CSTB and neurodegenerative disease: Due to the relevance of developing proteomic studies in peripheral biofluids to the AD-associated biomarker discovery and the known ability of cystatin B to interact in multi-protein complexes [24,25,26,27] and considering the significance of PPI studies in the field of neurodegenerative disease, we decided to investigate the possible PPI of cystatin B in AD saliva.