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

Abstract

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.

FIG. 1.

A and B: Jejunal section from a subject without celiac disease. It is a negative sample. In A, IgA deposits (in green) are detected only inside plasma cells, whereas tissue transglutaminase (in red) is evident around the crypts and in the subepithelial area. B: Confocal analysis with a scatter plot of the image. In this plot, no area of colocalization is evident around the diagonal of the Cartesian graphic. C and D: Jejunal section from a type 1 diabetic patient with a high serum level of anti-TG2 autoantibodies. In C, IgA deposits (in yellow-orange) are present in a patchy distribution in the subepithelial area and around mucosal vessels. These IgA/anti-TG2 antibody colocalization areas have been analyzed by confocal microscopy. The related scatter plot is shown in D, and the image of this area of colocalization is represented by orange dots. E and F: Jejunal section from a patient with untreated celiac disease with positive serum anti-TG2 antibodies and EMAs, in which thick IgA anti-TG2 antibody deposits are evident just under the superficial epithelium and around the vessels (E). This subepithelial area has been studied by confocal microscopy, and the related scatter plot (F) shows an extensive area of IgA deposits/TG2 colocalization. (A high-quality digital representation of this figure is available in the online issue.)

FIG. 2.

Percentage of VH gene family usage in the recombinant anti-TG2 antibodies selected from seven intestinal B lymphocytes of type 1 diabetic patients (T1DM) and three intestinal B lymphocytes of patients with celiac disease.

FIG. 3.

Monkey esophagus sections stained with anti-TG2 scFv containing a VH1, VH3, and VH4 gene segment. An anti-TG2 VH5 scFv is shown as a control. All of the scFvs recognize native TG2–anti-endomysium structures in the oesophagus muscularis mucosa according to the reticular motif, which is similar to the results observed for serum anti-endomysium antibodies. (A high-quality digital representation of this figure is available in the online issue.)