Microbiota is not only for the eliciting of effector immune responses by stimulating the production of various proinflammatory cytokines such as interferon gamma (IFN-γ) during infection but also for the establishment of an immunotolerant microenvironment by contributing to the generation of immunoregulatory cells such as regulatory T (Treg) cells to maintain homeostasis (45, –, 47). Here, IFNG is linked to infection.