Antiendomysial antibody detection in fecal supernatants: in vivo proof that small bowel mucosa is the site of antiendomysial antibody production

Review article: Faecal biomarkers for assessing small intestinal damage in coeliac disease and environmental enteropathy

BACKGROUND

In coeliac disease and environmental enteropathy, dietary gluten and enteric infections cause reversible inflammation and morphological changes to the small intestinal mucosa that can be detected in biopsy samples obtained by endoscopy. However, there is a clear need for non-invasive biomarkers. Constant shedding of mucosal material into the bowel lumen and faeces, together with easy availability of stool, makes it an interesting sample matrix.

AIMS

To conduct a systematic literature search and summarize the existing evidence for host mucosa-derived faecal biomarkers in evaluating small intestinal damage.

METHODS

We searched for studies on PubMed (MEDLINE) until 1 March 2024.

RESULTS

We identified 494 studies and included 35 original case-control and cohort studies. These assessed host mucosal transcripts and 14 other markers aiming specifically to reflect inflammation and cell-mediated, innate and gluten-induced immune responses. In coeliac disease, faecal calprotectin and anti-gliadin, tissue transglutaminase, endomysium and deamidated gliadin peptide antibodies were the most studied but with inconsistent results. Single studies reported positive findings about microRNA transcripts, β-defensin-2, lipocalin-2, zonulin-related proteins and angiotensin-converting enzyme. In environmental enteropathy, a non-significant association was reported between calprotectin and urine lactulose/mannitol ratio; there were conflicting results for neopterin, myeloperoxidase and host transcripts. Single studies reported a positive association for lactoferrin, and a negative association for regenerating islet-derived protein 1. Studies comparing faecal markers against small intestinal biopsy findings were not identified in environmental enteropathy.

CONCLUSIONS

Further studies are needed to determine reliable faecal markers as a proxy for small intestinal mucosal damage.

Intestinal anti-tissue transglutaminase IgA deposits as a complementary method for the diagnostic evaluation of celiac disease in patients with low-grade histological lesions

Evaluating the usefulness of intestinal anti-transglutaminase IgA (anti-TG2 IgA) deposits detection as a complementary or decision-supporting tool in the diagnosis of celiac disease (CD) in patients with low degree of enteropathy. Small intestinal biopsies (SIB) were performed from 2008 to 2017 in patients on suspicion of CD (positive CD serology and/or symptoms) referred to our Pediatric Gastroenterology Unit. We determined anti-TG2 IgA deposits by using double immunofluorescence in all the patients in whom Marsh 0 or Marsh1 was detected in the conventional histological study and in a random selection of patients with clearly positive serology and histological Marsh 2-3 lesion. 75 pediatric patients were split into 3 groups according to the final diagnosis: 1) 13 children with a Marsh 0 or 1, negative CD serology and final non-CD diagnosis;none presented intestinal anti-TG2 IgA deposits; 2) 15 potential CD cases (Marsh 0 or 1 and CD-associated antibodies), detecting anti-TG2 IgA deposits in 12; on follow-up, another biopsy performed in 11/15 showed villi atrophy in 7 and a Marsh 2 lesion in two of them, patients being finally diagnosed as CD cases; and 3) 47 children with Marsh 2-3 histological lesion and final CD diagnosis; all of them had intestinal anti-TG2 IgA deposits. Anti-TG2 deposits are a useful complementary tool for CD diagnosis in pediatric population with digestive pathologies suggestive of CD. It is especially helpful in those with low grade lesion, in which anti-TG2 deposits are predictive of the development of more severe lesions on follow-up.

Diagnosing and Monitoring Celiac Patients with Selective IgA Deficiency: Still an Open Issue

