Background
Celiac disease(CeD) is characterized by the presence of highly specific autoantibodies against transglutaminase2(anti-TG2), which are produced in the small intestinal mucosa and can be detected both in mucosal tissue and serum. Serum anti-TG2 antibodies typically disappear on gluten-free diet. Interestingly, spontaneous disappearance of anti-TG2 despite continued gluten consumption has been reported in a subgroup (around one-third) of children with potential celiac disease (PCD). Whether this phenomenon reflects restoration of immune tolerance to gluten and disappearance of gluten-specific T cells remains unknown. Here, we investigated the functional activity and regulatory profile of intestinal T cells in PCD children with spontaneously lost CeD-specific autoantibodies.
Methods
Four pediatric patients with PCD(mean age 5.5 years, range 5.4–6.0) who became seronegative over time (at least 4 negative anti-TG2 determinations in 2 years) and on gluten containing diet were enrolled. Short-term T-cell lines (iTCLs) were established from gut biopsies by stimulating with deamidated gliadin(dGlia). Antigen-specificity was assessed against dGlia and DQ2-restricted immunodominant peptides by IFN-γ-ELISA. Regulatory pathways were analyzed by using neutralizing anti-IL-10R and anti-TGFβ antibodies.
Results
Gliadin-specific CD4+ T-cell lines were successfully generated from all patients, demonstrating the presence of gluten-reactive, IFN-γ secreting T cells. Both dGlia and peptides stimulation induced IFN-γ secretion (mean fold increase 61,23±112 and 317,84±190, respectively) which markedly increased following IL-10R/TGFβ blockade (mean 113±198 and 766,81±1325 respectively), indicating that gluten-specific effector responses are actively restrained by IL-10 and TGFβ-mediated immunoregulatory pathways.
Conclusions
We demonstrated that spontaneous anti-TG2 disappearance does not reflect loss of gluten-specific T-cell immunity. Gluten-specific, IFN-γ-secreting T cells infiltrate intestinal mucosa and are actively regulated by immunosuppressive mechanisms involving IL-10 and TGFβ. Further longitudinal immunological studies are required to assess the natural history of these peculiar PCD patients, to shed light if spontaneous disappearance of serum anti-TG2 represents a state of immune regulation or an immune tolerance acquisition.