Antimetastatic activity induced by Clostridium butyricum and characterization of effector cells.

The effects of a bacterial vaccine, heat-killed Clostridium butyricum MII 588 cells, on the metastasis of B16-F10 melanoma in BDF1 mice was investigated. The vaccine stimulated natural killer (NK) cell cytotoxic activity against YAC-1 target cells, which peaked at 72 hr after the pretreatment, whereas maximum macrophage cytotoxic activity was obtained on days 9 to 11. These stimulated cytotoxic activities were also observed in B16-F10 tumor-bearing BDF1 mice. The important role of stimulated NK cells and/or macrophage in the antimetastatic effect was confirmed using Anti-asialo GM1 antibody, whole body x-ray irradiation and carrageenan treatment. In addition, the vaccine could induce a high titer of interferon-gamma (IFN-gamma), an important lymphokine which may account for a significant portion of its antimetastatic activity.