To assess whether the protective effects of breast milk for NEC required AHR, we supplemented infant formula with human breast milk and observed a reduction in NEC severity in wild-type mice but almost no protection by breast milk on NEC in Ahr-/- mice, as revealed by the lack of reduction in histology and NEC severity score (Fig. 5h, i), or the expression of Il6 (Fig. 5j) and Tnf-α (Fig. 5k), or Tlr4 (Fig. 5l). This evidence concerns the gene TLR4 and necrotizing enterocolitis.