TLR4 and necrotizing enterocolitis: Myeloid differentiation protein 2 (MD2) is upregulated in the LPS/TLR4 signaling pathway in NEC patients and activates downstream effectors like NF-κB, a key player in the proinflammatory response [34-36]. MD2 is a glycoprotein that is involved in the LPS recognition by toll-like receptors.