In addition, serine protease HtrA1 [32], prostaglandin-H2 D-isomerase (also termed lipocalin-type prostaglandin D synthase/β-trace) [33], apolipoprotein D [34], thrombospondin-4 [35], cystatin-A [36], glia-derived nexin [37], complement factors C3 and C9 [38-41], and the proteoglycan decorin [42] colocalize with β-amyloid plaques in Alzheimer disease. This evidence concerns the gene C9 and Alzheimer disease.