IL1B and Hepatitis: Recent studies have shown that mRNA expressions of multiple pro-inflammatory and immune cytokines, such as IFN-γ, IL-2 [63], IL-1β, IL-6, IL-8, TNF-α [64,65], IFNs, Mx and OASL [46], increased significantly in the hypervirulent FAdV-4-infected chicken tissues; and our unpublished data also demonstrated that compared with non-pathogenic strains, hypervirulent FAdV-4 infection triggered severe liver inflammation and significantly increased expression level of IL-1β in serum, suggesting that these molecules were positively correlated with tissue damage.