A gene-centric approach to biomarker discovery identifies transglutaminase 1 as an epidermal autoantigen.

Autoantigen discovery is a critical challenge for the understanding and diagnosis of autoimmune diseases. While autoantibody markers in current clinical use have been identified through studies focused on individual disorders, we postulated that a reverse approach starting with a putative autoantigen to explore multiple disorders might hold promise. We here targeted the epidermal protein transglutaminase 1 (TGM1) as a member of a protein family prone to autoimmune attack. By screening sera from patients with various acquired skin disorders, we identified seropositive subjects with the blistering mucocutaneous disease paraneoplastic pemphigus. Validation in further subjects confirmed TGM1 autoantibodies as a 55% sensitive and 100% specific marker for paraneoplastic pemphigus. This gene-centric approach leverages the wealth of data available for human genes and may prove generally applicable for biomarker discovery in autoimmune diseases.

Simultaneous detection of IgA and IgG antibodies against tissue transglutaminase: The preferred pre-biopsy test in childhood celiac disease.

OBJECTIVES: IgA antibodies against tissue transglutaminase (anti-TG2) is a reliable marker of celiac disease (CD). However, IgA-deficient patients are not identified and young children may lack IgA anti-TG2. Combined detection of IgA and IgG (IgA/IgG) against deamidated gliadin peptides (DGP) has shown a high diagnostic performance for untreated CD. Here we examined the utility of IgA/IgG anti-TG2, IgA/IgG anti-DGP and IgA/IgG against a mix of TG2 and DGP (anti-TG2/DGP) in finding CD among children. METHODS: Serum antibodies against TG2, DGP, and TG2/DGP were determined with ELISA in 242 children referred to a paediatric gastroenterologist. Fifty had untreated CD verified by an intestinal biopsy and 192/242 children had other diseases than CD. RESULTS: Forty-eight untreated CD children had increased IgA/IgG anti-TG2, 47/50 had increased IgA/IgG anti-DGP and 46/50 had increased IgA/IgG anti-TG2/DGP. One control subject had increased IgA/IgG anti-TG2 and IgA/IgG anti-TG2/DGP, whereas 7/192 control subjects had increased IgA/IgG anti-DGP. The IgA/IgG anti-TG2 assay had the best performance with a sensitivity of 96%, a specificity of 99.5% and the area under the ROC-curve was 0.996 (95% CI 0.992-1, p < 0.0001). CONCLUSIONS: Detection of one antibody is not sufficient when screening for untreated CD among children due to cases of IgA deficiency. The inclusion of DGP antigens in the IgA/IgG combination assays seems to affect the sensitivity and specificity negatively, whereas detection of IgA/IgG anti-TG2 has the potential of finding most untreated CD patients, including those with IgA deficiency.

Silent coeliac disease is over-represented in children with type 1 diabetes and their siblings.

AIM: This study measured autoantibodies against tissue transglutaminase (anti-tTG) to detect untreated coeliac disease in children with type 1 diabetes and their siblings. METHODS: Anti-tTG was measured in prospectively collected sera from 169 children at the onset of diabetes, 88 of their siblings and 96 matched control children. Coeliac disease was confirmed with a small intestinal biopsy. RESULTS: Coeliac disease was diagnosed in five children before diabetes onset. A further 12 children were diagnosed after diabetes onset, without any gastrointestinal symptoms, and 11 of these had anti-tTG at the onset of diabetes, with the remaining child showing seroconversion within 6 months. Hence, all the children with both diseases had anti-tTG at or before diabetes diagnosis, and the prevalence of coeliac disease was 10.1%. Moreover, 6.8% of the siblings and 3.1% of the control children had elevated levels of anti-tTG. None of the siblings reported any coeliac-related symptoms, despite being positive for anti-tTG, and coeliac disease has so far been biopsy confirmed in 4.5%. CONCLUSION: Silent coeliac disease is over-represented in children with type 1 diabetes and their siblings. All diabetes children and their siblings should be tested and followed for the presence of anti-tTG and coeliac disease.

A single conformational transglutaminase 2 epitope contributed by three domains is critical for celiac antibody binding and effects.

