Anti-gliadin antibodies in patients with celiac disease cross-react with enterocytes and human calreticulin

The impact of celiac disease and duration of gluten free diet on anterior and posterior ocular structures: Ocular imaging based study

PURPOSE

To evaluate the eyes of adult celiac disease (CD) patients and investigate the association between these ocular parameters with celiac specific antibodies and duration of gluten free diet (GFD).

METHODS

This cross-sectional study included 72 eyes of 36 CD patients (18-51 years of age) and 70 eyes of 35 age- and sex-matched healthy controls. In addition to a complete ophthalmologic examination, all patients were scanned by a Scheimpflug camera, specular microscopy and spectral domain optical coherence tomography.

RESULTS

Endothelial cell density (ECD), anterior chamber angle (ACA) degrees, anterior chamber depth (ACD), anterior chamber volume (ACV) and central macular thickness (CMT) values were lower in CD patients as compared with control group (p values = 0.038, 0.024, 0.002, 0.038 and 0.046 respectively). ECD and CMT were lower in celiac patients whom endomysial antibodies (EMA) IgA were positive (p = 0.001, p = 0.042 respectively). Tissue transglutaminase IgA antibody (anti tTG IgA) was weakly positively correlated (p > 0.05) with ACD, and positively (r = 0.319; p < 0.05) correlated with ACV. As the duration of compliance to the diet increased in the celiac group the mean and inferior retinal nerve fiber layer (RNFL) thickness decreased (p = 0.035, p = 0.008 respectively). Mean, inferior and temporal RNFL thicknesses were lower in celiac patients whose duration of GFD was longer than 5 years (p < 0.05).

CONCLUSIONS

Decreases in ECD, ACA degree, ACD, ACV and CMT can occur in CD patients. In adult celiac patients; ECD, CMT might be effected in the presence of positive EMA, and ACD, ACV might be effected in the presence of higher anti tTG IgA titer. Adult celiac patients who had longer duration of GFD may have thinner RNFL. RNFL may be thinner in celiac patients who comply with GFD for more than 5 years.

Anti-calreticulin antibodies and calreticulin in sera of patients diagnosed with dilated or hypertrophic cardiomyopathy

Distinct cellular level of the Ca²⁺-binding chaperone calreticulin (CRT) is essential for correct embryonal cardiac development and postnatal function. However, CRT is also a potential autoantigen eliciting formation of antibodies (Ab), whose role is not yet clarified. Immunization with CRT leads to cardiac injury, while overexpression of CRT in cardiomyocytes induces dilated cardiomyopathy (DCM) in animals. Hence, we analysed levels of anti-CRT Ab and calreticulin in the sera of patients with idiopatic DCM and hypertrophic cardiomyopathy (HCM). ELISA and immunoblot using human recombinant CRT and Pepscan with synthetic, overlapping decapeptides of CRT were used to detect anti-CRT Ab. Serum CRT concentration was tested by ELISA. Significantly increased levels of anti-CRT Ab of isotypes IgA (p < 0.001) and IgG (p < 0.05) were found in patients with both DCM (12/34 seropositive for IgA, 7/34 for IgG) and HCM (13/38 seropositive for IgA, 11/38 for IgG) against healthy controls (2/79 for IgA, 1/79 for IgG). Titration analysis in seropositive DCM and HCM patients documented anti-CRT Ab detected at 1/1600 dilution for IgG and 1/800 for IgA (and IgA1) and at least at 1/200 dilution for IgA2, IgG1, IgG2 and IgG3. Pepscan identified immunogenic CRT epitopes recognized by IgA and IgG Ab of these patients. Significantly increased levels of CRT relative to healthy controls were found in sera of patients with HCM (p < 0.01, 5/19). These data extend the knowledge of seroprevalence of anti-CRT Ab and CRT, and suggest possible involvement of autoimmune mechanisms directed to CRT in some forms of cardiomyopathies, which are clinically heterogeneous.

Protein kinase C delta is a substrate of tissue transglutaminase and a novel autoantigen in coeliac disease

Post-translational modification of proteins by deamidation or transamidation by tissue transglutaminase (tTG) has been suggested as a possible mechanism for the development of autoimmunity. Sequence analysis of protein kinase C delta (PKCδ) identified an amino acid motif that suggested the possibility that PKCδ was a glutamine substrate of tTG and MALDI-TOF analysis of synthesised peptides from PKCδ proved that this was the case. Polymerisation experiments using recombinant tTG and biotinylated hexapeptide substrate incorporation assays demonstrated that PKCδ is a substrate for tTG-mediated transamidation. Elevated levels of anti-PKCδ antibodies were detected in sera from patients with coeliac disease (p<0.0001) but not from patients with other autoimmune disorders. These data suggest that a subset of patients with coeliac disease produce autoantibodies against PKCδ and that this response may stem from a tTG-PKCδ substrate interaction.

