WT mice demonstrate reduced PXR expression and PXR−/− mice demonstrate a heightened inflammatory response following induction of experimental NEC. (a) Intestinal tissues from WT control (breastfed) and WT NEC mice (day 2 of the NEC protocol) immunostained for PXR. (b) Gross appearance of the intestine immediately after killing of WT or PXR−/− mice that were controls or subjected to the NEC protocol (day 2). (c) H&E-stained sections of the terminal ileum in the indicated groups. (d) Quantification of NEC severity in WT or PXR−/− mice. *P<0.05 when compared between the groups by unpaired t test. Results are representative of three separate experiments with 3 (for each control group) to 6 (for each group at day 2 NEC) mice per group. (e) qRT-PCR showing the levels of transcripts for IL-6 (i), TLR4 (ii), MUC2 (iii), and Cx43 (iv) relative to those for β-actin in intestinal tissues collected from WT or PXR−/− mice that were controls or subjected to experimental NEC. *P⩽0.05, **P⩽0.01, ***P⩽0.001 when compared between groups by unpaired t-test. Results are representative of three separate experiments with at least three mice per group. H&E, hematoxylin and eosin; NEC, necrotizing enterocolitis; PXR, pregnane X receptor; qRT-PCR, quantitative real-time PCR; TLR4, Toll-like receptor 4.