Fusobacterium nucleatum‐mediated immunomodulation of the in vitro secondary antibody response to tetanus toxoid and Actinobacillus actinomycetemcomitans

The present study was undertaken to determine if one of the most prevalent periodontitis‐associated organisms, Fusobacterium nucleatum (F. NUC), was capable of modulating secondary immune responses, including responses against Actinobacillus actinomycetemcomitans (AA). Peripheral blood lymphocytes (PBLs) were obtained from individuals known to have high serum antibody against Tetanus toxoid (TT) or AA. The addition of either TT, sonicated F.NUC, or pokeweed mitogen (PWM) to PBLs from subjects with high anti‐TT titers stimulated production of anti‐TT in vitro. However, the addtion of TT in combination with either F.NUC or PWM resulted in dramatic enhancement of anti‐TT production over antigen or nonspecific activator alone. Similarly, an in vitro secondary response could be induced with antigen from AA, and the addition of F.NUC likewise showed a marked immunoadjuvant effect. The data indicate that F.NUC has potent immunomodulatory activity. The high titers of locally produced specific antibody in gingival crevicular fluid to AA and certain other periodontitis‐associated bacteria may result from the combined effect of specific antigen together with an immunomodulator of bacterial origin.