[Serological diagnosis of celiac disease]

Screening studies using high-sensitivity and specificity markers indicate a prevalence of celiac disease of up to 1% in European and North-American populations. Celiac disease is a frequent condition that has become an important public health issue. Yet the majority of cases remain undiagnosed due to the polymorphism of its clinical manifestations. The new insight in the pathogenesis of celiac disease has lead to the development of new diagnostic tools. Early screening of symptomatic patients and pre-identified at-risk groups significantly improves the quality of life while reducing morbidity and mortality. However, prophylactic benefits of early diagnosis by assessing the general population have not been shown in any study. French and Northern American scientific societies have introduced serological testing in their newly revised strategies to diagnose celiac disease. Older markers judged insufficiently accurate like anti-gliadin and anti-reticulin antibodies have recently been withdrawn from the list of reimbursed medical expenses in France. Anti-endomysium and tissue transglutaminase IgA antibodies have proven to be at this day the most sensitive and specific markers for the diagnosis and follow-up of patients on gluten-free diet, at the exception of IgA-deficient patients. Assays testing for IgG antibodies are recommended upon IgA-deficiency. Although very accurate, a better standardisation of current assays may enable serological testing to replace in a near future histological confirmation brought by small bowel biopsies which remains today the gold standard test to diagnose celiac disease. Indeed, serological testing represents and attractive alternative as it is less invasive, less expansive, laboursaving and more objective in interpretation.

Identification of new autoantibody specificities directed at proteins involved in the transforming growth factor β pathway in patients with systemic sclerosis

Introduction

Antinuclear antibodies (ANAs), usually detected by indirect immunofluorescence on HEp-2 cells, are identified in 90% of patients with systemic sclerosis (SSc). Thus, approximately 10% of SSc patients have no routinely detectable autoantibodies, and for 20% to 40% of those with detectable ANAs, the ANAs do not have identified specificity (unidentified ANAs). In this work, we aimed to identify new target autoantigens in SSc patients.

Methods

Using a proteomic approach combining two-dimensional electrophoresis and immunoblotting with HEp-2 cell total and enriched nuclear protein extracts as sources of autoantigens, we systematically analysed autoantibodies in SSc patients. Sera from 45 SSc patients were tested in 15 pools from groups of three patients with the same phenotype. A sera pool from 12 healthy individuals was used as a control. Proteins of interest were identified by mass spectrometry and analysed using Pathway Studio software.

Results

We identified 974 and 832 protein spots in HEp-2 cell total and enriched nuclear protein extracts, respectively. Interestingly, α-enolase was recognised by immunoglobulin G (IgG) from all pools of patients in both extracts. Fourteen and four proteins were recognised by IgG from at least 75% of the 15 pools in total and enriched nuclear protein extracts, respectively, whereas 15 protein spots were specifically recognised by IgG from at least four of the ten pools from patients with unidentified ANAs. The IgG intensity for a number of antigens was higher in sera from patients than in sera from healthy controls. These antigens included triosephosphate isomerase, superoxide dismutase mitochondrial precursor, heterogeneous nuclear ribonucleoprotein L and lamin A/C. In addition, peroxiredoxin 2, cofilin 1 and calreticulin were specifically recognised by sera from phenotypic subsets of patients with unidentified ANAs. Interestingly, several identified target antigens were involved in the transforming growth factor β pathway.

Conclusions

We identified several new target antigens shared among patients with SSc or specific to a given phenotype. The specification of new autoantibodies could help in understanding the pathophysiology of SSc. Moreover, these autoantibodies could represent new diagnostic and/or prognostic markers for SSc.

