Human T‐cell responses to oral streptococci in human PBMC‐NOD/SCID mice

<jats:p>We investigated cellular and humoral immune responses to oral biofilm bacteria, including <jats:italic>Streptococcus mutans, Streptococcus anginosus, Streptococcus sobrinus</jats:italic>, and <jats:italic>Streptococcus sanguinis</jats:italic>, in NOD/SCID mice immunized with human peripheral blood mononuclear cells (hu‐PBMC‐NOD/SCID mice) to explore the pathogenicity of each of those organisms in dental and oral inflammatory diseases. hu‐PBMC‐NOD/SCID mice were immunized by intraperitoneal injections with the whole cells of the streptococci once a week for 3 weeks. FACS analyses were used to determine the percentages of various hu‐T cell types, as well as intracellular cytokine production of interleukin‐4 and interferon‐γ. Serum IgG and IgM antibody levels in response to the streptococci were also determined by enzyme‐linked immunosorbent assay. <jats:italic>S. anginosus</jats:italic> induced a significant amount of the proinflammatory cytokine interferon‐γ in CD4<jats:sup>+</jats:sup> and CD8<jats:sup>+</jats:sup> T cells in comparison with the other streptococci. However, there was no significant differences between the streptococci in interleukin‐4 production by CD4<jats:sup>+</jats:sup> and CD8<jats:sup>+</jats:sup> T cells after inoculation. Further, <jats:italic>S. mutans</jats:italic> significantly induced human anti‐<jats:italic>S. mutans</jats:italic> IgG, IgG<jats:sub>1</jats:sub>, IgG<jats:sub>2</jats:sub>, and IgM antibodies in comparison with the other organisms. In conclusion, <jats:italic>S. anginosus</jats:italic> up‐regulated Th1 and Tc1 cells, and <jats:italic>S. mutans</jats:italic> led to increasing levels of their antibodies, which was associated with the induction of Th2 cells. These results may contribute to a better understanding of human lymphocyte interactions to biofilm bacteria, along with their impact on dental and mucosal inflammatory diseases, as well as endocarditis.</jats:p>