Polarization of Porphyromonas gingivalis-specific helper T-cell subsets byprior immunization with Fusobacterium nucleatum

Antigen-specific T-cell clones were obtained from mice immunized with Fusob acterium nucleatum ATCC 10953 and/or Porphyromonas gingivalis 381. 10 BALB/ c mice per group were immunized with F. nucleatum followed by P. gingivalis , or with P, gingivalis alone by intraperitoneal injection of viable microo rganisms. Spleen T cells were isolated and stimulated in vitro with viable P, gingivalis cells to establish P. gingivalis-specific T-cell clones. T-ce ll phenotypes and cytokine profiles were determined along with T-cell respo nsiveness to F. nucleatum? or P. gingivalis. Serum immunoglobulin G antibod y titers to F. nucleatum or P. gingivalis were also determined by enzyme-li nked immunosorbent assay, All the T-cell clones derived from mice immunized with F. nucleatum followed by P. gingivalis demonstrated Th2 subsets, whil e those from mice immunized with P. gingivalis alone demonstrated Th1 subse ts based on the flow cytometric analysis and cytokine profiles. All T-cell clones from both groups were cross-reactive to both P. gingivalis and F. nu cleatum antigens. Phenotypes of T-cell clones were all positive for CD4. Me an post-immune serum IgG antibody levels to F. nucleatum or P, gingivalis w ere significantly higher than the pre-immune levels (P<0.05, P<0.01, respec tively). There were no significant differences in the antibody titers betwe en the two groups. It was concluded that P. gingivalis-specific T cells ini tially primed by cross-reactive F. nucleatum antigens were polarized to Th2 subset, while T cells stimulated with P. gingivalis alone maintained the p rofile of Th1 subset.