AIF1 and Parkinson disease: Moreover, immunofluorescence staining confirmed the increase in TLR4 expression observed by western blotting, and further demonstrated that TLR4 was mainly localized within Iba1-positive cells (marked with yellow arrows, Fig. 1d), suggesting that there was a significant increase in microglial TLR4 in the SN of patients with PD compared with age-matched controls.