IL21 and infection: In summary, our studies demonstrated pIRES-ragB-mGITRL injection in mice dramatically decreased the lesion size, and inhibited the development of infection by P. gingivalis. Further mechanisms studies revealed that pIRES-ragB or pIRES-ragB-mGITRL injection significantly enhanced the proliferation of Tfh and IFN-γ+ T cells by GITR/GITRL system, inducing a large number of cytokines such as IFN-γ and IL-21, and thus promoted the production of RagB-specific antibody.