Induction and Activation of Tumoricidal Cells In Vivo and In Vitro by the Bacterial Cell Wall of Bifidobacterium infantis

We measured the antitumor activity of Bifidobacterium infantis (B. infantis). We used mainly a cell wall preparation (WPG) based upon preliminary experiments (Cancer Res. 45: 1300-1307, 1985) . First, we evaluated the antitumor effects of WPG on peritoneal and thoracic tumor-bearing animals, using mouse Ehrlich carcinoma and Meth A fibrosarcoma, as well as rat MADB 106 mammary tumor. More frequent, earlier onset and dose-related injections of WPG were more effective in these tumor-bearing animals. Cell kinetic studies revealed that WPG induced polymorphonuclear cells (PMNs) followed by macrophages at the injection cavity. In addition, WPG directly activated these cells to inhibit the growth of tumor cells in in vitro assays. These results suggest that the bifidobacterial cell wall, WPG induces and activates nonspecific phagocytes (PMNs and macrophages) in situ to reject growing tumor cells in peritoneal and thoracic cavity of animals.