Previous studies have suggested that the cell type-specific host immune response to P. gingivalis infection is closely linked to the activation of pattern recognition receptors (PRRs).54 NODs are a group of intracellular pattern-recognition proteins that recognize invading pathogens and induce host responses to limit bacterial infection.55 In the present study, P. gingivalis upregulated the expression of NOD1 but not NOD2. The gene discussed is NOD1; the disease is bacterial infectious disease.