IL6 and Alzheimer disease: Similarly, the infections by P. gingivalis increased productions of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), IL-6, and IL-1β, as well as complement factors, nitric oxide (NO) and reactive oxygen species, which augmented Aβ deposits and activated complement system, causing inflammation, brain tissue degeneration, and cognitive impairment, consistent with the damage in AD (Boje and Arora, 1992; Floyd, 1999; Liccardo et al., 2020; Costa et al., 2021).