Augmentation of natural killer cell activity in vitro and in vivo by sericin-derived oligopeptides

Abstract

This study investigated the effects of sericin-derived oligopeptides on natural killer (NK) activity. In vitro exposure of human peripheral blood mononuclear cells with sericin-derived oligopeptides resulted in an augmentation of NK cell activity against K562 target cells and the effects appeared to be dose-related. Experiments designed to examine whether enhanced NK activity was due to direct or indirect activation of NK cells revealed that sericin oligopeptides did not induce activity of purified NK cells, and that sericin oligopeptides augmented NK activity indirectly by inducing the production of IL-2 and IFN-γ cytokines. In in vivo experimentation where mice were orally administered with sericin oligopeptides and splenic mononuclear cells tested against YAC-1 target cells, significant increase in NK activity was obtained compared to control mice. Elevated levels of IL-2 were also evident in all oligopeptides-treated groups. As demonstrated both in vitro and in vivo, these results indicate that sericin-derived oligopeptides have efficient NK-enhancing activity and suggest the potential therapeutic applications of such oligopeptides for functional improvement of NK cells, and possibly for treatment of tumor and infectious diseases in which NK activity contributes to host defense.