NK-3 Immune 250mg with Vitamin C, 30 Capsules, Source NaturalsNK 3 Immune Supports Natural Killer Cell Activity. Available with vitamin C or with selenium. NK 3 Immune with Vitamin C supports numerous natural immune processes, activating the work of macrophages, T cells, B cells, and natural killer or NK cells, the body's "first line of defense." It stimulates the production of the chemical messengers that activate the body's natural immune response and it also supports a healthy circulatory system. Supplement