PRODUCTION OF ANTITRANSGLUTAMINASE AUTOANTIBODIES IN THE JEJUNUM OF PATIENTS WITH TYPE1 DIABETES

Abstract

Summary: An association between type 1 diabetes mellitus (T1DM) and celiac disease (CD) has been reported since a long time. The prevalence of CD in T1DM is as high as 1.3%-16.4%, and nearly 20% of T1DM children has been shown to react to rectal instillation of gliadin. A hallmark of CD are the autoantibodies to tissue transglutaminase (tTG). By the Phage Display technique we previously demonstrated that the site of production of tTGautoantibodies is the intestine. Aim: The aim of this study was to investigate the presence of IgA anti-tTG antibodies in jejunal biopsies from patients with T1DM patients who did not show serological markers of CD. Materials and Methods: We made antibody libraries from the jejuna of 7 patients with T1DM (4 EMA/tTG+, 3 EMA/tTG−). We first adopted the One Step Cloning Strategy: only the genes belonging to the VH5 family, which has been previously associated with the anti-tTG antibody response, were cloned. In a second stage the entire antibody repertoire from 2 EMA/tTG + and 2 negative was cloned. Results: The VH5 libraries from EMA/tTG + patients were highly positive for the presence of scFv anti-tTG, whereas those from EMA/tTG-patients were not. Surprisingly, the htTG selection of the complete antibody repertoire libraries revealed to be strongly positive also inpatients EMA/tTG−. The positive clones were subjected to BstnI restriction analysis (fingerprinting) and sequencing. The fingerprinting was highly variable and the sequencing showed that the scFv anti-tTG, in EMA/tTG-patients, belong prevalently to the VH3 gene family. A possible gluten-related condition was confirmed by the isolation of anti-gliadin scFv in EMA/tTG- patients. Conclusion: Phage Display libraries from T1DMpatients revealed the intestinal expression of anti-tTG antibodies also in absence of peripheral antibodies. T1DM patients EMA/tTG-produce anti-tTG antibodies prevalently with the VH3 gene family. It will be interesting to evaluate the percentage of T1DM patients EMA/tTG-producing intestinal anti-tTG antibodies and their possible progression toward an overt CD.