Similarity of fine specificity of IgA anti-gliadin antibodies between patients with celiac disease and humanized α1KI mice

Gliadins, and primarily α-gliadins containing several sequences such as aa 31-49, aa 56-88 (33-mer), aa 57-68, and aa 69-82, are critical in the induction of immune response or toxic reaction leading to the development of celiac disease (CLD). The role of IgA anti-gliadin antibodies (IgA AGA) is unknown. To this end, we prepared several humanized monoclonal IgA AGA using transgenic α1KI mice. Employing Pepscan with overlapping decapeptides of α-gliadin we observed a robust similarity between the specificity of humanized mouse monoclonal IgA AGA and IgA AGA from patients with florid CLD. The common immunodominant region included several sequential epitopes localized in the N-terminal part of α-gliadin (QFQGQQQPFPPQQPYPQPQPFP, aa 29-50, and QPFPSQQPYLQL, aa 47-58). Notably, IgA AGA produced by clones 8D12, 15B9, 9D12, and 18E2 had significant reactivity against sequences localized in the 33-mer, LQLQPFPQPQ (aa 56-65) and PQLPYPQPQPFL (aa 69-80). Humanized mouse monoclonal IgA AGA that have a known specificity are suitable as standard in ELISAs to detect serum IgA AGA of CLD patients and for studying the AGA pathogenic role in CLD, especially for analyzing the translocation of complex of specific IgA antibodies and individual gliadin peptides through enterocyte barrier.

Absence of high‐affinity calreticulin autoantibodies in patients with systemic rheumatic diseases and coeliac disease

Calreticulin has been reported to be an autoantigen in various autoimmune connective tissue diseases and in coeliac disease. Previous studies have used incubation buffers with low salt and low detergent concentrations (low stringency conditions) with serum albumin or other proteins as a blocking agent. Using these conditions we found a relatively high level of non-specific binding in many sera. Antibodies to proteins that are used as blocking reagents in ELISA (bovine serum albumin (BSA), ovalbumin, skimmed milk powder) are frequently present in sera, and these may cause false-positive results. Moreover, the low isoelectric point of calreticulin and its chaperone properties may give rise to false-positive results under low stringency conditions. We report that the use of a simple buffer without protein (50 mM Tris, pH 7.5, 1% Tween 20, 0.3 M NaCl) removes most of the problems with unwanted binding (high stringency conditions). Using the high stringency conditions, we screened sera from 107 patients with systemic lupus erythematosus, sera from patients with other systemic autoimmune diseases and from children with coeliac disease for the presence of high-affinity calreticulin autoantibodies by immunoblotting and ELISA. None of the sera contained high-affinity calreticulin antibodies. It is concluded that calreticulin is not a common autoantigen in patients with autoimmune connective tissue diseases or coeliac disease.

Calreticulin, a multi-process calcium-buffering chaperone of the endoplasmic reticulum

Calreticulin is an ER (endoplasmic reticulum) luminal Ca2+-buffering chaperone. The protein is involved in regulation of intracellular Ca2+ homoeostasis and ER Ca2+ capacity. The protein impacts on store-operated Ca2+ influx and influences Ca2+-dependent transcriptional pathways during embryonic development. Calreticulin is also involved in the folding of newly synthesized proteins and glycoproteins and, together with calnexin (an integral ER membrane chaperone similar to calreticulin) and ERp57 [ER protein of 57 kDa; a PDI (protein disulfide-isomerase)-like ER-resident protein], constitutes the ‘calreticulin/calnexin cycle’ that is responsible for folding and quality control of newly synthesized glycoproteins. In recent years, calreticulin has been implicated to play a role in many biological systems, including functions inside and outside the ER, indicating that the protein is a multi-process molecule. Regulation of Ca2+ homoeostasis and ER Ca2+ buffering by calreticulin might be the key to explain its multi-process property.

Trypanosoma cruzi calreticulin: a possible role in Chagas' disease autoimmunity

Trypanosoma cruzi (T. cruzi) is the causative agent of Chagas' disease, an endemic and chronic illness that affects 18 million people in Latin America. The mechanisms underlying its pathogenesis are controversial. There is a growing body of evidence supporting the view that T. cruzi infection elicits severe autoimmune responses in the host, which significantly contribute to the pathogenesis of Chagas' disease, and several recent studies have reported the presence of autoantibodies and effector T lymphocytes against parasite and self antigens in infected patients and experimentally infected animals. T. cruzi calreticulin (TcCRT) is a 45kDa protein, immunogenic in humans, rabbits and mice. It has a high degree of homology with human (HuCRT) and mouse calreticulin (MoCRT), which would explain why an immune response to TcCRT could contribute to autoimmune reactions in Chagas' disease. Anti-TcCRT antibodies generated in A/J mice immunized with recombinant TcCRT (rTcCRT) reacted with rHuCRT and bound to neonatal and adult isogenic cardiomyocytes cultured in vitro. Interestingly, histological alterations, such as edema formation and cell infiltrates, which include CD3(+) cells, were detected in heart sections from immunized animals. Therefore, in rTcCRT-immunized mice, an autoimmune reaction against host CRT, paralleled by histological cardiac alterations, suggests a role of the parasite molecule in the induction of immunologically mediated heart tissue damage. The data presented here propose that TcCRT participates in the induction of cardiac autoimmunity in Chagas' disease.

