PROBLEM TO BE SOLVED: To provide a polypeptide for controlling an immune system directly in intestinal mucosa by clarifying indigenous bacteria species parasitized in large intestine mucosa indigenous cells and having mucosa immunomodulating activity, and a bacteria species-originated inducing factor, and to provide a method for producing the polypeptide, and an immunoregulation composition of large intestine mucosal tissue.SOLUTION: This large intestine mucosa immunoregulation polypeptide has a specific amino acid sequence, and an amino acid sequence in which one or a plurality of amino acids are substituted, deleted, inserted and/or added into the specific amino acid sequence, and brings about immunoregulation action in intestine mucosal tissue.