Mucosal tissue transglutaminase expression in celiac disease

Abstract

Tissue transglutaminase (tTG) plays an important role in celiac disease pathogenesis and antibodies to tTG are a diagnostic marker of gluten-sensitive enteropathy. The aim of this study was to investigate the localization of tTG in the duodenal mucosa in control tissues and in different histological stages of celiac disease by using a commercial and a novel set of anti-tTG monoclonal antibodies, to see whether this assessment can be useful for diagnostic purpose. The distribution of tTG was firstly evaluated in 18 untreated celiac patients by using a commercial monoclonal antibody (CUB7402) against tissue transglutaminase enzyme and directed against the loop-core region of the enzyme. Thereafter, in further 30 untreated celiac patients we employed three newly characterized anti-tTG monoclonal antibodies produced against recombinant human-tTG. The epitopes recognized are located in three distinct domains of the protein corresponding to the core, C1 and C2 protein structure. Eleven age- and sex-matched patients with chronic duodenitis acted as controls. All subjects underwent upper endoscopy to obtain biopsy samples from the duodenum. Overall, we found that (i) tTG is equally expressed in CD at different stages of disease; (ii) tTG is expressed, at similar level, in CD and controls with duodenitis. Assessment of tTG level in biopsy samples by immunohistochemical methods is not useful in the clinical diagnostic work-up of CD.

1

The arrows show positivity for tTG under the superficial epithelium of villi with CUB 7402 in a case of initial lesion (A) and total atrophy (B) (paraffin fixed biopsy, original magnification ×100). (C) (original magnification ×40) and (D) (original magnification ×20) show frozen biopsies.

2

The arrows show positivity for tTG under the superficial epithelium of villi with CUB 7402 on paraffin fixed (A, original magnification ×20) and frozen biopsy (B, original magnification ×100).

3

The arrows show the staining patterns of the three new mAbs in paraffin fixed sections. The figures above show initial lesions, the figures below show atrophic lesions. (A) and (D) mAb 1, (B) and (E) mAb 2, (C) and (F) mAb 3 (original magnification ×100).

4

The arrows show positivity for the Paneth cells with mAb 3 (paraffin fixed biopsies, original magnification A ×40, B ×100).

5

Expression of CD31 (A) and mAb 3 (B) on consecutive sections (original magnification x20).

6

The arrows show positivity for IgA in plasma cells of the basal part of lamina propria (original magnification A ×20, B ×40).