Satu Sulkanen

Tissue transglutaminase autoantibody enzyme-linked immunosorbent assay in detecting celiac disease

BACKGROUND & AIMS Tissue transglutaminase has been reported to be the target for endomysial antibodies in celiac disease. We sought to establish whether immunoglobulin (Ig) A class tissue transglutaminase autoantibodies can be considered specific for celiac disease. METHODS Serum samples from 136 patients with untreated celiac disease (diagnosed according to the criteria of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition) and 207 disease controls were studied. Enzyme-linked immunosorbent assay (ELISA) and Western blots were performed using calcium-treated and untreated tissue transglutaminase as antigen. Reticulin, endomysial, and mouse monoclonal tissue transglutaminase antibodies were studied by an indirect immunofluorescence method and gliadin antibodies with ELISA. RESULTS The calcium-activated tissue transglutaminase autoantibody ELISA was highly sensitive (129 of 136) and specific (194 of 207) in detecting celiac disease. The new autoantibody ELISA test correlated well with the endomysial antibody test. Tissue transglutaminase autoantibody ELISA showed a clearly better predictive potential than the IgA class gliadin antibody ELISA. Immunoblots and ELISA blocking studies showed that calcium is needed for the specific antigen-antibody reaction to occur. Double immunofluorescence staining in human umbilical cord with sera from patients with celiac disease and with monoclonal tissue transglutaminase antibodies showed complete overlap. CONCLUSIONS Calcium-activated tissue transglutaminase autoantibody ELISA is highly accurate in detecting untreated celiac disease. Tissue transglutaminase seems to be the target self-antigen for endomysial antibodies.

IgA-class transglutaminase antibodies in evaluating the efficacy of gluten-free diet in coeliac disease

Objective Serum IgA-class tissue transglutaminase antibody has proved effective in screening for coeliac disease. The response to a gluten-free diet has been assessed on the basis of small-intestinal morphology. We investigated whether the tissue transglutaminase antibody test could substitute biopsy in this respect, and whether the test is better than the endomysial antibody test in follow-up. Design Controlled cross sectional, and follow-up study. Methods Serum IgA-class tissue transglutaminase antibodies and endomysial antibodies were determined in 87 coeliac adults on a gluten-free diet. All underwent small bowel biopsy, and the mucosal morphology was interpreted along with Marshs grading 0–3. In 30 patients histological and serological data could be analysed before and after adopting the diet; Marsh 3 was considered inadequate mucosal recovery during the diet. Results Of the 87 coeliac patients 27 showed Marsh 3 villous atrophy on gluten-free diet; of these 27, tissue transglutaminase antibody was within normal limits in 16 (59%) and endomysial antibody in 20 (74%). Two (7%) out of 29 with normal mucosa (Marsh 0) had positive tissue transglutaminase antibodies. Six (55%) out of 11 admitting regular dietary lapses remained tissue transglutaminase antibody negative. In the follow-up, serum IgA-class tissue transglutaminase antibody was initially positive in 28 (93%) out of 30 untreated patients; even a significant decrease in tissue transglutaminase antibody did not guarantee mucosal recovery. Conclusions A substantial number of coeliac patients with negative tissue transglutaminase or endomysial antibodies may still have manifest mucosal villous atrophy. Small bowel biopsy is therefore still necessary to ensure that the gluten-free diet is adequate.

Antibodies in Relation to Gluten Intake

Serum reticulin, endomysial and gliadin antibody tests are used in serological screening and case finding of coeliac disease, as well as the novel tissue transglutaminase antibody test. None of these tests are 100% predictive, however. Reticulin/endomysial antibodies predict forthcoming coeliac disease in individuals with normal small-bowel mucosal morphology. The effect of a gluten-free diet can be monitored with serological tests. A positive test result often indicates an inadequate gluten-free diet. However, slight dietary transgressions and minor mucosal damages cannot always be revealed with the serological tests. Therefore, small-bowel mucosal biopsy remains the most sensitive method to monitor the effect of a gluten-free diet.

Autoantibodies in celiac disease: importance of fibroblasts.

BACKGROUND Serum reticulin and endomysium autoantibodies are highly celiac disease-specific, and the autoantigens have been shown to be derived from human fibroblasts. Among human tissues, the umbilical cord also expresses these antigens. This study was conducted to compare different autoantibody tests and especially to elucidate whether human umbilical cord is a suitable substrate in tests and whether the cord jelly-derived fibroblasts express the antigens. METHODS The indirect immunofluorescence method was used to detect the tissue and Whartons jelly-derived fibroblast antibodies in 334 celiac disease and control sera samples. Affinity chromatography studies were used to show the correlation between human fibroblast-derived autoantigens and tissue and gliadin antibodies. The jelly-derived fibroblasts were used as antigen in a whole-cell enzyme-linked immunosorbent assay. RESULTS Celiac disease patient sera showed IgA-class human umbilical cord antibody with high sensitivity (100%) and specificity (99%). All celiac disease patient sera tested showed in indirect immunofluorescence the molecules expressed by Whartons jelly-derived fibroblasts. The whole-cell fibroblast autoantibody enzyme-linked immunosorbent assay had a sensitivity of 100% and a specificity of 81%. Human fibroblast-derived celiac disease autoantigens absorbed most of the IgA responsible for human umbilical cord antibodies but not the IgA responsible for gliadin antibodies in the same sera. CONCLUSIONS Whartons jelly-derived fibroblast autoantibodies tested in a novel whole-cell enzyme-linked immunosorbent assay correlated well with the human umbilical cord but not with gliadin antibodies.