TLR4 and necrotizing enterocolitis: The mechanism by which AHR activation in the intestinal epithelium attenuates NEC severity involves a reduction in signaling and expression of the innate immune receptor TLR4, whose expression is elevated in the premature bowel as compared with the full term bowel5,9, and whose activation on the intestinal epithelium we have shown to be critical for NEC development4,5,27.