NK-9 Immune System Support for dogs helps provide unsurpassed support for a dog's immune system, especially their NK cells - a type of white blood cell known as the immune system's front-line of defense. NK-9 contains AHCC (Active Hexose Correlated Compound), which has been shown to support the immune system in more than 20 published studies and in clinical experience with both humans and dogs. NK-9 is "the" AHCC product specifically formulated for dogs.