Abstract: The mice were given oral administration of a large anount of Bifidobacteriun bifidim for a long time. Significant anounts of anti-B.bifidum antibody were detected in the serum.However, in mice administratd Salmonella sp.,the antibody were detected in much higher level in a short time.These results suggest that the enormus numbers B.bifidim were hard to induce serim antibody production. Even if some antibody was produced the level was rather low, and quickly decreased- Furthermore, in vitro test, the optimal dose of B.Bifidum used to induce antibody production by spleen lymphocyte was 20 times than that of Sal. sp. .Thus, the study showed that B.bifidum was a weakly immunogenic antigen.

Key words: Bifidobacterium bifidum Immunogenicity