Autoantibodies in celiac disease

Autoantibody production is an important feature of many autoimmune disorders, signifying a breakdown of immune tolerance to self-antigens. In celiac disease, an autoimmune enteropathy with multiple extra-intestinal manifestations, autoantibody reactivity to transglutaminase 2 (TG2) has been shown to closely correlate with the acute phase of the disease. It serves as a specific and sensitive marker of celiac disease, and is highly useful in aiding diagnosis and follow-up. Immune reactivity to other autoantigens, including transglutaminase 3, actin, ganglioside, collagen, calreticulin and zonulin, among others, has also been reported in celiac disease. The clinical significance of these antibodies is not known, although some may be associated with specific clinical presentations or extra-intestinal manifestations of celiac disease. This review examines the presence of anti-TG2 and other autoantibodies in celiac disease, discussing their diagnostic value, their potential role in disease pathogenesis and current hypotheses that explain how their release may be triggered.

Immune cross-reactivity in celiac disease: anti-gliadin antibodies bind to neuronal synapsin I

Celiac disease is an immune-mediated disorder triggered by ingestion of wheat gliadin and related proteins in genetically susceptible individuals. In addition to the characteristic enteropathy, celiac disease is associated with various extraintestinal manifestations, including neurologic complications such as neuropathy, ataxia, seizures, and neurobehavioral changes. The cause of the neurologic manifestations is unknown, but autoimmunity resulting from molecular mimicry between gliadin and nervous system proteins has been proposed to play a role. In this study, we sought to investigate the immune reactivity of the anti-gliadin Ab response toward neural proteins. We characterized the binding of affinity-purified anti-gliadin Abs from immunized animals to brain proteins by one- and two-dimensional gel electrophoresis, immunoblotting, and peptide mass mapping. The major immunoreactive protein was identified as synapsin I. Anti-gliadin Abs from patients with celiac disease also bound to the protein. Such cross-reactivity may provide clues into the pathogenic mechanism of the neurologic deficits that are associated with gluten sensitivity.

Specificity analysis of anti-gliadin mouse monoclonal antibodies used for detection of gliadin in food for gluten-free diet

A gluten-free diet (GFD) is the sole effective long-lasting treatment of celiac disease. Four monoclonal antibodies (Abs) were prepared by immunization of animals kept on GFD with gliadin. The specificity of these Abs to decapeptides of alpha- and gamma-gliadin and omega-secalin was analyzed by the PEPSCAN technique. Repetitive sequences of alpha- and gamma-gliadin and omega-secalin containing the motifs QPFPXQ (X = Q, L, P) were recognized by all Abs tested. These Abs also frequently reacted with peptides containing the sequences QQSFPQQ, QQTFPQP, and QPFRPQ. On the basis of PEPSCAN results two Abs--8D4 and 7C6--were selected for the construction of a new ELISA kit for the detection of gliadin in food. The comparison of data obtained using the newly developed ELISA kit and commercially available ones indicated that Abs selection on the basis of their fine specificity to gliadin is useful for sensitive detection of gliadin in foods.

Associated autoantibodies in celiac disease

Celiac disease (CD) is a life-long inflammatory autoimmune condition of the gastrointestinal tract affecting genetically susceptible individuals. Several autoimmune disorders are more prevalent in patients and their close relatives and that risk is gluten exposure duration related. The most frequent reported CD associated conditions are type 1 diabetes mellitus and autoimmune thyroiditis. Associated autoimmune antibodies are frequent in CD and their first-degree relatives, spanning anti-endocrine, anti-gastrointestinal, anti-nuclear, anti-cytoskeleton and anti-neurological antibodies. More specifically, antibodies against thyroid and the endocrine pancreas, anti-gastric and liver, anti-nuclear constituents, anti-reticulin, actin, smooth muscle, calreticulin, desmin, collagens and bone, anti-brain, ganglioside, neuronal and blood vessel were described in sera of the patients in numerous studies. The common immunogenetic theories for the above associations are: sharing common HLA and non-HLA genes, antigenic mimicry, damage-induced neoantigen exposure, altered intestinal permeability, idiotype network dysregulation and epitope spreading. The CD associated autoantibodies enigma, being an epiphenomenon or pathogenic, remains unresolved and presents a challenging area for future research.

