For example, IL-22 was found to be induced in vivo by bacterial infections in rainbow trout (Harun et al., 2011; Monte et al., 2011; Chettri et al., 2012), turbot (Costa et al., 2012), pompano (Peng et al., 2017) and catfish (Jiang et al., 2018), by vaccination (Veenstra et al., 2017), and by stimulation with PAMPs and recombinant cytokines (IL-1β and TNFα) (Veenstra et al., 2018; Wangkahart et al., 2019b). This evidence concerns the gene IL22 and bacterial infectious disease.