemic dietary, gluten-induced autoimmune disorder characterized by the presence of transglutaminase (TG) 2 serum autoantibodies. Distinct autoantibodies targeting members of the TG family (TG2, TG3 and TG6) are found deposited in small-bowel mucosa and in extraintestinal tissues affected by the disease. Serum autoantibodies against other self-antigens also emerge in untreated celiac disease patients. Although villous atrophy and crypt hyperplasia in small-bowel biopsy samples are still the gold standards in diagnostics, celiac disease-specific antibodies are widely used as diagnostic aids. Gluten-induced small-bowel mucosal T-cell response is the cornerstone in the pathogenesis of the disorder, but humoral immunity may also play a central role. This review article is focused on the autoantibodies that occur in the context of celiac disease. The article summarizes the diagnostic utility of different celiac-related antibodies and discusses their roles in the pathogenesis of the disease.

Usefulness of small-bowel mucosal transglutaminase-2 specific autoantibody deposits in the diagnosis and follow-up of celiac disease

BACKGROUND

Diagnosis of celiac disease may be problematic in that small-bowel villous atrophy sometimes occurs in conjunction with other enteropathies, develops gradually and may be patchy. Furthermore, as the often compromised quality of biopsy specimens renders diagnosis difficult, new diagnostic tools are warranted.

GOALS

As the celiac disease-specific autoantibodies are found deposited at their production site, in the small-bowel mucosa, they may be useful in diagnostics, especially in problematic cases. We therefore systematically assessed the occurrence of celiac-specific autoantibody deposits in a large cohort of celiac patients, and established how IgA deposits decline after initiation of a gluten-free diet.

METHODS

Transglutaminase-2 specific mucosal IgA autoantibody deposits were determined from small-bowel mucosal biopsies in 261 untreated, 71 short-term (1 y), and 105 long-term (2 to 41 y) treated celiac disease patients and in 78 nonceliac controls. The presence of the deposits was compared with celiac serology, mucosal villous morphology and density of intraepithelial lymphocytes.

RESULTS

All untreated celiac disease patients had mucosal autoantibody deposits and their intensity was moderate or strong in 90% of cases. In contrast, 18% of the controls had weak depositions. During a gluten-free diet the intensity of the deposits diminished, but was still faintly positive in 56% of long-term treated celiac patients. The efficiency of the test in determining mucosal autoantibody deposits was superior to serology and inflammatory markers.

CONCLUSIONS

Mucosal transglutaminase-2 specific autoantibody deposits proved to be accurate gluten-dependent markers of celiac disease and would thus be of value in the diagnostics and dietary monitoring of this disorder.

Decreased numbers of circulating plasmablasts and differences in IgA1-plasmablast homing to skin in coeliac disease and dermatitis herpetiformis

The two clinical phenotypes of gluten enteropathy, coeliac disease (CD) and dermatitis herpetiformis (DH), were characterized for numbers and homing profiles of circulating final effector B cells, plasmablasts, identified as immunoglobulin (Ig)-secreting cells (ISC). In CD, the numbers of ISC were approximately 50% lower than in DH or controls. ISC expressed peripheral lymph node homing receptor (HR), L-selectin, less frequently in CD (54%) and DH (52%) patients than in controls (70%). The expression of gut mucosal HR, alpha(4)beta(7), was less frequent in CD (42%) than in DH (65%) or controls (60%). In DH, but not in CD or controls, a higher proportion of IgA1-ISC (40%) than IgA2-ISC (25%) expressed the skin HR, cutaneous lymphocyte-associated antigen. In gluten enteropathy circulating plasmablasts are more mature, but decreased in number, and have distorted homing profiles. Differential IgA1-plasmablast homing could be associated with the development of skin rash with IgA1-deposits in DH but not in CD.

Proteins specifically hyperexpressed in a coeliac disease patient with aberrant T cells

An aberrant T cell population is the basis for diagnosis of refractory coeliac disease and determines the risk of enteropathy-associated T cell lymphoma. This disease is serious with a poor survival. Pathogenetic mechanisms sustaining aberrant T cell proliferation remain unknown. Recently, alemtuzumab has been proposed as a promising new approach to treat these patients. Only few single cases have been tested at present; nevertheless, in all the cases a clinical improvement was observed. However, whether intraepithelial lymphocytes have been targeted effectively by alemtuzumab is still debated. This study reports, using two-dimensional difference gel electrophoresis (2D DIGE), hyperexpressed proteins associated specifically with aberrant T cells found in a patient with coeliac disease by comparison of the protein expression of this sample with that of patients with coeliac disease and polyclonal T cells or with control subjects. The data demonstrated a significantly higher expression of IgM, apolipoprotein C-III and Charcot-Leyden crystal proteins in a duodenal biopsy specimen of the patient with clonal T cells compared with that of other patients. These preliminary results allow hypothesizing different clinical effects of alemtuzumab in patients with coeliac disease and aberrant T cell proliferation, because as well as the probable effect on T cells, alemtuzumab could exert its effect by acting on inflammatory associated CD52(+) IgM(+) B cells and eosinophil cells, known to produce IgM and Charcot-Leyden crystal proteins, that we demonstrated to be altered in this patient. The results also emphasize the possible association of apolipoprotein with aberrant T cell proliferation.

