ORAL BIOME AND AGING. “Immunosenescence results in increased bacterial load as cell-mediated and humoral immune responses wane. The innate immune system gradually takes over; contributing to the rise in circulating proinflammatory cytokines such as TNF. Maintaining the integrity of the blood-brain barrier (BBB) against a backdrop of increasing bacterial load is important.”
http://www.researchgate.net/profile/Deborah_Shoemark/publication/264794791_The_Microbiome_and_Disease_Reviewing_the_Links_between_the_Oral_Microbiome_Aging_and_Alzheimer’s_Disease/links/53fd9d340cf22f21c2f816ab.pdf