The multifunctional, protein cross-linking transglutaminase 2 (TG2) is the main autoantigen in celiac disease, an autoimmune disorder with defined etiology. Glutamine-rich gliadin peptides from ingested cereals, after their deamidation by TG2, induce T-lymphocyte activation accompanied by autoantibody production against TG2 in 1-2% of the population. The pathogenic role and exact binding properties of these antibodies to TG2 are still unclear. Here we show that antibodies from different celiac patients target the same conformational TG2 epitope formed by spatially close amino acids of adjacent domains. Glu153 and 154 on the first alpha-helix of the core domain and Arg19 on first alpha-helix of the N-terminal domain determine the celiac epitope that is accessible both in the closed and open conformation of TG2 and dependent on the relative position of these helices. Met659 on the C-terminal domain also can cooperate in antibody binding. This composite epitope is disease-specific, recognized by antibodies derived from celiac tissues and associated with biological effects when passively transferred from celiac mothers into their newborns. These findings suggest that celiac antibodies are produced in a surface-specific way for which certain homology of the central glutamic acid residues of the TG2 epitope with deamidated gliadin peptides could be a structural basis. Monoclonal mouse antibodies with partially overlapping epitope specificity released celiac antibodies from patient tissues and antagonized their harmful effects in cell culture experiments. Such antibodies or similar specific competitors will be useful in further functional studies and in exploring whether interference with celiac antibody actions leads to therapeutic benefits.

No difference in markers of adipose tissue inflammation between overweight women with polycystic ovary syndrome and weight-matched controls.

UNLABELLED: BACKGROUND; Previous studies have indicated that peripheral circulating markers of inflammation are elevated in women with polycystic ovary syndrome (PCOS), but thus far no studies concerning markers of inflammation in adipose tissue have been published. The aim of the study was to investigate whether patients with PCOS display increased expression of inflammatory markers in adipose tissue. METHODS: Twenty overweight patients with PCOS, 10 lean patients with PCOS and 20 overweight controls had subcutaneous fat biopsies and blood samples taken. Adipose tissue levels of mRNA of inflammatory markers were determined by use of real-time PCR. RESULTS: Overweight patients with PCOS had higher relative adipose tissue chemokine ligand 2 (P < 0.01), and its cognate receptor (P < 0.05), tumour necrosis factor-α (P < 0.001), interleukin (IL)-10 (P < 0.001) and IL-18 (P < 0.001) and the monocyte/macrophage markers CD14 (P < 0.01) and CD163 (P < 0.01) mRNA levels compared with lean women with PCOS. There were no differences between overweight patients with PCOS and overweight control subjects in this respect. Within the PCOS group, markers of adipose tissue inflammation correlated significantly with obesity-related metabolic disturbances, but when data were adjusted for age and BMI, most correlations were lost. CONCLUSIONS: Overweight, rather than the PCOS diagnosis per se, appears to be the main explanatory variable for elevated adipose tissue inflammation in patients with PCOS.

Patients with polycystic ovary syndrome have lower levels of IgM anti-phosphorylcholine antibodies than healthy women.

INTRODUCTION: IgM antibodies against phosphorylcholine (IgM anti-PC) are natural autoantibodies, possibly exerting one of the atheroprotective functions of the immune system. Increased levels of these antibodies reduce the development of atherosclerosis in mice, and low levels of IgM anti-PC have been associated with increased risk for cardiovascular disease (CVD). This study compared levels of IgM anti-PC in women with polycystic ovary syndrome (PCOS, n = 111) and healthy controls (n = 79). METHOD: Levels of IgM anti-PC were measured with ELISA. RESULTS: The median level of IgM anti-PC in patients with PCOS was not significantly different compared to control subjects. However, the proportion of patients with PCOS with low levels of IgM anti-PC, defined as number of individuals below the median level, was significantly higher than among healthy controls, p < 0.05. Patients with PCOS in the oldest age quintile had significantly lower level of IgM anti-PC than control subjects of similar age (p < 0.05) and younger women with PCOS (p < 0.01). CONCLUSION: Our results indicate that women with PCOS more frequently display below-median levels of IgM anti-PC than controls and older women with PCOS have lower median anti-PC levels. Further studies of how this finding translates into actual CVD risk in women with PCOS are needed.

Low levels of IgM antibodies to phosphorylcholine predict cardiovascular disease in 60-year old men: effects on uptake of oxidized LDL in macrophages as a potential mechanism.