Although, the association between celiac disease (CD) and selective immunoglobulin A deficiency (SIgAD) has been known for more than fifty years, the procedures for diagnosing and monitoring patients with both conditions are still far from definitive. When serological markers were introduced as pre-bioptic investigations, it was immediately clear that searching for specific IgA antibodies without checking total serum IgA could lead to a failure in diagnosing IgA-deficient CD patients, while specific IgG antibodies could be useful as additional tests, because they are frequently found in the serum of affected patients. Nonetheless, until recently the diagnosis of CD in IgA-deficient patients was based on the few, fragmentary and often contradictory data available in literature. The introduction of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) guidelines in 2012 provided the current criteria for diagnosing CD in IgA-deficient patients, although some issues remained open, such as the selection of patients who should undergo specific IgG antibody testing and the choice of the most reliable IgG-based test for both diagnosis and follow-up. A real-life study recently assessed the impact of the 2012 ESPGHAN guidelines in diagnosing and monitoring CD in SIgAD patients, highlighting several pitfalls that can lead to operational uncertainties and difficulties in patient management. In the present report, the evolution of diagnostic tools and criteria for CD in SIgAD patients has been critically assessed, both strengths and open issues have been highlighted, and future perspectives for improving the current diagnostic protocols have been suggested.

Intestinal Anti-tissue Transglutaminase2 Autoantibodies: Pathogenic and Clinical Implications for Celiac Disease

Celiac disease (CD) is a systemic disease that primarily affects the small intestine. The presence of anti-tissue transglutaminase 2 (anti-TG2) antibodies in the serum, as well as the presence of autoimmune phenomena, account for the inclusion of CD among autoimmune diseases. Anti-TG2 autoantibodies are produced at intestinal level, where they are deposited even before they appear in circulation. The pathogenic events that lead to their production are still not completely defined, but a central role seems to be played by gliadin-specific T cells. Interestingly, limited somatic mutations have been observed in VH and VL genes in TG2-specific plasma cells, another important aspect being the biased use of a heavy chain encoded by the VH5 gene. Conflicting data have been produced over the years on the effect of anti-TG2 antibodies on TG2 function. Although the presence of anti-TG2 antibodies in serum is considered a hallmark of CD and relevant from a clinical viewpoint, the role of these autoantibodies in the development of the celiac lesion remains to be defined. In the years, different technical approaches have been implemented to detect and measure intestinal CD-associated autoantibody production. Two aspects can make intestinal anti-TG2 antibodies relevant: from a clinical viewpoint: the first is their proposed ability in potential coeliac patients to predict the development of a full-blown enteropathy; the second is their possible role in revealing a condition of reactivity to gluten in patients with no circulating CD-associated autoantibodies. In fact, the detection of CD-specific autoantibodies production in the intestine, in the absence of serum positivity for the same antibodies, could be suggestive of a very early condition of gluten reactivity; alternatively, it could be not specific for CD and merely attributable to intestinal inflammation. In conclusion, the role of mucosal anti-TG2 antibodies in pathogenesis of CD is unknown. Their presence, the modalities of their production, their gluten dependence render them a unique model to study autoimmunity.

Progress in the serology-based diagnosis and management of adult celiac disease

Introduction: This article provides a comprehensive overview of the development and application of serological tests used routinely in clinical practice for the diagnosis and management of adult celiac disease.Areas covered: We summarize existing scientific literature related to anti-endomyseal, anti-tissue transglutaminase, and anti-deamidated gliadin peptide antibodies and detail the current and potential future applications of these tests in celiac disease.Expert commentary: Current serological tests in celiac disease have some of the best performance characteristics among disease-specific tests. However, in adult celiac disease, current diagnostic algorithms still rely on duodenal biopsies to confirm the diagnosis. A 'biopsy avoidance strategy' has been implemented in pediatric celiac disease. Future high-quality studies will help inform on whether this approach can be implemented into adult gastroenterology services. It is envisaged that the next 5 years will see an increasing reliance on serology in the diagnosis of adult celiac disease.

Laboratory tests commonly used in complementary and alternative medicine: a review of the evidence

It is increasingly easy for the general public to access a wide range of laboratory tests. Tests can be ordered online with little or no input from a health professional. The complementary and alternative medicine (CAM) community promote and sell a wide range of tests, many of which are of dubious clinical significance. Many have little or no clinical utility and have been widely discredited, whilst others are established tests that are used for unvalidated purposes. They range from the highly complex, employing state of the art technology, e.g. heavy metal analysis using inductively coupled plasma-mass spectrometry, to the rudimentary, e.g. live blood cell analysis. Results of 'CAM tests' are often accompanied by extensive clinical interpretations which may recommend, or be used to justify, unnecessary or harmful treatments. There are now a small number of laboratories across the globe that specialize in CAM testing. Some CAM laboratories operate completely outside of any accreditation programme whilst others are fully accredited to the standard of established clinical laboratories. In this review, we explore CAM testing in the United States, the United Kingdom and Australia with a focus on the common tests on offer, how they are reported, the evidence base for their clinical application and the regulations governing their use. We will also review proposed changed to in-vitro diagnostic device regulations and how these might impact on CAM testing.