Antibodies contained in “M” component of some patients with multiple myeloma are directed to food antigens?

Multiple myeloma is malignant disease that is characterized in most patients, by the presence in the serum of monoclonal gamma globulins, which in agarose gel after electrophoresis appear as protein band of restricted mobility, "M" component. The aim of this study was to determine are the antibodies contained in M-component directed to some antigen chronically present in the organism, to some of food antigens. Seventeen patients with secretory plasmacytoma were included in the study: eight of them had IgG(kappa), three had IgG(lambda), and one had biclonal IgG(kappa) and IgA(kappa), while two had IgA(kappa), the other two IgA(lambda) and one IgM(lambda) as paraproteins. M-proteins were detected analyzing patients' sera by agarose gel electrophoresis in 0.09 M barbital buffer. The each M-protein was confirmed by immunotyping (immunofixation) with corresponding antihuman antibodies directed to heavy or light chains of immunoglobulins. After the patients serum separation on agarose gel by electrophoresis, fresh 0.4% solution of crude gliadin (Sigma) in 1% SDS was put over the slides for immunoprecipitation. Preliminary results showed the interaction of gliadin with patient's serum proteins present in the protein fraction of the same mobility as it was the mobility of the M-component, in 6 from 17 investigated sera. These results are the first reporting that in sera of some patients with multiple myeloma antibodies from M-component could be directed to some of gliadin antigens. As the serum antigliadin immunoreactivity is present in patients with gluten intolerance, celiac disease, it could be of importance to elucidate is the multiple myeloma more severe form of gluten intolerance than celiac disease.

Impaired Cytolytic Activity in Calreticulin-Deficient CTLs

Calreticulin is an endoplasmic reticulum-resident chaperone that is stored in the cytotoxic granules of CTLs and NK cells and is released with granzymes and perforin upon recognition of target cells. To investigate the role of calreticulin in CTL-mediated killing, we generated CTL lines from crt(+/+) and crt(-/-) mice expressing a constitutively active form of calcineurin in the heart. Crt(-/-) CTLs showed reduced cytotoxic activity toward allogeneic target cells despite normal production, intracellular localization, and activity of granzymes and despite perforin overexpression. Comparable or higher amounts of granzymes were degranulated by crt(-/-) cells in response to immobilized anti-CD3 Abs, indicating that calreticulin is dispensable for the signal transduction that leads to granule exocytosis. The ability to form conjugates with target cells was affected in the crt(-/-) CTLs, explaining the observed reduction in cytotoxicity. Conjugate formation and cytotoxicity were completely restored by treatments that facilitate recognition and contact with target cells, a prerequisite for degranulation and killing. Therefore, we conclude that calreticulin is dispensable for the cytolytic activity of granzymes and perforin, but it is required for efficient CTL-target cell interaction and for the formation of the death synapse.

Role of calreticulin from parasites in its interaction with vertebrate hosts

Although parasites range from protozoan to complex, evolutionary advanced arthropods, in general, a hallmark of parasite life cycles is their ability to adapt to changes in temperature, pH and host defense strategies. Calreticulin, a calcium-binding protein, highly conserved and multifunctional, is present in every cell of higher organisms, except erythrocytes. The surprising array of calreticulin-associated functions include lectin-like chaperoning, calcium storage and signaling, modulation of gene expression, cell adhesion, enhancement of phagocytosis of C1q or collectin opsonized apoptotic cells, inhibition of angiogenesis and tumoral growth, inhibition of perforin pore formation in T and NK cells, and inhibition of C1q-dependent complement activation. Likewise, calreticulin is present in a wide spectrum of sub cellular compartments. Parasite calreticulin shows a surprisingly high degree of conservation within the framework of its functional domains. Its role within the parasite/host relationship needs to be assessed further, in particular with regard to its impact on parasite infectivity, by helping to evade from its hosts' immune response. With special emphasis on calreticulin from Trypanosoma cruzi, the intracellular protozoan agent of American trypanosomiasis (Chagas' disease), we wish to exemplify and highlight the various implications of parasite calreticulin, within the pathophysiology of parasite-mediated human and animal disease.