OBJECTIVE: We here determine the role of IgM antibodies against phosphorylcholine (anti-PC) in prediction of cardiovascular disease (CVD) and on macrophage uptake of Oxidized LDL (OxLDL). METHODS: From a screening of 4232 subjects, 60-year-old (2039 men and 2193 women), 211 incident cases of CVD (myocardial infarction, ischemic stroke, or hospitalized angina pectoris) and 633 age- and sex-matched controls were identified through a 5-7 year follow-up. Serum levels of IgM anti-PC was determined by ELISA. Anti-PC was extracted from pooled human IgM and the effect of anti-PC on the uptake of OxLDL was studied by FACScan. RESULTS: Relative risks (RR) with 95% confidence intervals (CI) by quartiles of anti-PC levels with quartile 4 set as the reference value (RR = 1.0) and adjusted for smoking, BMI, type II diabetes, hypercholesterolaemia, and high blood pressure yielded an excess risk for CVD only for those within the lowest quartile of anti-PC values with an RR of 1.37 (CI 0.87-2.16). However, for men stronger associations were noted with increasing multivariately adjusted RRs from quartile 4 to quartile 1. Subjects within quartile 1 (values below 29.7 U/ml) had a significantly increased RR of 1.96 (CI 1.09-3.55). Further adjustments for hsCRP gave essentially the same results. No excess risk was noted for women. Specific anti-PC could be extracted from IgM and these antibodies inhibited macrophage uptake of OxLDL. CONCLUSIONS: Low IgM anti-PC could be a novel risk marker for CVD among men. One possible mechanism could be inhibition of uptake of oxLDL in macrophages.

Prediction of clinical and mucosal severity of coeliac disease and dermatitis herpetiformis by quantification of IgA/IgG serum antibodies to tissue transglutaminase.

OBJECTIVES: We analysed whether the quantification of autoantibodies against tissue transglutaminase could be used to predict mucosal destruction and disease severity in patients with gluten sensitivity. PATIENTS AND METHODS: One hundred seventy patients with coeliac disease (CD), comprising 52 children with severe malabsorption (group I), 59 children with mild symptoms (group II), 59 adults (group III), 134 patients with dermatitis herpetiformis (DH), and 131 disease controls, were studied. Serial serum samples of patients in groups I and II on a gluten-free diet were also included. Serum levels of antibodies against recombinant tissue transglutaminase were determined with ELISA using standard curves for quantification of antibodies. RESULTS: Immunoglobulin (Ig)A antibodies against tissue transglutaminase (IgA-TGA) were detected in all of the patients with CD and in 95% of the DH patients. The IgA-TGA and IgG-TGA levels were higher in group I (P < 0.001). The IgG-TGA levels and positivity rate in group I (100%) were higher than in group II (81%), group III (73%), and the DH group (67%). Elevated IgA-TGA and IgG-TGA levels in combination predicted a more severe small intestinal atrophy (P < 0.0001) with a specificity of 99% for Marsh IIIb-IIIc (flat) lesions. The kinetics of the IgA-TGA decrease during diet differed between groups I and II. CONCLUSIONS: High levels of IgA-TGA and IgG-TGA antibodies were associated with the grade of mucosal villous atrophy and a more severe clinical presentation. The combined measurement of IgA-TGA and IgG-TGA enables a noninvasive prediction of small intestinal villous atrophy with high accuracy, and may reduce the need for a biopsy in patients with suspected CD.

Protein A and protein G ELISA for the detection of IgG autoantibodies against tissue transglutaminase in childhood celiac disease.

OBJECTIVES: To investigate if the detection of celiac disease (CD) in children was improved by using alternative conjugates for assessment of tissue transglutaminase (tTG) autoantibodies. METHODS: Serum samples from 108 biopsy confirmed CD children and 42 control subjects were investigated for the presence of autoantibodies with tTG coated microplates using protein A (PA), protein G (PG), anti-IgG, or anti-IgA as conjugates. RESULTS: Of the 108 CD children, 86 (80%) were IgG-tTG positive, 91 (84%) were positive with the PA-conjugate, 94 (87%) were positive with the PG-conjugate, and 103 (95%) were IgA-tTG positive. Among the 42 controls, 4 (10%) were IgG-tTG positive, 5 (12%) were positive with both the PA- and PG conjugates, whereas 3 (7%) were IgA-tTG positive. Compared with IgG-tTG the concordance was 93% for PA and 95% for PG, with a positive correlation between antibody levels (r=0.967 and r=0.975, p<0.0001). All but one CD child were found positive by combining IgG-tTG and IgA-tTG detection. CONCLUSIONS: The sensitivity of IgG-tTG detection with ELISA increased by protein A or protein G conjugates, whereas the specificity was reduced as compared with anti-IgG conjugate. The combined measurement of IgA-tTG and IgG-tTG still seems to be the optimal procedure when screening children for CD.