Gluten-related disorders: certainties, questions and doubts

In the last decade, the ingestion of gluten, a heterogeneous complex of proteins present in wheat, rice, barley and probably in oats, has been associated with clinical disorders, such as celiac disease, wheat allergy and recently to non-celiac gluten sensitivity or wheat intolerance syndrome. Gluten-related disorders, which are becoming epidemiologically relevant with an estimated global prevalence of about 5%, require the exclusion of gluten from the diet. For the past 5 years, an important shift in the availability of gluten-free products, together with increased consumption in the general population, has been recorded and is estimated to be about 12-25%. Many people follow a self-prescribed gluten-free diet, despite the fact that the majority have not first been previously excluded, or confirmed, as having gluten disorders. They rely on claims that a gluten-free diet improves general health. In this review, we provide an overview of the clinical disorders related to gluten or wheat ingestion, pointing out the current certainties, open questions, possible answers and several doubts in the management of these conditions. KEY MESSAGE Incidence of gluten-related disorders is increased in the last decade and self-diagnosis is frequent with inappropriate starting of a gluten-free diet. Gluten and wheat are considered as the most important triggers to coeliac disease, wheat allergy and non-celiac gluten sensitivity. Pediatricians, allergologist and gastroenterologist are involved in the management of these conditions and appropriate diagnostic protocols are required.

Extension of the celiac intestinal antibody (CIA) pattern through eight antibody assessments in fecal supernatants from patients with celiac disease

BACKGROUND

Detection of anti-transglutaminase, anti-endomysium and anti-gliadin antibodies is commonly used to screen celiac disease patients. Besides that in serum, these antibodies are detectable in culture supernatants of oral, duodenal and colonic biopsy samples, saliva, gut lavage fluid samples, and fecal supernatants. Our aim was to extend the intestinal antibody pattern in fecal supernatants from patients with celiac disease.

METHODS

The fecal supernatants obtained from 25 celiac disease patients and 12 healthy volunteers were used to determine IgA and IgG1 anti-endomysium by immunofluorescence analysis, IgA and IgG anti-transglutaminase, IgA and IgG anti-deamidated gliadin peptides, IgA/IgG anti-transglutaminase/deamidated gliadin peptides and IgA anti-actin by enzyme-linked immunosorbent assay.

RESULTS

IgA anti-endomysium were found in 11 of 25 (44.0%) celiac disease patients and in none of healthy volunteers (p=0.0066). The levels of IgA anti-transglutaminase, IgA anti-deamidated gliadin peptides, IgA/IgG anti-transglutaminase/deamidated gliadin peptides and IgA anti-actin determined in celiac disease patients were significantly higher (p=0.0005, p=0.0018, p=0.0061 and p=0.0477, respectively) than those measured in healthy volunteers. The ROC curve analysis showed a diagnostic significance in IgA anti-transglutaminase (AUC=0.862, p<0.0001), IgA anti-deamidated gliadin peptides (AUC=0.822, p<0.0001) and IgA/IgG anti-transglutaminase/deamidated gliadin peptides (AUC=0.783, p=0.0003) fecal tests.

CONCLUSIONS

Our data extend the intestinal antibody pattern detectable in fecal supernatants, thus increasing the knowledge in the humoral immunity of celiac disease. Further studies are needed to better evaluate the role of fecal antibody tests in identifying celiac disease patients.

