Interleukin-17A-producing γδ T cells drive cognitive dysfunction in periodontitis

Periodontitis, caused by the oral pathobiont Porphyromonas gingivalis (Pg), leads to progressive systemic diseases through oral-organ interactions, including cognitive dysfunction. However, the behavioral and immunological mechanisms underlying the oral-brain axis during the development of periodontitis remain unclear. We found that Pg-induced periodontitis promoted anxiety-like behavior and progressive cognitive dysfunction in mice. While Pg-induced periodontitis drove the accumulation of interleukin (IL)-17A-producing T cells in the mouth, an increased population of Vγ4⁺ γδ T cells migrate to the brain through the draining cervical lymph nodes via the CCL20/CCR6 pathway. Treatment with an anti-IL-17A antibody, an anti-CCL20 antibody, or anti-TCRγδ antibody ameliorated both anxiety-like behavior and cognitive dysfunction, and suppressed the increased expression of IL-17A receptor in the brain. Collectively, our findings reveal a function beyond its established role for IL-17A in the oral-brain axis that links Pg-induced periodontitis to cognitive dysfunction.