Deamidated gliadin peptides form epitopes that transglutaminase antibodies recognize.

OBJECTIVE: Deamidated gliadin peptides are efficient antigens in diagnostic tests for celiac disease, and results correlate better with transglutaminase 2-based assays than those with native gliadin. We investigated whether deamidated gliadin antigens are structurally similar to transglutaminase 2 or could mimic transglutaminase epitopes. PATIENTS AND METHODS: Serum samples from 74 celiac and 65 control patients, and 13 different transglutaminase 2-specific monoclonal mouse antibodies were investigated for their binding to commercially available deamidated gliadin peptides using enzyme-linked immunosorbent assay, competition studies, and molecular modelling. RESULTS: The enzyme-linked immunosorbent assay with deamidated gliadin peptides had 100% sensitivity and 98.5% specificity in patients. Deamidated gliadin epitopes also were recognized by 3 transglutaminase-specific monoclonal antibodies, and antibodies affinity-purified with deamidated gliadin peptides from celiac patient sera reacted with transglutaminase but did not show endomysial binding. The binding of the monoclonal antibodies to deamidated gliadin was inhibited dose dependently by full-length recombinant human transglutaminase, its fragments containing the binding sites of these monoclonal antibodies, or by celiac patient antibodies. Deamidated gliadin peptides decreased the binding of transglutaminase-specific monoclonal antibodies to transglutaminase. Three different cross-reacting transglutaminase epitopes were found, of which 2 are located in the C-terminal domain and 1 is conformational. The binding of celiac serum samples to deamidated gliadin peptides could not be abolished by transglutaminase or by any of the transglutaminase-specific monoclonals, indicating that celiac sera also contain additional antibodies to gliadin epitopes different from transglutaminase. CONCLUSIONS: Certain deamidated gliadin-derived peptides and transglutaminase 2 epitopes have similar 3-dimensional appearance. This homology may contribute to the induction of transglutaminase autoantibodies by molecular mimicry.

Antigliadin immunoglobulin A best in finding celiac disease in children younger than 18 months of age.

OBJECTIVES: The aim was to investigate age-dependent serum levels and occurrence of elevated celiac disease (CD)-related antibodies in young children, to define the optimal serological procedure when selecting for small intestinal biopsy. PATIENTS AND METHODS: Included were 428 children with biopsy verified CD (median age 16 months; range 7.5 months-14 years) and 216 controls (median age 2.7 years; range 8.5 months-14.6 years). Immunoglobulin (Ig) A antibodies against gliadin (AGA-IgA), tissue transglutaminase (tTG-IgA), and endomysium (EMA-IgA) were analysed. RESULTS: Increased serum AGA-IgA levels were found in 411 of 428 CD cases, tTG-IgA in 385 of 428, and EMA-IgA in 383 of 428. In the control group, 11 of 216 had increased levels of AGA-IgA, 5 of 216 of tTG-IgA, and 8 of 216 of EMA-IgA. In CD children younger than 18 months, elevated AGA-IgA occurred in 97% and elevated tTG-IgA and EMA-IgA were found in 83% of the cases. Conversely, in CD children older than 18 months, elevated AGA-IgA occurred in 94%, and elevated tTG-IgA and EMA-IgA were found in 99% of the cases. CONCLUSIONS: In children older than 18 months, both tTG-IgA and EMA-IgA are sufficiently accurate to be used as a single antibody marker, whereas a large proportion of younger children with CD lack these antibodies. Therefore, when selecting children for small intestinal biopsy, the detection of a combination of AGA-IgA and tTG-IgA is optimal for identifying untreated CD in children younger than 18 months.

