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Background & Aims Variants in the genes ATG16L1 and IRGM affect autophagy and are associated with the development of Crohn's disease. It is not clear how autophagy is linked to loss of immune tolerance in the intestine. We investigated the involvement of the immunologic synapse—the site of contact between dendritic cells (DCs) and T cells, which contains molecules involved in antigen recognition and regulates immune response. Methods DC autophagy was reduced using small interfering RNAs or pharmacologic inhibitors. DC phenotype and function were analyzed by confocal microscopy, time-lapse microscopy, and flow cytometry. We also examined DCs isolated from patients with Crohn's disease who carried the ATG16L1 risk allele. Results Immunologic synapse formation induced formation of autophagosomes in DCs; the autophagosomes were oriented toward the immunologic synapse and contained synaptic components. Knockdown of ATG16L1 and IRGM with small interfering RNAs in DCs resulted in hyperstable interactions between DCs and T cells, increased activation of T cells, and activation of a T-helper 17 cell response. LKB1 was recruited to the immunologic synapse, and induction of autophagy in DC required inhibition of mammalian target of rapamycine signaling by the LKB1–AMP activated protein kinase (AMPK) pathway. DCs from patients with Crohn's disease who had an ATG16L1 risk allele had a similar hyperstability of the immunologic synapse. Conclusions Autophagy is induced upon formation of the immunologic synapse and negatively regulates T-cell activation. This mechanism might increase adaptive immunity in patients with Crohn's disease who carry ATG16L1 risk alleles.

OP03 Induction of autophagy upon DC-T cell contact is mediated by LKB1 AMPK mTOR signalling M.E. Wildenberg1 *, A.C. Vos2, M. Duijvestein2, A. Verhaar3, G. van den Brink4, D.W. Hommes5. 1Academic Medical Center, Tytgat Institute for Intestinal and Liver Research, Amsterdam, Netherlands, 2Leiden University Medical Center, Gastroenterology-Hepatalogy, Leiden, Netherlands, 3Leiden University Medical Center, Leiden, Netherlands, 4Academic Medical Center, Gastroenterology & Hepatology, Amsterdam, Netherlands, 5UCLA, Division of Digestive Diseases, Los Angeles, United States

food resuspended in physiological salt solution. Foods scoring positive in skin tests were tested. A drop was placed on the lower lip and left for 10 seconds to 2 minutes. The result was read 15 minutes late. Positive reactions in LFT can be divided into five types: (1) smoothing of the lower lip; (2) erythema under the lip; (3) contiguous rash of the cheek and chin; (4) edema of the cheek associated with rhinitis and watering eyes; and (5) systemic reaction associated with itching of the areas affected by eczema and coughing. Results: A total of 406 LFT were performed, 314 of which were positive and 92 negative, followed by positive food challenges. The foods provoking reactions were egg white (140 cases), peanut (80 cases), cow’s milk (79 cases), cod (8 cases), kiwi (4 cases), shrimp (3 cases). The LFT positivity was mostly (88.7% of cases) manifested as a labial edema with contiguous urticaria. There were systemic reactions in 4.6% of cases: generalized urticaria, hoarnseness and rapid-onset and generalized eczema. The 92 infants with negative labial food test results had positive food challenges. The reactions were in 66 cases generalized urticaria, 20 cases asthma attacks, 2 cases generalized eczema, and in 2 cases general anaphylaxis shock. The sensitivity of LFT was 78%. Conclusions: The LFT was easy to perform with children. Positive results indicate the presence of food allergy, but negative results require further investigations preferably double-blind, placebo-controlled food challenge. Further comparative analyses of the LFT and oral food challenge will better determine the value of the LFT for the exploration of cases of food allergy.