Interestingly, all the differentially expressed inflammation-related proteins, complement proteins (C1Q, C9, C1B, C1C, C4B, C4A, CFHR1, and C1S), and interferon-gamma receptor 1 were increased, clearly showing that the activated complement proteins are one of the potential main causative factors of PD (supplemental Data S2). This evidence concerns the gene C4B and Parkinson disease.