Whereas the difference in Tlr4 (Fig. 3h) and a decrease in jejunal Tlr2 (−53%, Supplementary Fig. 3i) were the only significant changes conferred by IL-37 when we compared the two NEC groups, we unexpectedly found that the presence of IL-37 altered TLR expression in the intestines of control mice: There was an up to 3.4-fold increase in Tlr5-7, Tlr9, and Tlr11-13 mRNA abundance (Fig. 3i–o, significant for Tlr5, Tlr7, Tlr9, and Tlr13) in IL-37tg compared to WT dam-fed mice. Here, TLR4 is linked to necrotizing enterocolitis.