Tissue transglutaminase expression in celiac mucosa: an immunohistochemical study

Liver involvement in patients with coeliac disease: proof of causality using IgA/anti-TG2 colocalisation techniques

AIMS

Despite clinical evidence of liver involvement in patients with coeliac disease (CeD), there is a lack of a method to prove this association.

METHODS

Of 146 treatment-naive patients with CeD, 26 had liver dysfunction. Liver biopsies and corresponding small intestinal biopsies were obtained from these 26 patients. Multicolour immunohistochemical and immunofluorescence confocal microscopic studies were performed on paraffin-embedded tissue to detect the IgA/anti-TG2 deposits. Follow-up liver biopsies were taken after a gluten-free diet.

RESULTS

Twenty-six out of the 146 patients (17.8%) with suspected coeliac-associated liver disease on histological examination revealed irregular sinusoidal dilatation in 15 (57.6%), steatohepatitis in 4 (15.3%), non-specific chronic hepatitis in 3 (11.5%), autoimmune hepatitis in 2 (7.6%) biopsies, including cirrhosis in one of them, irregular perisinusoidal fibrosis and changes of non-cirrhotic portal fibrosis in one biopsy each (3.8%). IgA/anti-tTG deposits were observed in 22 (84.6%) liver biopsies by dual immunohistochemistry technique, and in 24 (92.3%) by confocal immunofluorescence technique and in all corresponding duodenal biopsies (100%). Overall, IgA/anti-tTG deposits showed 100% sensitivity, 77% specificity and 85% positive predictive value for establishing an association of extraintestinal pathology and CeD using archived tissues. Follow-up liver biopsies could be obtained in five patients; four of them showed not only resolution of the histological lesions but disappearance of IgA/anti-tTG co-localisation.

CONCLUSIONS

Data of the present study adds to the body of evidence that liver lesions in patients with CeD are disease related and may have been caused by a similar pathogenic mechanism that causes intestinal changes.

Immunohistochemical Expression of Antitissue Transglutaminase 2 in Tissue Injuries: An Interpretation Beyond Celiac Disease

Tissue transglutaminase 2 enzyme plays a diverse role in intracellular and extracellular functioning. Aberrant expression of anti-TG2 antibody has recently been proposed for extraintestinal identification of celiac disease (CeD), but its utility is questionable. To examine whether anti-TG2 immunohistochemical (IHC) staining can be of diagnostic value in identifying extraintestinal involvement in CeD, tissue blocks of patients with IgA nephropathies (IgAN), minimal change disease, membranous glomerulonephritis, membrano-proliferative glomerulonephritis, normal kidney, intestinal biopsies from CeD, tropical sprue, nonspecific duodenitis, and inflammatory bowel disease; liver biopsies from patients with chronic hepatitis B and C, acute liver failure (ALF), and CeD-associated liver diseases were retrieved and subjected to IHC staining for anti-tissue transglutaminase 2 enzyme. H-score was calculated by multiplying the area of positivity and stain intensity. Anti-TG2 stain H-scores were almost similar in IgAN and non-IgANs (H-score 6.31±3 vs. 7.03±2.7); however, H-scores in both of these groups were significantly higher than in normal renal parenchyma (1.6±1.5). Only 6.2% patients with IgAN with anti-TG2 immunostain positivity showed a positive anti-tTG antibody serology and villous abnormalities, suggestive of CeD. Intestinal biopsies from patients with CeD, tropical sprue, nonspecific duodenitis, and inflammatory bowel disease also showed high anti-TG2 H-scores, with no statistically significant differences. Liver biopsies from patients with both ALF, as well as chronic liver diseases showed high anti-TG2 H-scores; with highest stain expression in ALF. In conclusion, IHC expression of anti-TG2 stain correlates with both acute and chronic tissue injuries, irrespective of etiology and organ involvement. It is not a reliable marker for diagnosis of CeD.

Younger age at diagnosis predisposes to mucosal recovery in celiac disease on a gluten-free diet: A meta-analysis

BACKGROUND AND AIMS

Persistent intestinal damage is associated with higher complication rates in celiac disease. We aimed to assess the potential modifiers of mucosal recovery.

MATERIALS AND METHODS

We screened databases (PubMed, Embase, Cochrane Trials, and Web of Science) for papers on celiac disease. Papers discussing (1) celiac patients (2) follow-up biopsy and (3) mucosal recovery after commencement of a gluten-free diet were included. The primary outcome was to produce a comprehensive analysis of complete mucosal recovery (i.e., Marsh 0 on follow-up). We compared children's recovery ratios to those of adults. Patients following a strict gluten-free dietary regimen were included in a subgroup. Summary point estimates, 95% confidence intervals (CIs), and 95% predictive intervals (PIs) were calculated. Heterogeneity was tested with I2-statistic. The PROSPERO registration number is CRD42016053482.

