IL22 and viral infectious disease: The expression of IL-22, which can assist in viral infection control, along with IFNs via IFN receptor signalling and STAT1-dependent pathways, was significantly downregulated in antibiotic-depleted chickens and was subsequently restored by treatment with probiotics or faecal microbiota transplantation (FMT), suggesting that IL-22-related mechanisms also take part in anti-H9N2 influenza immunity mediated by the intestinal flora.