Prevalence of Celiac disease among children in Finland.

BACKGROUND: Wheat, rye, and barley proteins induce celiac disease, an autoimmune type of gastrointestinal disorder, in genetically susceptible persons. Because the disease may be underdiagnosed, we estimated the prevalence of the disease and tested the hypothesis that assays for serum autoantibodies can be used to detect untreated celiac disease and that positive findings correlate with specific HLA haplotypes. METHODS: Serum samples were collected from 3654 students (age range, 7 to 16 years) in 1994 and screened in 2001 for endomysial and tissue transglutaminase antibodies. HLA typing was also performed on stored blood samples. All antibody-positive subjects were asked to undergo small-bowel biopsy in 2001. RESULTS: Of the 3654 subjects, 56 (1.5 percent) had positive antibody tests, as determined in 2001. Results of the two antibody tests were highly concordant. As of 1994, none of the subjects had received a clinical diagnosis of celiac disease, but 10 who had positive tests for both antibodies in serum obtained in 1994 received the diagnosis between 1994 and 2001. Of the 36 other subjects with positive antibody assays who agreed to undergo biopsy in 2001, 27 had evidence of celiac disease on biopsy. Thus, the estimated biopsy-proved prevalence was 1 case in 99 children. All but two of the antibody-positive subjects had either the HLA-DQ2 or the HLA-DQ8 haplotype. The prevalence of the combination of antibody positivity and an HLA haplotype associated with celiac disease was 1 in 67. CONCLUSIONS: The presence of serum tissue transglutaminase and endomysial autoantibodies is predictive of small-bowel abnormalities indicative of celiac disease. There is a good correlation between autoantibody positivity and specific HLA haplotypes. We estimate that the prevalence of celiac disease among Finnish schoolchildren is at least 1 case in 99 children.

Prevalence and sensitization of atopic allergy and coeliac disease in the Northern Sweden Population Health Study.

BACKGROUND: Atopic allergy is effected by a number of environmental exposures, such as dry air and time spent outdoors, but there are few estimates of the prevalence in populations from sub-arctic areas. OBJECTIVE: To determine the prevalence and severity of symptoms of food, inhalation and skin-related allergens and coeliac disease (CD) in the sub-arctic region of Sweden. To study the correlation between self-reported allergy and allergy test results. To estimate the heritability of these estimates. STUDY DESIGN: The study was conducted in Karesuando and Soppero in Northern Sweden as part of the Northern Sweden Population Health Study (n=1,068). We used a questionnaire for self-reported allergy and CD status and measured inhalation-related allergens using Phadiatop, food-related allergens using the F × 5 assay and IgA and IgG antibodies against tissue transglutaminase (anti-tTG) to indicate prevalence of CD. RESULTS: The prevalence of self-reported allergy was very high, with 42.3% reporting mild to severe allergy. Inhalation-related allergy was reported in 26.7%, food-related allergy in 24.9% and skin-related allergy in 2.4% of the participants. Of inhalation-related allergy, 11.0% reported reactions against fur and 14.6% against pollen/grass. Among food-related reactions, 14.9% reported milk (protein and lactose) as the cause. The IgE measurements showed that 18.4% had elevated values for inhalation allergens and 11.7% for food allergens. Self-reported allergies and symptoms were positively correlated (p<0.01) with age- and sex-corrected inhalation allergens. Allergy prevalence was inversely correlated with age and number of hours spent outdoors. High levels of IgA and IgG anti-tTG antibodies, CD-related allergens, were found in 1.4 and 0.6% of participants, respectively. All allergens were found to be significantly (p<3 e-10) heritable, with estimated heritabilities ranging from 0.34 (F × 5) to 0.65 (IgA). CONCLUSIONS: Self-reported allergy correlated well with the antibody measurements. The prevalence of allergy was highest in the young and those working inside. Heritability of atopy and sensitization was high. The prevalence of CD-related autoantibodies was high and did not coincide with the self-reported allergy.

Low levels of IgM antibodies against phosphorylcholine-A potential risk marker for ischemic stroke in men.

