Abstract
Bifidobacteria are harbored in the intestine of specific animals and humans at different ages. In this study, we examined the immune responses affected by Bifidobacterium longum and B. animalis, focusing upon the cytokines produced by mouse peritoneal cells. Both B. longum and B. animalis induced the expression of IL-1β, IL-6, IL-10 and TNF-α mRNA in mouse peritoneal cells, as determined by RTPCR. The amount of IL-6 secreted by thioglycollate-induced peritoneal exudate cells (TG-PEC) in the presence of these bacteria were similarly augmented, as shown by ELISA. More TNF-α was induced in B. longum than in B. animalis. A difference in the level of TNF production was also suggested from the in vivo tumor suppression test using TNF-sensitive Meth A tumors, although both species of bacteria profoundly suppressed the tumor incidence and tumor growth. Taken together, both B. longum and B. animalis promote the induction and/or secretion of inflammatory cytokines (IL-6 and TNF-α) in mouse peritoneal cells. However, the level of TNF-α production induced by B. animalis was lower than that by B. longum.
