This invention provides an IFN inducer comprising, as an active ingredient, lactic acid bacteria and capable of inducing IFN production, an immunopotentiating agent or prophylactic agent against virus infection comprising such inducer, and a food or drink product comprising such IFN inducer and having IFN-inducing activity, immunopotentiating activity, or prophylactic activity against virus infection. The agent for inducing IFN production comprises, as active ingredients, lactic acid bacteria that can activate plasmacytoid dendritic cells (pDCs) and promote IFN production, such as Lactococcus garvieae NBRC100934, Lactococcus lactis subsp. cremoris JCM16167, Lactococcus lactis subsp. cremoris NBRC100676, Lactococcus lactis subsp. hordniae JCM1180, Lactococcus lactis subsp. hordniae JCM11040, Lactococcus lactis subsp. lactis NBRC12007, Lactococcus lactis subsp. lactis NRIC1150, Lactococcus lactis subsp. lactis JCM5805, Lactococcus lactis subsp. lactis JCM20101, Leuconostoc lactis NBRC12455, Leuconostoc lactis NRIC1540, Pediococcus damnosus JCM5886, or Streptococcus thermophilus TA-45.
