Activation of RANKL-induced osteoclasts and memory T lymphocytes by Porphyromonas gingivalis is serotype dependant

Abstract

Aim: Destructive periodontitis is associated with a Th1–Th17 immune response and activation of RANKL-induced osteoclasts. In addition, Porphyromonas gingivalis K1 and K2 serotypes induce a strong Th1–Th17 response. This study aimed to investigate whether these P. gingivalis serotypes induce higher osteoclasts activation, by increased Th17-associated RANKL production, and an antigen-specific memory T-lymphocyte response. Material and Methods: The RANKL production and TRAP+ osteoclast induction were quantified on na€ıve T lymphocytes stimulated with dendritic cells primed with the P. gingivalis serotypes. The T-bet, GATA-3, RORC2 and Foxp3 expression was correlated with RANKL production. The frequency of proliferating memory T lymphocytes in response to P. gingivalis serotypes was determined in both periodontitis and healthy subjects. Results: T lymphocytes stimulated by K1 or K2-primed dendritic cells elicited higher levels of RANKL and TRAP+ osteoclasts than cells stimulated with the other serotypes. RANKL positively correlated with RORC2. Whereas periodontitis patients had a higher frequency of memory T lymphocytes responding to K1 or K2, healthy subjects had a higher frequency of memory T lymphocytes responding to K4 or K . Conclusions: P. gingivalis serotypes K1 and K2, but not others, are associated with an increased production of the osteoclastogenesis-related factor RANKL. This important information suggests that these serotypes could elicit a greater bone resorption in vivo and have a role in the periodontitis pathogenesis.