TLR4 and neurodegenerative disease: TLR4, which recognizes bacterial LPS by forming a complex with co-receptor CD14 and myeloid differentiation factor 2 (MD-2), is perhaps the best-studied of the TLRs, with numerous analyses implicating TLR4-dependent microglial activation in various scenarios of neuroinflammation and neurodegenerative diseases [121, 122].