Abstract Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease affecting up to 10% of premature infants and characterized by an interleukin (IL)-17-driven uncontrolled inflammatory response. The goals of the proposed research are to identify the innate host defense responses in NEC pathogenesis and interrogate how these responses can be modified or prevented through dietary modifications. We have shown that breast milk mediates protection against NEC by inhibiting the pro-inflammatory signaling in the intestinal epithelium and we seek to determine the components of breast milk that mediate this anti-inflammatory effect. We now show that breast milk contains anti-inflammatory aryl hydrocarbon receptor (AhR) ligands, which have been shown to be critical for maintaining gut homeostasis by inducing expansion of innate lymphoid cells (ILC) and protective T helper (Th22) cells via IL-22 production. IL-22 signaling plays a critical role in attenuating intestinal inflammation, gut barrier function and promoting wound healing by facilitating intestinal stem cell regeneration. Importantly, these findings highlight the therapeutic potential of enhancing IL-22 production to attenuate pro- inflammatory responses seen in NEC. Therefore, we hypothesize that IL-22 producing cells play a protective role in NEC and that nutritional supplementation with AhR ligands will naturally induce intestinal IL-22 production, and inhibit the pathogenic IL-17 responses seen in NEC. To test this hypothesis, we will use our experimental NEC model and an ex vivo model of intestinal stem cell isolation and culture to pursue the following specific aims: Aim 1: To investigate the role of IL-22 producing cells in NEC pathogenesis. Aim 2: To determine the role of AhR signaling in NEC pathogenesis. These studies will advance our understanding of the signaling pathways involved in the pathogenesis of NEC and test the novel preventative nutritional strategy of manipulating anti-inflammatory cytokine production with dietary AhR ligands.