Western blotting indicated that there was a significant increase in TLR4 expression in SN samples from individuals with PD compared with age-matched controls (p = 0.005, Fig. 1c), even though there was no significant increase in the overall levels of Iba1 and OX-42 in the SN of patients with PD (Fig. 1c). Here, TLR4 is linked to Parkinson disease.