Bacterial DNA is such an immunostimulatory microbe-associated ligand,whose properties can be mimicked by oligodeoxynucleotides (ODN) containing unmethylated cytosine-guanine dinucleotides in specific base sequences (CpG motifs).Bifidobacteria,which are genetically distinct from typical lactic acid bacteria although they are generally classified into lactic acid-producing bacteria,have a high GC content of 55 to 67%.Several studies have shown that Bifidobacterium was able to activate immune cells such as macrophage,natural killer and B cells.However,the specific functional sequences with immtme modulatory activity have not been characterized yet.