BACKGROUND: Natural antibodies specific for phosphorylcholine (anti-PC) have been implicated as protective factors in atherosclerosis. We herein determined the relationship between IgM anti-PC and incidence of cardiovascular disease (CVD). METHODS: We studied 349 incident cases (200 men) of first events of CVD (coronary heart disease (CHD; n=203 or ischemic stroke; n=146) and 693 age- and sex-matched controls identified through 12 years of follow-up (1991-2003) of subjects from the cardiovascular cohort within the Malmö Diet and Cancer Study. Relative risks (RR) of CVD with 95% confidence intervals (CI) of incident CVD with adjustments for age, smoking, total cholesterol and blood pressure were determined. Anti-PC-levels were measured using ELISA (Athera CVDefine). RESULTS: As determined using Athera CVDefine, significant associations were attained with values of anti-PC below 17U/ml (corresponding to the lowest 9th percentile), which remained after taking confounders into account (RR: 1.79, 95% CI: 1.09-2.94, p=0.021). If men were studied separately, significance was evident at values below 17U/ml (RR: 2.01, 95% CI: 1.11-3.67, p=0.022), which was not the case among women. Furthermore, values below 17U/ml were also associated with ischemic stroke (RR=3.67, 95% CI: 1.34-10.1, p=0.01), but not with CHD. CONCLUSION: Low IgM anti-PC could be a novel risk marker for development of ischemic stroke in men. Further studies are needed to establish gender and subgroup differences.

Immunoglobulin G (IgG) anti-tissue transglutaminase antibodies used as markers for IgA-deficient celiac disease patients.

The role of immunoglobulin A (IgA) anti-tissue transglutaminase antibodies (IgA-tTG) as predictors of untreated celiac disease (CoD) is well documented, and the presence and levels of these antibodies are most accurately monitored with native or recombinant human antigens. However, IgA-deficient CoD patients are not identified by IgA serology, and conflicting results concerning the diagnostic validity of IgG antibodies against gliadin (IgG-AGA), endomysium (IgG-EmA), and tTG (IgG-tTG) have been reported. The aim of the present study was to evaluate the utility of IgG-tTG for the detection of CoD in IgA-deficient patients. Samples from 115 IgA-deficient and 200 IgA-sufficient subjects were collected and tested for the presence of IgA and IgG antibodies against tTG, EmA, and AGA. Antibodies against tTG were measured by an enzyme-linked immunosorbent assay based on recombinant human tTG, and antibodies against EmA were determined by immunofluorescence. The values for IgG-tTG showed a higher correlation (correlation coefficient [r] = 0.91) with those for IgG-EmA for the IgA-deficient subjects than for the IgA-sufficient subjects (r = 0.88). The overall concordance of the positive and negative results between IgG-tTG and IgG-EmA was 97%, and the IgG-tTG assay discriminated between IgG-EmA-positive and -negative subjects with IgA deficiency at a rate of 100%. Elevated levels of IgG-tTG and IgG-EmA were measured in 70% of the IgA-sufficient subjects. IgG-tTG detection with recombinant human tTG is a good alternative to IgG-EmA detection, and the addition of IgG-tTG assessment to present screening methods may improve the ability to identify IgA-deficient subjects with CoD.

Autoantibodies against soluble and immobilized human recombinant tissue transglutaminase in children with celiac disease.

OBJECTIVES: The conformation of tissue transglutaminase might influence the performance of immunoassays to detect autoantibodies from patients with celiac disease. The present study investigated how the exposure of tissue transglutaminase kept in a liquid phase and fixed to a solid support affected the binding of immunoglobulin (Ig)A and IgG autoantibodies in children with untreated and treated celiac disease. METHODS: Included were 73 untreated celiac disease children, 50 controls and 80 children with treated celiac disease. IgA and IgG antitissue transglutaminase were measured with solid phase enzyme-linked immunoassay (ELISA) and liquid phase radioligand binding assays. For IgG antitissue transglutaminase detection with radioligand binding assays antihuman IgG and protein A were used. IgA endomysial autoantibodies were measured by indirect immunofluorescence. RESULTS: Both ELISA and radioligand binding assays detected IgA antitissue transglutaminase in 65 of 73 untreated celiac disease children and in 2 of 50 controls. One additional control child was detected with radioligand binding assays. Endomysial autoantibodies were present in 62 of 73 celiac disease children and in 2 of 50 controls. IgG antitissue transglutaminase was detected with both ELISA and radioligand binding assays in 40 of 73 untreated celiac disease children and in 2 of 50 controls. Radioligand binding assays using protein A detected 20 of 73 additional untreated celiac disease children and one control child with increased IgG antitissue transglutaminase. In treated celiac disease children, 21 of 80 were IgA antitissue transglutaminase positive with radioligand binding assays, 3 of 80 with ELISA, whereas none had endomysial autoantibodies. CONCLUSIONS: No qualitative differences between radioligand binding assays and ELISA in IgA or IgG antitissue transglutaminase binding from untreated celiac disease children was demonstrated. However, discrepancies in the binding of IgA antitissue transglutaminase from a subgroup of treated celiac disease children indicated that alterations of tissue transglutaminase might occur on fixation of the antigen. Protein A used for radioligand binding assays seemed not to assess IgG autoantibodies exclusively. IgA antitissue transglutaminase detection in screening of childhood celiac disease can be performed either by ELISA or radioligand binding assays because the two assays are interchangeable.