[Genetics and immunopathogenics aspects of the celiac disease: a recent vision]

BACKGROUND

Celiac disease, or gluten-sensitive enteropathy, is a strongly inherited condition. Although the genetic association of CD with the DQ2 and DQ8 HLA haplotypes has been known for long, others HLA and non-HLA genes are also important in the development of the disease. Celiac disease results of the combined effect of different normally functioning genes' products. The tissue damage in celiac disease is immunologically mediated and several effector mechanisms are responsible for the disease expression. The interplay between genetic, immunological and environmental factors explains the large spectrum of clinical, histological and serological alterations observed in the different stages of the disease development, pointing out to the polygenic nature of celiac disease.

CONCLUSION

The recent advances in the understanding of the immunopathogenesis, genetics and diagnoses of celiac disease have allowed the revision of strict concepts and previous criteria and their adequation to the new evidences, aiming a better diagnostic and orientation to celiac patients and relatives.

The humoral immune system in coeliac disease

IgA is transported into intestinal secretions to perform exclusion of luminal antigens. The prerequisites are antigen sampling by the Peyer's patch M cells, antigen processing by antigen-presenting cells, and presentation of antigenic peptides by HLA class II molecules to immunocompetent T-cells. The basis for intestinal immunity is the maturation cycle of specifically primed T and B cells from the gut-associated lymphoid tissue via mesenteric lymph nodes and peripheral blood back to the intestinal lamina propria. In coeliac disease, patients are sensitized against gluten and serum gliadin antibodies are often detected. Gliadin antibodies are also found in other gastrointestinal diseases, other disorders and in healthy individuals not carrying the coeliac disease-specific DQA/DQB alleles. On the other hand, serum reticulin and endomysium autoantibodies are both sensitive and highly disease-specific. Positivity in patients with normal jejunal morphology indicates latency of coeliac disease. These tissue autoantibodies are directed against fibroblast-derived extracellular matrix proteins. The immune system is involved in the amplification and perpetuation of the abnormalities of the intestinal mucosa in coeliac disease. The role of antibody in the pathogenesis remains unknown. The author hypothesizes gluten-triggered autoimmune mechanism to be operative.

Binding to human jejunum of serum IgA antibody from children with coeliac disease

Jejunal histology and the presence of serum IgA antibodies (JAB) binding to human jejunum in vitro were studied in 139 children with severe malabsorptive symptoms. Among 33 children with confirmed coeliac disease (ESPGAN criteria), 13 (93%) of 14 sampled before starting on a gluten-free diet had JAB, none of 21 sampled had JAB while on a gluten-free diet of long duration, and 90% of 30 sampled during gluten challenge had JAB. 53 children had severe jejunal villous atrophy (probable coeliac disease): 71% of those younger than 2 years and 94% of those aged 2-18 years had JAB during gluten intake. JAB could not be detected in 53 disease control patients (normal jejunal histology) and in 3 coeliac disease patients with selective IgA deficiency. Simultaneous determination of antigliadin (AGA) and antiendomysium (EMA) levels, and gliadin and tissue absorption studies, showed that JAB and AGA are different, whereas JAB and EMA are probably identical. IgA JAB could be the target-organ-related autoantibodies in coeliac disease.

T-cell and plasma cell populations in coeliac small intestinal mucosa in relation to dermatitis herpetiformis

Differential lymphocyte and plasma cell counts and measurements of mucosal architecture were studied in small intestinal biopsies from 17 controls and 17 patients with untreated uncomplicated coeliac disease of whom five also had dermatitis herpetiformis. Intraepithelial T-cell and plasma cell counts and measurements of mucosal architecture were not significantly different in the two coeliac groups but both groups differed from the controls. Lamina propria T-cell counts were significantly higher in the patients who also had dermatitis herpetiformis than in uncomplicated coeliac disease, with a significant increase in the Leu 2 (CD8) positive (cytotoxic/suppressor) T-cell subset. This suggests a specific abnormality of T-cell control of immune responsiveness in the pathogenesis of the skin manifestations of dermatitis herpetiformis which is not found in uncomplicated coeliac disease.

