Autoimmune diseases (AIDs) are polygenic diseases affecting 7–10% of the population in the Western Hemisphere with few effective therapies. Here, we quantify the heritability of paediatric AIDs (pAIDs), including JIA, SLE, CEL, T1D, UC, CD, PS, SPA and CVID, attributable to common genomic variations (SNP-h²). SNP-h² estimates are most significant for T1D (0.863±s.e. 0.07) and JIA (0.727±s.e. 0.037), more modest for UC (0.386±s.e. 0.04) and CD (0.454±0.025), largely consistent with population estimates and are generally greater than that previously reported by adult GWAS. On pairwise analysis, we observed that the diseases UC-CD (0.69±s.e. 0.07) and JIA-CVID (0.343±s.e. 0.13) are the most strongly correlated. Variations across the MHC strongly contribute to SNP-h² in T1D and JIA, but does not significantly contribute to the pairwise rG. Together, our results partition contributions of shared versus disease-specific genomic variations to pAID heritability, identifying pAIDs with unexpected risk sharing, while recapitulating known associations between autoimmune diseases previously reported in adult cohorts.

Background. Clostridium difficile infection is associated with pediatric inflammatory bowel disease (IBD) in several ways. We sought to investigate C. difficil

Dendritic cells (DC) are key players in intestinal immunity, as these cells can direct the immune response to either a tolerogenic or an immunogenic phenotype. In the intestine, DC sample and process luminal antigens by protruding dendrites through the epithelial cell layer. At the same time barrier integrity is maintained through the continuous formation of tight junctions. Aberrations in these interactions may lead to altered antigen sampling and improper immune responses. We have recently shown that autophagy, a process implicated in the pathogenesis of Crohn's disease, regulates cellular interactions in the context of DC and T cells. In this study we aimed to determine whether autophagy also regulates DC-epithelial cell interactions and whether this influences the ensuing immune response. DC were generated from peripheral blood monocytes of healthy volunteers. For interaction studies, DC were co-cultured with intestinal epithelial cells on the baso-lateral side of a transwell insert. Modulation of autophagy was achieved using atg16l1 specific siRNA or pharmacological inhibitors. Intraepithelial protrusion of dendrites was determined by confocal microscopy. Luminal sampling and DC activation status were analyzed by flow cytometry. Protein expression was measured by immunoblotting and cytometric bead assay. Adhesion molecules E-cadherin and occludin partly localized to autophagosomes and increased autophagy resulted in decreased levels of these proteins. Reduced autophagy in either DC, epithelial cells or both resulted in the decreased formation of transepithelial protrusions by DC as well as a reduction in antigen sampling. Moreover, when autophagy was inhibited in the co-culture model, DC expressed increased levels of HLA-DR and costimulatory molecule CD86. Furthermore, decreased levels of autophagy resulted in lower IL-10 production by DC and these cells induced significantly more T-cell proliferation in an allogeneic mixed lymphocyte reaction. In intestinal DC-epithelial cell interactions, autophagy deficiency leads to decreased antigen sampling, increased DC maturation and a more pro-inflammatory type of DC.