Screening for the Immunopotentiating Activity of Food Microorganisms and Enhancement of the Immune Response by Bifidobacterium adolescentis M101-4

The ability for such lymphocyte activation as growth of the spleen and Peyer’s patch (PP) cells from unprimed BALB/c mice, and of lymph node (LN) cells from mice immunized with hen’s egg ovomucoid (OM) was assayed by using sonicated microorganisms. The occurrence of immunopotentiating activity was strikingly dependent on the properties of individual strains, rather than on the species or microbial culture conditions. All the tested Bifidobacterium strains, especially B. adolescentis M101-4, showed strong mitogenic activity in those assays, and also enhanced the production of the anti-OM antibody by LN cells, while they did not induce the growth of thymocytes. Similar results were obtained from experiments using germ-free (GF) mice. These results suggest that the activation with B. adolescentis M101-4 was not due to any secondary stimulation of lymphocytes primed with bacteria in the gut or environment, but to direct or indirect activity toward B cells that was intrinsic to the strain.