Immunoglobulin A deposition in jejunal mucosa of children with dermatitis herpetiformis

Previously we have shown by indirect immunofluorescence (IF) technique that a special IgA antibody in the sera of patients with dermatitis herpetiformis (DH) binds to the structures of the normal jejunum. Now we show by direct IF that specific IgA deposits are present in the proximal jejunum of 11/12 DH and 2/2 celiac patients before a gluten-free diet (GFD). The IgA deposition was in a tubular pattern underlying the villous and crypt epithelial basement membranes and in the lamina propria. This IgA deposition diminished or was not detectable in DH patients under a GFD for a year, and became detectable under gluten challenge in three DH patients. One patient with celiac disease and IgA deficiency, four with other intestinal diseases, and four without jejunal damage had neither jejunal IgA deposition nor circulating IgA anti-jejunal antibody. The deposition of IgA in the jejunum seemed to be correlated with the presence of IgA anti-jejunal antibody in the serum and with the presence of jejunal damage, but the degree of jejunal atrophy, the titer of the anti-jejunal antibody, and the intensity of jejunal IgA deposition in DH patient were not clearly related. Deposition of IgA in the jejunum in DH did not clearly correlate with the activity of the skin symptoms and thus may not be directly related to the pathogenesis of the skin disease of DH.

Local immunoglobulin production is different in gastritis associated with dermatitis herpetiformis and simple gastritis

The degree of inflammation and atrophy in gastric body mucosal specimens (n = 38) from 28 patients with dermatitis herpetiformis (DH) was graded histologically. Immunoglobulin (Ig) producing cells were enumerated by paired immunofluorescence staining in a 500 microns wide section area from the muscularis mucosae to the lumen (mucosal 'tissue unit'). The number of immunocytes of the three main classes (IgA, IgM, and IgG) was significantly raised with increasing degree of gastritis. All three classes were increased in specimens showing atrophy compared with those without atrophy. IgA cells predominated as in simple gastritis, but a striking difference was a marked increase of IgM cells in specimens with the most pronounced DH-associated gastritis. Relative class distribution of immunocytes within different mucosal zones showed that the percentage of IgA cells was significantly higher in the luminal than in the basal zone, whereas the contrary was true for IgG cells. IgM cells did not show any zonal preference. No relation was seen between small bowel and gastric lesions. The disproportionate increase of gastric IgM producing cells in DH might nevertheless reflect seeding of precursor cells of the secretory immune system generated in the proximal small intestine where the local IgM response is relatively pronounced.

Gluten challenge in children with dermatitis herpetiformis: a clinical, morphological and immunohistological study

Twenty one children with dermatitis herpetiformis were studied in an attempt to evaluate the response in the skin, in jejunal morphology, and in jejunal immunoglobulin containing cell counts to gluten elimination and subsequent gluten challenge. In all of the 15 patients whose jejunal biopsy was studied after the eventual gluten challenge the jejunal lesion had returned in 2.4 to 28 months. The numbers of IgA- and IgM-containing cells were similarly raised in primary and postchallenge biopsies. In the 13 patients whose skin improved during a gluten free diet and who were challenged with gluten the rash worsened and the dapsone/sulphapyridine requirement increased. The jejunal deterioration was equally marked in the six patients whose gluten challenge was stopped because of an intractable rash as it was in those who completed the preplanned challenge. The specimens of the former, however, had significantly more IgA-containing cells than specimens of the latter. The number of intraepithelial lymphocytes clearly reflected the degree of intestinal damage. IgA-containing cells proved to be the most sensitive indicator of an immune reaction taking place in the gut of these patients. Even in the two children with initially normal or nearly normal jejunal mucosa, the IgA cell counts in the jejunal lamina propria were markedly raised.

Increased concanavalin A induced suppression in treated and untreated coeliac disease

The generation of suppression by concanavalin A in peripheral blood mononuclear cells in treated and untreated coeliac subjects using an in vitro assay was found to be significantly increased when compared with controls. The response of peripheral blood mononuclear cells to the plant mitogen concanavalin A (con A) was also significantly depressed in both groups of coeliac patients. It is proposed that the depressed cell mediated immunity found in this and other studies in coeliac patients is because of increased suppression. The possible connection between these findings and the increased incidence of malignancy also found in coeliac disease is discussed.

Immunoglobulin-producing cells in jejunal mucosa of children with coeliac disease on a gluten-free diet and after gluten challenge

The jejunal Ig-producing cell populations in a group of 12 children with established coeliac disease (CD) in remission on a gluten-free diet were compared with those of a group of 10 patients in clinical relapse after gluten challenge. Quantification of the various immunocyte classes was performed by paired immunofluorescence staining in an individually defined mucosal tissue unit constituting a 6-micron-thick and 500-micron-wide block of tissue, including the mucosa at full height from the muscularis mucosae. In the treated group the percentage IgA/IgM/IgG cell ratios were, on the average, 82.6:12.9:4.5. There were no differences in these ratios or in the absolute immunocyte numbers when compared with a group of six control patients without CD. After gluten challenge the corresponding ratios were 77.2:17.2:5.6. The median cell number per mucosal tissue unit in the IgA, IgM, and IgG class was raised 2.1, 3.8 and 2.9 times, respectively. These increases were statistically significant. Moreover, there was a significant negative correlation between the time to clinical relapse and the number of IgG cells per tissue unit after challenge. This finding indicates that locally produced antibodies of the IgG class are especially involved in the pathogenesis of CD.