Enhancement of cytotoxic activity of lymphocytes in mice by oral administration of peptidoglycan (PG) derived from Bifidobacterium thermophilum.

: A preparation of peptidoglycan (PG) of Bifidobacterium thermophilum (B. thermophilum) of swine was orally administered to SPF-C57BL/6CrSlc mice in order to confirm the enhancement of the cytotoxic activity of natural killer cells (NK), intraperitoneal cytotoxic T lymphocytes (CTL) and lymphocytes stimulated by concanavalin A (Con A-stimulated lymphocytes). The NK cells from the spleen and the mesenteric lymph node (MLN) of mice that were continuously fed with PG-mixed feed for three weeks showed a significantly higher rate of cytolysis than those from the control group. However, a single oral administration of PG had no significant effect on NK activity. The activity of peritoneally sensitized CTL of the mice that were continuously fed with PG-mixed feed was assayed. The PG-mixed feed administered group showed a higher CTL activity than that of the control group. The cytotoxic activity of Con A-stimulated lymphocytes in the PG-mixed feed administered group was higher than that of the control group. These results indicate that the cytotoxic activity of mice was enhanced by orally administered PG.