Additionally, increased levels of TNF-α in the systemic circulation of AD patients has been related to the presence of periodontopathogenic microorganisms (i.e., Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Porphyromonas gingivalis) as well as the antibodies against such pathogens (Kamer et al., 2009; Olsen et al., 2016). The gene discussed is TNF; the disease is Alzheimer disease.