Our proteome data showed that the proteins negatively correlated with MMSE scores had strong enrichment in the complement activation pathway, suggesting a strong complement inflammatory response in the peripheral system; however, only slight increase of the complement activation pathway proteins (SERPINA1, C4BPA, C8A, C8G, SERPINF2, C1S, and C4BPB) were detected in MCI and AD patients. This evidence concerns the gene C1S and Alzheimer disease.