Intestinal titres of anti-tissue transglutaminase 2 antibodies correlate positively with mucosal damage degree and inversely with gluten-free diet duration in coeliac disease

It has always been known that anti-tissue transglutaminase 2 (anti-TG2) antibodies are produced in the small intestine. Their serum titres correlate with mucosal damage degree and decrease on a gluten-free diet (GFD). We aimed to correlate intestinal anti-TG2 antibodies levels with degree of mucosal damage and GFD duration. Thirty-four active, 71 potential and 24 CD patients on GFD for at least 2 years were enrolled. Anti-TG2 deposits were detected in intestinal biopsies by double immunofluorescence. Biopsies were cultured for 24 h with medium, and with gliadin peptic tryptic digest (PTG) or A-gliadin peptide 31-43 (P31-43). Anti-TG2 antibodies secreted into supernatants were measured by enzyme-linked immunosorbent assay (ELISA). All active CD patients secreted high titres of anti-TG2 antibodies into culture medium that increased with the worsening of mucosal injury (Spearman's r = 0·71; P < 0·0001). Seventy of 71 potential CD patients and 15 of 24 treated CD patients secreted low titres of anti-TG2 antibodies into supernatants, eight of nine negative treated patients being on GFD for more than 10 years. An inverse correlation between antibody titres and duration of GFD was found, (Spearman's r = -0·52; P < 0·01). All active, 53 of 71 potential and six of 24 treated, CD patients showed anti-TG2 mucosal deposits. Five of six positive treated CD patients had been on GFD for fewer than 6 years and were also positive for secreted anti-TG2. In treated patients, PTG/P31-43 was not able to induce secretion of anti-TG2 antibodies into culture medium. Measurement of anti-TG2 antibodies in biopsy supernatants proved to be more sensitive than detection by immunofluorescence to reveal their intestinal production. Intestinal antiTG2 antibodies titres correlated positively with the degree of mucosal damage and inversely with the duration of GFD.

Intestinal anti-tissue transglutaminase antibodies in potential coeliac disease

Anti-tissue transglutaminase 2 (anti-TG2) antibodies are present in the serum of the great majority of untreated coeliac disease (CD) patients. They are produced and deposited in the small intestinal mucosa. Potential CD patients present serum anti-TG2 antibodies higher than cut-off, but a normal duodenal mucosa where mucosal deposits of anti-TG2 are not always detectable. The aim of our work was to investigate the presence of anti-TG2 intestinal antibodies in patients with potential CD, and identify the most sensitive test to detect them. Twelve active CD patients, 28 potential CD patients and 39 non-CD controls were enrolled. Biopsy fragments from all patients were analysed by double immunofluorescence to detect mucosal deposits of anti-TG2 antibodies. Fragments from the same subjects were also cultured for 24 h with medium in the presence or absence of gliadin peptides. Anti-TG2 autoantibodies secreted into supernatants were measured by enzyme-linked immunosorbent assay. All active CD, 68% of potential CD patients and 20% of non-CD controls showed mucosal deposits of immunoglobulin (Ig)A anti-TG2; at the same time 100, 96 and 8% of active CD, potential CD and non-CD control patients secreted these antibodies in culture supernatants, respectively. Our data showed that, to detect intestinal anti-TG2 antibodies, the measurement of antibodies secreted into culture supernatants has higher sensitivity and specificity (97·5 and 92·3%, respectively) than the detection of mucosal deposits (77·5 and 80·0%, respectively). The measurement of intestinal anti-TG2 antibodies may prove useful in clinical practice to predict evolution towards mucosal atrophy in potential coeliac patients and identify patients with gluten sensitivity.

Majority of children with type 1 diabetes produce and deposit anti-tissue transglutaminase antibodies in the small intestine

OBJECTIVE

Anti-tissue transglutaminase (TG2) antibodies are the serological marker of celiac disease. Given the close association between celiac disease and type 1 diabetes, we investigated the production and deposition of anti-TG2 antibodies in the jejunal mucosa of type 1 diabetic children.

RESEARCH DESIGN AND METHODS

Intestinal biopsies were performed in 33 type 1 diabetic patients with a normal mucosal architecture: 14 had high levels (potential celiac disease patients) and 19 had normal levels of serum anti-TG2 antibodies. All biopsy specimens were investigated for intestinal deposits of IgA anti-TG2 antibodies by double immunofluorescence. In addition, an antibody analysis using the phage display technique was performed on the intestinal biopsy specimens from seven type 1 diabetic patients, of whom four had elevated and three had normal levels of serum anti-TG2 antibodies.

