IFNG and infection: In microbiota-depleted or Cx3cr1−/− mice, the serum IFN-γ level failed to increase to an adequate level similar to that in WT mice during infection (Figure 1c, Figure S1c, see online supplementary file), whereas in butyric acid-pretreated microbiota-depleted mice, the serum level of IFN-γ was elevated.