Encapsulated Bifidobacterium bifidum potentiates intestinal IgA production.

We asked whether Bifidobacterium bifidum regulates the synthesis of IgA by mucosal lymphoid cells. B. bifidum alone, but not Clostridium perfringens, significantly induced total IgA and IgM synthesis by both mesenteric lymph nodes (MLN) and Peyer's patch (PP) cells. We, further, investigated the mucosal antibody production following peroral administration of B. bifidum to mice. Ingested B. bifidum significantly increased the number of Ig (IgM, IgG, and IgA) secreting cells in the culture of both MLN and spleen cells. Nonetheless, B. bifidum itself does not induce the own specific antibody responses, implying that B. bifidum does not provoke unnecessary immune reaction. Subsequently, it was found that encapsulation of B. bifidum further augments the total IgA production in the culture of both MLN and spleen cells. Finally, we found that the immuno-stimulating activity of B. bifidum is due to its cellular components but not due to any actively secreting component(s) from bacteria.