TNF and Alzheimer disease: Research on mice has shown that periodontopathogenic A. actinomycetemcomitans OMVs not only promote TNF-α secretion by human macrophages in the periodontium but also pass through the blood‒brain barrier (BBB) to increase TNF-α levels in the brain, contributing to the progression of neuroinflammatory disorders such as AD (Figure 5D).156