Toll-like receptor 4-MD-2 complex (TLR4-MD-2)

The Toll-like receptor 4-MD-2 complex is a heterodimeric pattern recognition receptor complex found on the surface of immune cells such as macrophages and dendritic cells. It consists of Toll-like receptor 4 (TLR4) and its co-receptor myeloid differentiation factor 2 (MD-2), which together recognize and bind lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls. Ligand binding triggers a dimerization event, initiating intracellular signaling via both MyD88-dependent and -independent (TRIF-dependent) pathways, ultimately resulting in the production of pro-inflammatory cytokines and type I interferons. The TLR4-MD-2 complex plays a central role in the innate immune response, activation of adaptive immunity, and contributes to host defense against infection, but its dysregulation is implicated in a variety of pathological conditions including sepsis, chronic inflammation, cancer, and neurodegenerative disorders[6][7][9][5][1][2][3]. Pharmacological modulation of this complex is of therapeutic interest, with both agonists (as vaccine adjuvants) and antagonists (for the treatment of sepsis and other inflammatory diseases) under investigation[7][2][8].

Other names

TLR4/MD-2 complexToll-like receptor 4/myeloid differentiation factor 2 complexTLR4–MD-2

Agonists (e.g., LPS, MPLA) bind and induce dimerization/activation of the TLR4-MD-2 complex, triggering intracellular pro-inflammatory signaling cascades via MyD88- and TRIF-dependent pathways[2][7][3][5][9]. Antagonists (e.g., Eritoran, Resatorvid) block ligand binding or receptor dimerization, thereby preventing downstream signaling[7].