RESULTS

Immunofluorescence studies showed that 11 of 14 type 1 diabetic children with elevated levels and 11 of 19 with normal serum levels of anti-TG2 antibodies presented with mucosal deposits of such autoantibodies. The phage display analysis technique confirmed the intestinal production of the anti-TG2 antibodies; however, whereas the serum-positive type 1 diabetic patients showed a preferential use of the VH5 antibody gene family, in the serum-negative patients the anti-TG2 antibodies belonged to the VH1 and VH3 families, with a preferential use of the latter.

CONCLUSIONS

Our findings demonstrate that there is intestinal production and deposition of anti-TG2 antibodies in the jejunal mucosa of the majority of type 1 diabetic patients. However, only those with elevated serum levels of anti-TG2 antibodies showed the VH usage that is typical of the anti-TG2 antibodies that are produced in patients with celiac disease.

Detection of anti-endomysial and anti-tissue transglutaminase autoantibodies in media following culture of oral biopsies from patients with untreated coeliac disease

BACKGROUND AND AIMS

Coeliac disease is an autoimmune disorder characterised by high levels of anti-endomysial and anti-tissue transglutaminase autoantibodies in sera and media of cultured intestinal mucosa biopsies from affected patients. In this study, we wished to investigate whether anti-endomysial and anti-tissue transglutaminase antibodies can also be detected in culture media of oral mucosa specimens, and whether the mouth can be used as an area of immunological testing for coeliac disease.

METHODS

Small intestine and cheek biopsy samples taken from 16 patients with active coeliac disease and from 11 controls were cultured in vitro for 48 h at 37 degrees C in presence of medium alone. Anti-endomysial and anti-tissue transglutaminase were detected in sera and in supernatants of these cultured biopsy samples by indirect immunofluorescence and enzyme immunoassay (EIA), respectively.

RESULTS

Anti-endomysial and anti-tissue transglutaminase were positive in sera of 15/16 coeliac disease patients. Culture media of intestinal mucosa samples from 14/16 coeliac disease patients were anti-endomysial positive, while the same antibodies were positive in supernatants of cultured oral mucosa samples from 15/16 coeliac disease patients. Anti-tissue transglutaminase were positive in both intestinal and oral culture media of 15/16 coeliac disease patients. Neither anti-endomysial nor anti-tissue transglutaminase were found in sera or in culture supernatants of both intestinal and oral biopsy samples from 11 controls.

CONCLUSIONS

Our study suggests a new immunological site to detect the pathognomonic autoantibodies of coeliac disease and confirms that the mouth is involved in this illness.

Longitudinal follow-up examination of antigliadin antibody positive children and adults

BACKGROUND

We previously investigated the prevalence of asymptomatic celiac disease in 3004 healthy children and 4313 adult blood donors by screening for IgA and IgG class antigliadin antibodies (AGA) and IgA class anti-endomysial antibodies (EmA). In none of the 162 exclusive AGA-positive adults and in only one of the 117 exclusive AGA-positive children could celiac disease be diagnosed. We followed up AGA-positive individuals in respect of the significance of the AGA.

METHODS

All AGA-positive children and adults were invited for a follow-up clinical examination and laboratory investigations including AGA-IgA, AGA-IgG and EmA. Celiac disease-specific antibodies were also determined in stool samples.

RESULTS

Sixty-nine adults and 47 children returned for follow-up. In 26 (37.7%) cases of the 69 adults formerly tested AGA-positive, AGA were still detectable after an average period of 3.7 years. In 21 (44.7%) cases of 47 formerly AGA-positive children, AGA were still detectable after an average period of 4.3 years. None of the 69 adults and 47 children showed seroconversion to EmA. There were no significant abnormalities in the laboratory results or any clinical signs of enteropathy. The appearance of fecal and serum antibodies was compared in 112 subjects but no correlation between fecal and serum antigliadin antibodies was found.

CONCLUSIONS

In both studied populations of adults and children, AGA disappeared in more than 50% of the cases. The appearance of AGA has to be interpreted as a non-specific immunomodulation phenomenon, confirming the low specificity of AGA as a serologic marker for celiac disease.

Detection of secretory IgA antibodies against gliadin and human tissue transglutaminase in stool to screen for coeliac disease in children: validation study

OBJECTIVE

To evaluate two commercial stool tests for detection of secretory IgA antibodies against gliadin and human tissue transglutaminase for diagnosis of coeliac disease in children with symptoms.

SETTING

Tertiary care children's hospital.

