2008 年 56 巻 4 号 p. 199-208
There have been numerous evidences indicating that milk proteins influenced various immune functions. Here, we review the milk proteins playing the important roles. Recent reports have shown that LF enhanced anti-microbial, anti-viral and anti-tumor immune activities when orally administered. We report here that orally administered bovine LF (bLF) increases peripheral NK cell and augments the NK cell activity. Oral administration of bLF immediately induced the production of IL-18 in the intestinal epithelium, and the elevation of portal IL-18 levels. Furthermore, oral bLF administration augmented the expression of type-I IFNs in Peyer's patches and mesenteric lymph nodes. Collectively, these results indicated that orally administered bLF stimulated intestine-associated immune functions, including the production of IL-18 and type-I IFNs, and then raised the NK cell activity.
All classes of immunoglobulin are found in milk. Human milk antibodies are primarily of the secretory IgA type, while the major antibodies of bovine milk are IgG type. Secretory IgA consists of two molecules of IgA bound to a protein, the secretory component. Human milk contains secretory IgA antibodies against microorganisms which have exposed the mother's gastrointestinal and respiratory tract.
Milk contains a number of other proteins participating in defense in addition to lactoferrin and antibodies. Lactoperoxidase has a wide range of biological functions including antimicrobial and immuno-modulatory effects. Lysozyme which cleaves peptidoglycans of bacterial cell walls achieves a bactericidal effect.