Effects of Actinomyces and Fusobacterium on humoral immune response in vitro

The purpose of this study was to examine the effects of Actinomyces viscosus and Fusobacterium nucleatum sonicates on antibody formation in vitro and to elucidate their mechanisms on the cellular basis. Suspensions of A. viscosus and F. nucleatum were sonicated, and the supernatant was filtered and heated. After AKR mouse spleen cells were stimulated with sheep red blood cells, the antibody formation was assayed by counting the plaque-forming cells (PFC). Macrophages, T- and B-cells were harvested from the mouse peritoneal exudate and spleen. Mitogenicity of the sonicates was determined by counting the uptake of ³H-thymidine.
The PFC number, when A. viscosus or F. nucleatum sonicate was added, increased significantly by 2.4–6.6 times more than the control. Two sonicates were found to activate the macrophages, resulting in an increase of PFC.
F. nucleatum sonicate was effective to PFC response via activation of helper T-cells. Stimulation index of F. nucleatum sonicate on T-cells was 4.1 and that of A. viscosus sonicate on B-cells was 3.2. In conclusion, the enhanced antibody formation by A. viscosus sonicate depends on the activation of macrophages and B-cell mitogenicity, and the F. nucleatum sonicate enhances the PFC response by activation of both macrophages and helper T-cells and by T-cell proliferation.