Gliadin, endomysial and thyroid antibodies in patients with latent autoimmune diabetes of adults (LADA)

Latent autoimmune diabetes of adults (LADA) manifested after the age of 35 is characterized by the presence of disease-specific autoantibodies (anti-glutamate decarboxylase GADAb, anti-IA2Ab). However, autoimmunity in Type 1 diabetes mellitus is not targeted only to pancreatic beta-cells. No data have so far been published concerning the antibodies associated with other autoimmune disease in LADA patients. The presence of anti-thyroglobulin (TGAb), anti-thyroid peroxidase (TPOAb), anti-gliadin IgA (AGAAb) and IgG (AGGAb) and endomysial antibodies (EMAb) in sera of 68 diabetics typed as LADA was compared with the antibody presence in sera of 85 patients with Type 2 diabetes. We found a significantly higher occurrence of gliadin antibodies in LADA patients: the rate of AGGAb was 19.1% in comparison with 3.5% in the T2DM group (P = 0.0026), the rate of AGAAb was 13.2% in comparison with 3.5% (P = 0.035). The prevalence of EMAb was very low in both groups (1.5% and 0). The two groups differed significantly in the TPOAb rate: 22.1% in LADA compared to 9.4% in T2DM (P = 0.04), whereas no significant difference was found in the presence of TGAb (8.8% and 3.5%, P = 0.187). In comparison with T2DM patients, LADA patients were found to express higher antibody activity against gluten-related antigens and against TPO.

Tissue transglutaminase-serology markers for coeliac disease

Serology markers of coeliac disease (CD) - antigliadin IgA/IgG antibodies (AGA/AGG) with purified alpha-gliadin, antiendomysium IgA antibodies (EmA) and anti-tissue transglutaminase (atTG) IgA/IgG antibodies--determined in 1451 serum samples, were analysed with respect to different screening algorithms. Determination of atTG using five ELISA methods was compared taking into account the impact of human recombinant antigen and IgG class of atTG. A subgroup of 119 patients undergoing small intestinal biopsy was used to calculate sensitivity and specificity of CD markers. The highest sensitivity (94%) was obtained for AGG, and the highest specificity (93.5%) was obtained for EmA. All coeliac disease patients were detected using the combination of all four CD markers, resulting in 100% sensitivity. CD and type 1 diabetes mellitus autoantigens were determined in 139 diabetic patients. The atTG IgA mean value (16.7 IU/ml) was higher in the antiglutamate dehydrogenase antibody (GAD)-positive subgroup, where at least one CD marker was positive in 83.6% subjects. In the GAD-negative subgroup atTG IgA was 8.73 lU/ml and at least one CD marker was positive in 57.4% subjects. atTG in IgA and IgG classes could be recommended as valuable serological markers of CD in the differential diagnosis of malabsorption as well as in various screening algorithms. ELISA determination of atTG with human antigen could increase the specificity, especially in patients with other autoimmune diseases.

The serologic screening for celiac disease in the general population (blood donors) and in some high-risk groups of adults (patients with autoimmune diseases, osteoporosis and infertility) in the Czech republic

The prevalence of celiac disease (CD) was determined in healthy blood donors and in high-risk groups of adults (a total of 1835 adults--randomly selected 1312 healthy blood donors, 102 patients with primary osteoporosis, 58 patients with autoimmune diseases and 365 infertile women). It was calculated on the basis of a two-step serologic screening method--in the first step IgA and IgG antigliadin antibodies (AGA) and IgA anti-gamma-glutamyltransferase ('transglutaminase') antibodies (ATG) were estimated, in the second step sera positive for IgA AGA and/or IgA ATG were examined for antiendomysial IgA (AEA) antibodies. Immunoenzymic assay (ELISA) was used for determining of AGA and ATG antibodies; immunofluorescence method, performed on human umbilical cord tissue, was used for assaying of AEA antibodies. Total serum IgA level in only IgG AGA positive subjects was measured by routine turbidimetric method. 0.45% of healthy blood donors, 0.98% of osteoporotic patients, 2.7% of patients suffering from autoimmune disease and 1.13% of women with infertility considered as immunologically mediated were found to be positive in both steps of serologic screening (AGA and/or ATG and antiendomysium positive). The presumed high prevalence of seropositivity for CD in apparently healthy Czech adult population was confirmed. In the high-risk groups, the prevalence of seropositivity for CD was approximately 2-4 times higher than in healthy blood donors. The real prevalence of CD in the tested groups, however, can be estimated after performing small intestinal biopsy in the seropositive patients.

