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P014 Disruption of epithelial barrier function by coeliac peripheral blood mononuclear cells

D. Delbue da Silva1, A. Itzlinger1, B. Jessen1, H. Pfeiffert1, C. Heldt1, F. Branchi1, D. Lissner1, W. Dieterich1, B. Siegmund1, M. Schumann1

1Charité Universitätsmedizin, Department of Gastroenterology, Berlin, Germany

Background

Immune cells are present in the small intestine mucosa in normal and inflammatory conditions. Once activated, these cells cause direct effect in the barrier function of epithelial cells in inflammatory bowel diseases (IBD). It is known that the epithelial barrier function is altered in coeliac disease (CD), common disease affecting the small intestine. In CD patients, the immune cells in the small bowel mucosa are activated after contact with antigen-presenting cells exposing gliadin-derived peptides, which leads to an inflammatory cascade causing villous atrophy and disruption of the epithelial barrier. Nonetheless, the mechanisms underlying the disrupted barrier function in CD is not clearly understood. This study aimed to verify the effect of immune cells derived from coeliac patients on the barrier function of intestinal epithelial cells

Methods

Peripheral blood mononuclear cells (PBMCs) were isolated from the blood sample of heathy donors (n = 3), CD patients on gluten-free diet (CD GFD; n = 2) and active CD patient (n = 2). CacoBBe cells were co-cultered with PBMCs and CD14+ cells (monocytes). To verify the role of active gliadin stimulation, the intestinal cells were treated with or without IL15/Tglia. In addition, to exclude direct toxic effect of gliadin on the epithelium, control CacoBBe cells were treated with IL-15/Tglia alone. The integrity of the barrier in the monolayer cells was monitored by measuring transepithelial resistance (TER). The localisation of proteins with role in epithelial barrier function (CD71, occludin, claudin-2 and ZO-1) was investigated using confocal microscopy after immunostaining

Results

A more pronounced decrease in TER was observed in intestinal epithelial cells after co-culture with coeliac PBMCs and CD14+ cells (active CD or CD GFD patients) comparing with healthy donors. However, no difference in TER was observed comparing active CD and CD GFD. As found in completely untreated cells, in cells treated with IL-15/Tglia alone, the TER did not decrease. Exposure of intestinal epithelial cells to coeliac PBMCs resulted in a decreased expression of occludin, while no effect was observed in claudin-2 localisation and expression. In addition, it was observed an abnormal structure in ZO-1 after co-cultered epithelial cells with coeliac PBMCs (CD GFD and active CD). Confocal microscopy revealed an altered localisation of CD71 after treatment with coeliac PBMCs and CD14+ cells, with evidence of a diffuse intracellular localisation when compared with untreated cells.

Conclusion

Coeliac PBMCs have an effect on epithelial barrier function of intestinal epithelial cells. This is associated with an altered expression pattern of key proteins for tight junction assembly.