TLR4 and necrotizing enterocolitis: Although outside of the scope of this review, in addition to the TLR4 pathway, other pathways and cell types are thought to be important in the development of NEC including platelet-activating factor and macrophages (Caplan et al. 2005; Frost and Caplan 2013; Furukawa et al. 1993; Rabinowitz et al. 2001; Maheshwari et al. 2011; MohanKumar et al. 2016).