S100A9 and Alzheimer disease: Some components of the salivary multiprotein complex have already been characterized in our previous investigations on the salivary proteome of AD patients, such as S100A8, S100A9, and α-defensin 1, in addition to cystatin B. They had been found at significantly higher levels in the saliva of AD patients with respect to the healthy control group [14,15], while in the present study, non-significant variations were observed for these components.