The secretion of IL-17 was above the detection limit of the assay in eight of 23 intestinal biopsy samples from CD patients, but in none of five reference samples. We examined the apoptotic effects of IL-17 on Caco2-cells in vitro, alone or in combination with TNF-α, which is known to be apoptotic for epithelial cells. IL-17 receptor A mRNA transcripts were highly expressed in CaCo-2 cells (Ct was 24 for IL-17RA and 13 for 18S; n = 8). Furthermore,

incubation with IL-17 increased the transcription of the anti-apoptotic gene bcl-2 but did not up-regulate the expression of BAX, which is activated in the apoptosis (Fig. 4). We did not find evidence supporting an up-regulation of intestinal IL-17 immunity in T1D-related intestinal inflammation or in potential CD, but in CD the IL-17 response was linked to untreated CD characterized find more by villous atrophy and IL-17

immunity was down-regulated after GFD. Our results check details point out that up-regulation of mucosal IL-17 immunity is seen at the late stage of CD, when villous atrophy has developed. We found up-regulation of IL-17 immunity only in children with untreated CD, as demonstrated in independent patient series from Finland and Sweden. Elevation of duodenal IL-17A transcripts was observed and the small intestinal biopsies of untreated CD patients seemed to spontaneously secrete more IL-17A in vitro compared to reference children. However, the numbers of IL-17-positive cells in Finnish children with untreated CD were not increased significantly compared to reference children. This might indicate up-regulation of Il-17A production without remarkable expansion of Th17 cells at the time of villous atrophy. Our findings of the effect of GFD on the normalization of intestinal IL-17 up-regulation is in agreement with Italian studies showing an association of mucosal IL-17 activation in untreated but not in GFD-treated CD [23,24]. We also studied healthy children with and many without

TGA, and showed that up-regulation of IL-17 immunity does not occur in children with TGA, who are at high risk of CD and are considered as having potential CD. In potential CD the inflamed intestinal mucosa is characterized by increased numbers of γ/δ T cells and up-regulation of the IFN-γ pathway. Accordingly, our findings in children with potential CD indicate that wheat gliadin induced mucosal inflammation, which is already present in potential CD, does not include IL-17 immunity. Our findings of the activation of IL-17 immunity at only a late stage of the disease could explain the discrepant reports of IL-17 secretion by gliadin-specific T cells [12,25]. Bodd et al. showed that T cells reactive to deamidated gliadin do not secrete IL-17 [12]. A recent study, however, reported that gliadin-specific Th17 cells are present in the mucosa of untreated CD patients [25].