RESULTS

The overall complete mucosal recovery ratio, calculated from 37 observational studies, was 0.36 (CI: 0.28-0.44, PI: -0.12-0.84; I2: 98.4%, p<0.01). Children showed higher complete mucosal recovery ratio than adults (p<0.01): 0.65 (CI: 0.44-0.85, PI: -0.10-1.39; I2: 96.5%, p<0.01) as opposed to 0.24 (CI: 0.15-0.33, PI: -0.19-1.08; I2: 96.3%, p<0.01). In the strict dietary adherence subgroup, complete mucosal recovery ratio was 0.47 (CI: 0.24-0.70, PI: -0.47-1.41; I2: 98.8%, p<0.001). On meta-regression, diagnostic villous atrophy (Marsh 3) ratio (-8.97, p<0.01) and male ratio (+6.04, p<0.01) proved to be a significant determinant of complete mucosal recovery, unlike duration of gluten-free diet (+0.01, p = 0.62). The correlation between complete mucosal recovery ratio and age on diagnosis is of borderline significance (-0.03, p = 0.05).

CONCLUSIONS

There is considerable heterogeneity across studies concerning complete mucosal recovery ratios achieved by a gluten-free diet in celiac disease. Several celiac patients fail to achieve complete mucosal recovery even if a strict dietary regimen is followed. Younger age on diagnosis, less severe initial histologic damage and male gender predispose for achieving mucosal recovery.

Celiac disease: Autoimmunity in response to food antigen

Celiac disease (CD) is an increasingly common disease of the small intestine that occurs in genetically susceptible subjects by ingestion of cereal gluten proteins. Gluten is highly abundant in the modern diet and well tolerated by most individuals. In CD, however, an erroneous but highly specific, adaptive immune response is mounted toward certain parts of the gluten proteome. The resulting intestinal destruction is reversible and resolved upon removal of gluten from the diet. Post-translational modification (deamidation) of gluten peptides by transglutaminase 2 (TG2) is essential for the peptides to act as HLA-DQ-restricted T-cell antigens. Characteristically, deamidated gluten and the self-protein TG2 both become targets of highly disease specific B-cell responses. These antibodies share several peculiar characteristics despite being directed against vastly different antigens, which suggests a common mechanism of development. Importantly, no clear function has been ascribed to the antibodies and their contribution to disease may relate to their function as antigen receptors of the B cells rather than as soluble immunoglobulins. Adaptive immunity against gluten and TG2 appears not to be sufficient for establishment of the disease lesion, and it has been suggested that stress responses in the intestinal epithelium are essential for the development of full-blown disease and tissue damage. In this review we will summarize current concepts of the immune pathology of CD with particular focus on recent advances in our understanding of disease specific B-cell responses.

Gliadin intake alters the small intestinal mucosa in indomethacin-treated HLA-DQ8 transgenic mice

Celiac disease (CD) is an enteropathy caused by the ingestion of wheat gluten in genetically susceptible individuals. A complete understanding of the pathogenic mechanisms in CD has been hindered because of the lack of adequate in vivo models. In the present study, we explored the events after the intragastric administration of gliadin and of the albumin/globulin fraction from wheat in human leukocyte antigen-DQ8 transgenic mice (DQ8 mice) treated with indomethacin, an inhibitor of cyclooxygenases (COXs). After 10 days of treatment, mice showed a significant reduction of villus height, increased crypt depth, increased number of lamina propria-activated macrophages, and high basal interferon-γ secretion in mesenteric lymph nodes, all of which were specifically related to gliadin intake, whereas the albumin/globulin fraction of wheat was unable to induce similar changes. Cotreatment with NS-398, a specific inhibitor of COX-2, also induced the intestinal lesion. Enteropathy onset was further characterized by high levels of oxidative stress markers, similar to CD. Biochemical assessment of the small intestine revealed the specific activation of matrix metalloproteinases 2 and 9, high caspase-3 activity, and a significant increase of tissue transglutaminase protein levels associated with the intestinal lesion. Notably, after 30 days of treatment, enteropathic mice developed serum antibodies toward gliadin (IgA) and tissue transglutaminase (IgG). We concluded that gliadin intake in combination with COX inhibition caused a basal inflammatory status and an oxidative stress condition in the small intestine of DQ8 mice, thus triggering the mucosal lesion and, subsequently, an antigen-specific immunity.

Utility of tissue transglutaminase immunohistochemistry in pediatric duodenal biopsies: patterns of expression and role in celiac disease-a clinicopathologic review

Tissue transglutaminase (tTG) is a ubiquitous multifunctional protein. It has roles in various cellular processes. tTG is a major target of autoantibodies in celiac disease, and its expression by immunohistochemistry in pediatric celiac disease has not been fully examined. We studied tTG expression in 78 pediatric duodenal biopsies by utilizing an antibody to transglutaminase 2. Serum tTG was positive in all celiac cases evaluated. Serum antiserum endomysial antibody (EMA) and tTG were negative in all control subjects and in inflammatory bowel disease and eosinophilic gastroenteritis. There was a statistically significant difference between cases of celiac disease and normal controls in terms of tTG immunohistochemical staining in duodenal biopsies surface epithelium (P value = 0.0012). There was no significant statistical difference in terms of staining of the villous surface or crypt between the cases of celiac disease and cases with IBD (P value = 0.5970 and 0.5227, resp.). There was no detected correlation between serum tTG values and immunohistochemical positivity on duodenal biopsy in cases of celiac disease (P value = 1). There was no relationship between Marsh classification and positivity of villous surface for tTG (P value = 0.4955). We conclude that tTG has limited utility in diagnosis of celiac disease in pediatric duodenal biopsies.