Increased levels of IgA antibodies against desmin in children with coeliac disease

BACKGROUND

In addition to IgA anti-endomysial antibodies, IgA anti-smooth muscle antibodies have been observed in a number of patients with coeliac disease (CoD), but only limited data exist on the frequency and antigen specificity of IgA against cytoskeletal proteins in CoD.

METHODS

We evaluated the sera of 42 untreated CoD patients, follow-up sera of 26 CoD patients after treatment, and 116 control sera for IgA reactivity to cytoskeletal proteins from the human umbilical cord (HUC) by immunoblotting, and compared the results with anti-tissue transglutaminase IgA (anti-tTG IgA) ELISA and immunofluorescence results.

RESULTS

Serum IgA from CoD patients most frequently recognized a 57-kD antigen in HUC cytoskeletal extract, identified as desmin using mass spectrometry and internal peptide sequencing. Increased IgA reactivity to the human desmin band was detected in 22 children with untreated CoD (52.4%), in 4 treated CoD patients (15.4%), and in 12 control subjects (10.3%) (p < 0.01); similar results were obtained with anti-chicken desmin IgA ELISA. Anti-tTG IgA levels (increased in 71.4% of untreated CoD patients) correlated significantly with anti-desmin IgA levels in untreated CoD, and both autoantibody reactivities decreased in response to a gluten-free diet. Pre-adsorption experiments and affinity purification of anti-desmin IgA antibodies further confirmed that desmin is an IgA autoantigen in CoD and is recognized by antibodies which are not cross-reactive with tTG.

CONCLUSIONS

Anti-desmin IgA antibodies are frequently occurring if not the predominant cytoskeletal antibodies in children with untreated CoD and could be related to the disease process in the small intestine.

Serologic markers of untreated celiac disease in Libyan children: antigliadin, antitransglutaminase, antiendomysial, and anticalreticulin antibodies

BACKGROUND

There are, as yet, no data available about the incidence of celiac disease in Libya. The aim of this study was to test the occurrence of serologic markers in a group of Libyan children with positive clinical and histologic findings indicative of celiac disease diagnosis.

METHODS

Thirty-nine children with untreated celiac disease and 50 healthy school children, all younger than 14 years, were included in the study. Enzyme-linked immunosorbent assay for immunoglobulin G and immunoglobulin A (IgA) antigliadin, antitissue transglutaminase, and anticalreticulin antibodies was used to evaluate the serologic markers of the celiac patients. Immunoglobulin A antiendomysial antibodies were detected by indirect immunofluorescence using human umbilical cord tissue.

RESULTS

Clinical symptoms at presentation were weight loss (82%), abdominal distension (61.5%), diarrhea or steatorrhea (59%), pallor (41%), abdominal pain (20.5%), constipation (15%), vomiting (10%), and short stature (7.7%). Most of these symptoms disappeared after introduction of a gluten-free diet. Of 39 patients, only 23 (59%) were endomysium positive and positive also in all other serologic markers. The second group of patients with positive clinical and biopsy findings but antiendomysial antibody-negative findings was subdivided into two subgroups according to the IgA antigliadin antibody results. Individuals in the IgA gliadin-negative subgroup also lacked IgA autoantibodies.

CONCLUSIONS

The authors' findings stress the importance of serologic testing not only for screening but also for confirmation of celiac disease.

IgG subclass profile of serum antigliadin antibodies and antibody-dependent cell-mediated cytotoxicity in young children with coeliac disease

Recently, sera from children with active coeliac disease were found to efficiently induce antibody-dependent cell-mediated cytotoxicity (ADCC) of gliadin-coated cells. In the present study, the subclass profile of immunoglobulin (Ig)G antigliadin antibodies in sera from young children, with or without coeliac disease, was determined and related to the ADCC-mediating capacity of the same sera. In addition, IgG subclasses were selectively depleted from sera and the effect on ADCC-mediating was studied. Children with untreated coeliac disease had high antigliadin antibody activities of all four IgG subclasses. However, they had a particularly high proportion of IgG1 antigliadin antibodies (ratio IgG1/IgG) compared with healthy references or coeliac children in remission. In contrast, children who had high serum antigliadin antibody activity but no histological signs of enteropathy (disease references), showed significantly lower proportions of antigliadin antibodies of the IgG1 as well as the IgG3 subclass compared with healthy references or untreated coeliac children. Regression analysis showed that IgG1 and IgG3 antigliadin antibody activity correlated positively to ADCC-mediating capacity, and depletion of IgG1 from sera profoundly diminished ADCC. The results suggest that gliadin-specific antibodies of predominantly the IgG1 subclass mediate tissue-damaging immune reactions like ADCC, and may, thus, contribute to the disease process of coeliac disease.