PARTICIPANTS

Coded stool samples from 20 children with newly diagnosed coeliac disease and 64 controls. Six children with coeliac disease had stool tests every two weeks for three months after starting a gluten-free diet.

MAIN OUTCOME MEASURES

Secretory IgA antibodies against gliadin and human tissue transglutaminase in stool samples, determined in duplicate by using recommended cut-off limits.

RESULTS

Sensitivity of faecal antibodies against human tissue transglutaminase was 10% (95% confidence interval 1% to 32%), and specificity was 98% (91% to 100%). For antibodies against gliadin, sensitivity was 6% (0% to 29%) and specificity was 97% (89% to 100%). Optimisation of cut-off limits by receiver operating characteristic analysis and use of results of both tests increased sensitivity to 82%, but specificity decreased to 58%. All follow-up stool tests remained negative, except for two positive anti-gliadin results in one patient, six and 10 weeks after the gluten-free diet was started.

CONCLUSIONS

Neither stool test was suitable for screening for coeliac disease in children with symptoms.

Diagnosis of coeliac disease

The diagnosis of coeliac disease depends on the finding of characteristic, though not specific changes, of intraepithelial lymphocytosis, crypt hyperplasia and various degrees of villous height reduction identified in duodenal biopsies of individuals ingesting a gluten containing diet, together with symptomatic and histologic improvement on gluten withdrawal. Serologic testing has become the main mode of determining who will undergo biopsy. The IgA endomysial antibody and IgA tissue transglutaminase antibody have approximately 90% sensitivity and specificity, though there are reports of lower sensitivity and specificity in the clinical practice setting. This is due to lower titers of these antibodies in the presence of lesser degrees of mucosal damage. The widespread availability of serologic tests for coeliac disease allows the diagnosis to be considered by any physician. Gastroenterologists will be required to interpret the results of serologic tests and perform duodenal biopsies when indicated. Pathologists likewise need to be better acquainted with the more subtle changes of cell mediated immunity within the mucosa that are suggestive of underlying gluten sensitivity.

Anti-tissue transglutaminase antibodies in inflammatory bowel disease: new evidence

Anti-tissue transglutaminase, previously held to be identical to anti-endomysial antibodies in celiac sprue, has been reported in inflammatory bowel disease patients. To investigate these data further, we evaluated serum and intestinal anti-tissue transglutaminase in inflammatory bowel disease patients, with respect to the Crohn’s disease activity index and the integrated disease activity index. Study population comprised: 49 patients with Crohn’s disease and 29 patients with ulcerative colitis; 45 patients with celiac sprue and 85 autoimmune patients as disease controls; and 58 volunteers as healthy controls. Immunoglobulin A (IgA) anti-recombinant human tissue transglutaminase and anti-endomysial antibody detection in sera and fecal supernatants were performed. Adsorption of positive sera with recombinant human tissue transglutaminase were also performed. Marked increased anti-tissue transglutaminase concentrations were found in celiac sprue, while low-positive values were also found in Crohn’s disease and ulcerative colitis. Anti-endomysial antibodies were detectable only in celiac sprue. Antigen adsorption resulted in a significant reduction of the anti-tissue transglutaminase either in celiac sprue or inflammatory bowel disease sera. A significant correlation between anti-tissue transglutaminase and Crohn’s disease activity index or integrated disease activity index scores was found. Anti-tissue transglutaminase was also detectable in fecal supernatants from inflammatory bowel disease patients. Data highlight that both circulating and intestinal anti-tissue transglutaminases are detectable in inflammatory bowel disease, and that they are related to disease activity. These features underline that, in addition to anti-tissue transglutaminase, an anti-endomysial antibody test is necessary in the diagnostic work-up of celiac sprue, especially in patients with known inflammatory bowel disease.

New developments in celiac disease

Celiac disease remains a challenge to the clinician and scientist. It is clearly more prevalent than was previously suspected. Much interest is seen in identifying the genetic factors, which predispose to disease and the environmental agents that can trigger it. Genome-wide searches have identified a number of chromosomal susceptibility loci. Specific gliadin epitopes are being analyzed. New diagnostic options include the tissue transglutaminase enzyme-linked immunosorbent assay. Neurologic disease and bone disease are intriguing complications of celiac disease and are gradually being defined.