Both TLR2 and TLR4 levels were increased in the blood, gut, and brain tissues of PD patients (Drouin-Ouellet et al., 2014; Dzamko et al., 2017; Perez-Pardo et al., 2019), suggesting an association between TLRs and neuroinflammation in the disease process of PD. This evidence concerns the gene TLR4 and Parkinson disease.