Periodontitis is one of the severe oral diseases that threatens both the oral and general health of humans. It is an inflammatory disease caused by the complex interaction between the plaque microorganisms and the host immune system. The innate immune response is activated when pathogens invade the periodontium. An excessive innate immune response leads to inflammation and the destruction of periodontal tissues, which then activates the adaptive immune response. Although systemic initial therapy and guided tissue regeneration (GTR) can control periodontal inflammation to a certain extent and promote periodontal tissue regeneration, their effects are still limited. Periodontal treatment will be significantly improved if it is possible to screen the potential therapeutic targets and regulate the key molecules involved in periodontal disease; however, relevant research on the prevention and treatment of periodontitis remains limited. Thus, with the aim of assisting the immunoregulation of periodontitis, this article summarises the cells and mechanisms involved in the innate immune response and adaptive immune response caused by pathogens in the periodontium. Keywords: adaptive immune response immune cells, inflammation, innate immune response, periodontitis