Occurrence of IgA and IgG autoantibodies to calreticulin in coeliac disease and various autoimmune diseases

Calreticulin (CRT), a high-affintiy calcium binding protein and chaperone, was recently identified as one of the targets of autoantibodies in coeliac disease. We evaluated the level of IgA and IgG antibodies to CRT in sera from patients with coeliac disease and various autoimmune diseases. The level of antibodies to gliadin (shown previously to cross-react with CTR), isolated enterocytes and tissue transglutaminase were determined for comparison. The mean level of IgA antibodies to CRT was significantly higher (P< 0.001) in sera from coeliac patients with active disease (139.9+/-11.2 AU/+/-SE) than in healthy controls (20.9+/-1.7 AU). In sera of patients with systemic lupus erythematosus (SLE), insulin dependent diabetes mellitus (IDDM), multiple sclerosis (MS) and autoimmune thyroiditis (AT) or inflammatory bowel disease (IBD) the mean level (25.8+/-3.7 to 38.1+/-5.6 AU) did not exceed the cut-off value. A low level of these antibodies, however, was detected in some sera of patients with MS and IBD. The level of IgG anti-CRT antibodies was increased in coeliac patients (mean 125.4+/-8.0 AU, P< 0.001) when compared to that in healthy controls (33.9+/-2.3 AU). The IgG anti-CRT antibodies were also detected in about 30% of SLE patients sera (54.1+/-3.6 AU, P< 0.001), but the mean level reached only half that detected in coeliac patients.

Role of immunosuppressive therapy in refractory sprue-like disease

Patients with malabsorption and histological findings consistent with celiac disease, who are unresponsive to gluten free diet, and in whom other causes of flat mucosa have been excluded, are considered to suffer from so called unclassified or refractory sprue. Although the true nature of this condition needs to be further elucidated, it is known to represent a difficult therapeutical problem with potentially fatal course. Herein, we report a patient with refractory sprue-like disease who after failing to respond to corticosteroids and TPN was in a critical condition. He responded promptly to cyclosporine and made a remarkable recovery. In contrast to previous reports, the cyclosporine treatment in this patient was pursued only for 1 month, whereupon the patient turned responsive to steroids. Subsequent treatment with azathioprine allowed corticosteroids to be reduced to a low maintenance dose and eventually all drugs could be discontinued without reappearance of symptoms. Cyclosporine therapy might be lifesaving in occasional patients with refractory sprue-like disease and it may result in reversal of steroid resistance. Moreover, azathioprine seems to have a steroid sparing effect in this setting. Short term immunosuppressive treatment may have an advantage of lower risk for drug related side effects.

Malabsorption syndromes

BACKGROUND/AIMS

Malabsorption syndromes commonly result from a pathological interference of the normal digestive process. There have been major advances in the last 4 years. The purpose of this review is to highlight in the form of a brief summary the most outstanding information available.

METHODS

The review was performed based on a medical literature search using MEDLINE (1993-1997), bibliographic reviews of book chapters and review articles. As a consequence of the extensive information incorporated in the period and the limited scope of this review, the review will focus in three aspects: (1) an overview on some clinical aspects of malabsorption; (2) diseases in which predominates the disturbed mucosal phase of the digestive process, and (3) providing information on diagnostic testing regarding malabsorption.

RESULTS

Major advances on celiac disease, Whipple's disease, giardiasis, tropical sprue, malabsorption of oligo- and disaccharides, vitamin B12 and bile salts are discussed. New aspects on diagnostic procedures for malabsorption are also presented.

CONCLUSION

Although major advances have given a great support to the investigation of malabsorption, yet the syndrome remains a major diagnostic dilemma. Based on the limited availability of most diagnostic tests, a simple and practical diagnostic algorithm is presented.