Immunological indicators of coeliac disease activity are not altered by long-term oats challenge

Coeliac disease is a gluten-sensitive enteropathy that develops in genetically susceptible individuals. The disease exhibits many features of an autoimmune disorder. These include the production of highly specific anti-endomysial autoantibodies directed against the enzyme tissue transglutaminase. It is well accepted that wheat-, barley- and rye-based foods should be excluded in the gluten-free diet. Although several studies report that oats ingestion is safe in this diet, the potential toxicity of oats remains controversial. In the current study, 46 coeliac patients ingested oats for 1 year and were investigated for a potential immunogenic or toxic effect. Stringent clinical monitoring of these patients was performed and none experienced adverse effects, despite ingestion of a mean of 286 g of oats each week. Routine histological analysis of intestinal biopsies showed improvement or no change in 95% of the samples examined. Furthermore, tissue transglutaminase expression in biopsy samples, determined quantitatively using the IN Cell Analyzer, was unchanged. Employing immunohistochemistry, oats ingestion was not associated with changes in intraepithelial lymphocyte numbers or with enterocyte proliferation as assessed by Ki-67 staining. Finally, despite the potential for tissue transglutaminase to interact with oats, neither endomysial nor tissue transglutaminase antibodies were generated in any of the patients throughout the study. To conclude, this study reaffirms the lack of oats immunogenicity and toxicity to coeliac patients. It also suggests that the antigenic stimulus caused by wheat exposure differs fundamentally from that caused by oats.

The function of tissue transglutaminase in celiac disease

Celiac disease is a chronic small bowel disorder caused by an abnormal immune response to an array of epitopes of wheat gluten and related proteins of rye and barley in genetically susceptible individuals who express the HLA-DQ2/-DQ8 haplotype. Gluten peptides are efficiently presented by celiac disease-specific HLA-DQ2- and HLA-DQ8-positive antigen presenting cells to CD4(+) T-cells that, once activated, drive a T helper cell type 1 response leading to the development of the typical celiac lesion-villous atrophy, crypt hyperplasia and intraepithelial and lamina propria infiltration of inflammatory cells. Tissue transglutaminase (tTG) is a calcium dependent ubiquitous enzyme which catalyses posttranslational modification of proteins and is released from cells during inflammation. tTG is suggested to exert at least two crucial roles in celiac disease: as a deamidating enzyme, that can enhance the immunostimulatory effect of gluten, and as a target autoantigen in the immune response. Since glutamine-rich gliadin peptides are excellent substrates for tTG, and the resulting deamidated and thus negatively charged peptides have much higher affinity for the HLA-DQ2 and HLA-DQ8 molecules, the action of tTG is believed to be a key step in the pathogenesis of celiac disease. This review is focused on the function of tTG in celiac disease, although it also deals with novel advances in tTG-based therapies.

Epidermal growth factor receptor inhibition augments the expression of MHC class I and II genes

PURPOSE

Diverse immune-related effects occur with the use of epidermal growth factor receptor inhibitors (EGFRI). In addition to the cutaneous inflammation induced by EGFRIs, these agents have been associated with the exacerbation of autoimmune skin disease and contact hypersensitivity, antiviral effects, and fatal alveolar damage in the setting of lung transplantation. Because EGFR ligands can modulate MHC class I (MHCI) and II (MHCII) molecule expression, we hypothesized that some of the immune-related effects of EGFRIs are due to direct effects on the expression of MHCI and/or MHCII molecules.

EXPERIMENTAL DESIGN

Primary human keratinocytes and a malignant keratinocyte cell line (A431) were treated with EGFRIs alone or prior to IFN-γ, a potent inducer of MHCI and MHCII molecule expression. CIITA, MHCI, and MHCII RNA expression was measured using quantitative real-time reverse transcriptase PCR, and cell surface MHCI and MHCII protein expression was measured using flow cytometry. Skin biopsies from patients were analyzed for MHCI and MHCII protein expression before and during therapy with an EGFRI using immunohistochemistry.

RESULTS

Both EGFR tyrosine kinase inhibitors and ligand-blocking antibodies (cetuximab) augmented the induction of MHCI and MHCII molecules by IFN-γ in primary and malignant human keratinocytes. Unexpectedly, the increase in MHCI protein expression did not require the presence of IFN-γ. Consistent with these in vitro findings, skin biopsies from cancer patients exhibited increased epidermal MHCI protein expression during therapy with an EGFRI as well as increases in MHCI and MHCII molecule RNA.

CONCLUSIONS

These studies suggest that EGFRIs may influence immune/inflammatory responses by directly modulating MHC expression. Clin Cancer Res; 17(13); 4400-13. ©2011 AACR.