Taking AD, a current medical research hotspot, as an example, Kamer et al. found that plasma concentrations of TNF-α and antibodies against periodontal bacteria Porphyromonas gingivalis, Tannerella forsythia, and Actinobacillus actinomycetemcomitans were obviously enhanced in AD patients compared to controls by ELISA technique [51]. Here, TNF is linked to Alzheimer disease.