Enhancement of natural killer activity and IFN-γ production in an IL-12-dependent manner by a <i>Brassica rapa</i> L.

<p>Certain food components possess immunomodulatory effects. The aim of this study was to elucidate the mechanism of the immunostimulatory activity of <i>Brassica rapa</i> L. We demonstrated an enhancement of natural killer (NK) activity and interferon (IFN)-γ production in mice that were orally administered an insoluble fraction of <i>B. rapa</i> L. The insoluble fraction of <i>B. rapa</i> L. significantly induced IFN-γ production in mouse spleen cells in an interleukin (IL)-12-dependent manner, and NK1.1<sup>+</sup> cells were the main cells responsible for producing IFN-γ. Additionally, the results suggested that the active compounds in the insoluble fraction were recognized by Toll-like receptor (TLR) 2, TLR4, and C-type lectin receptors on dendritic cells, and they activated signaling cascades such as MAPK, NF-κB, and Syk. These findings suggest that <i>B. rapa</i> L. is a potentially promising immuno-improving material, and it might be useful for preventing immunological disorders such as infections and cancers by activating innate immunity.</p> <p>Active compounds in the insoluble fraction of <i>Brassica rapa</i> L. induces IFN-γproduction in a IL-12-dependent manner and enhancement of NK activity.</p>