TLR9 and Parkinson disease: TLR2, TLR9, and TLR4, which binds LPS explicitly, are the most important in PD; downstream, they use myeloid differentiation primary response protein 88 (MyD88) or the TIR-domain-containing adaptor-inducing interferon-β (TRIF) pathway to initiate proinflammatory cytokines IL-1, IL-6, and TNF-α synthesis [116].