Antitissue transglutaminase and antithyroid autoantibodies in children with Down syndrome and celiac disease.

OBJECTIVES: We measured circulating autoantibodies and evaluated the potential of circulating antitissue transglutaminase (tTG) antibodies to determine the presence of celiac disease (CD) in children with Down syndrome. METHODS: An ELISA based on recombinant human tTG was used to measure the levels of immunoglobulin A and immunoglobulin G antibodies in serum samples from 72 children with Down syndrome, 52 children with biopsy-verified CD, 21 disease controls with a normal small intestinal mucosa and 23 healthy controls. Of the 72 Down syndrome children, 11 under-went a small intestinal biopsy. RESULTS: Four of 72 children with Down syndrome were diagnosed as having CD and three of them had serum levels of immunoglobulin A tTG antibodies greater than 6 U/mL (668, 147 and 7 U/mL). One Down syndrome child with biopsyproven CD had normal levels of immunoglobulin A tTG. Two Down syndrome children had increased levels of immunoglobulin A tTG (13 and 7 U/mL) but none of these children had an intestinal biopsy performed. Of the 52 CD subjects (median 664 U/mL) one was negative for immunoglobulin A tTG (5 U/mL) and all healthy controls (median 1.2 U/mL) and disease controls (median 0.9 U/mL) had immunoglobulin A tTG antibody levels less than 6 U/mL. Two of four Down syndrome children with CD and 36 of 52 celiac children had increased serum levels of immunoglobulin G tTG antibodies. There was no correlation between the serum levels of tTG and antithyroid autoantibodies. CONCLUSIONS: Although the diagnosis of CD depends on histologic evaluation of intestinal biopsies, detection of anti-tTG antibodies provides a useful complementary diagnostic method for CD in children with Down syndrome.

Recombinant human tissue transglutaminase for diagnosis and follow-up of childhood coeliac disease.

Highly discriminatory markers for celiac disease are needed to identify children with early mucosal lesions and for rapid follow-up. The aim of this study was to evaluate the potential of circulating anti-tissue transglutaminase (tTG) IgA and IgG antibodies in the diagnosis and follow-up of childhood celiac disease. An ELISA using recombinant human tTG was used to measure the levels of IgA and IgG anti-tTG antibodies in 226 serum samples from 57 children with biopsy-verified celiac disease, 29 disease control subjects, and 24 healthy control subjects. All samples were also analyzed for anti-endomysium antibodies (EMA). The levels of IgA and IgG anti-tTG antibodies correlated with the condition of the small intestinal villous structure and the serum levels of IgA EMA. All of the 25 serum samples obtained from untreated patients contained IgA anti-tTG antibodies, and 24 of 25 also had IgA EMA. Of the serum samples from 53 control children, two had IgA anti-tTG antibodies and two had IgA EMA. Children younger than 5 y of age with untreated celiac disease had the highest serum levels of both IgA and IgG anti-tTG. There was already an increase in IgA anti-tTG antibodies after 2 wk of gluten challenge (p < 0.01). Although the criteria-based diagnosis of childhood celiac disease still depends on histologic evaluation of intestinal biopsies, detection of anti-tTG antibodies provides useful complementary diagnostic information. The human recombinant tTG-based ELISA can be used as a sensitive and specific test to support the diagnosis and may also be used in the follow-up of treatment in childhood celiac disease.