To verify if A20 deficiency in myeloid cells affects IAV-induced gene expression in the lung, we analyzed the levels of several chemokines and cytokines in the bronchoalveolar lavage (BAL) at day 4, 7 and day 10 following infection. Levels of KC and MIP-2 chemokines, as well as IL-6 were significantly higher at day 7 p.i. in BAL from IAV infected A20myel-KO mice compared to IAV infected wild type mice (figure 3C). Unlike our observations with in vitro stimulated primary macrophages we could not detect a significant increase in MCP-1 or IFNα production in the lungs of A20myel-KO animals (figure 3C). KC is the murine orthologue of IL-8 and serves together with MIP-2 as a chemoattractant for neutrophils, while MCP-1 is mainly known as a chemoattractant for monocytes, which eventually develop into macrophages upon entering the alveolar lumen [60]. Consistent with the higher KC and MIP-2 levels in A20myel-KO mice, the number of neutrophils (CD11b+ Ly6C+ Ly6G+ F4/80−) that were recruited in the bronchoalveolar spaces upon IAV infection was clearly higher throughout infection in A20myel-KO mice compared to control animals (figure 3D). Although we could detect a significant increase in monocyte (CD11b+ Ly6C+) recruitment at day 4 post infection, this was not evident at later time points after infection (figure 3D), which is consistent with the equal expression of MCP-1 in both groups of mice. The number of resident alveolar macrophages (autofluorescent+ CD11c+ F4/80+ CD11b−) was also elevated in A20myel-KO mice but did not differ significantly between IAV infected or mock infected mice (figure 3D). Elimination of IAV infected cells depends on the clonal expansion of virus specific cytotoxic CD8+ T cells (CTL) [61], [62], [63]. To test whether A20 expression in myeloid cells regulates the antiviral CTL response, total CD8+ T cells and virus specific Granzyme B (GrB) and IFNγ expressing CD8+ T cells were measured in BAL and lung parenchyma of wild type and A20myel-KO mice. A clear increase in CD8+ T cells could be detected at day 7 and 10 post infection, but no differences were observed between A20myel-KO and wild type mice (figure S2A and figure S2C). Also, the number of GrB and IFNγ CD8+ T cells as well as IFNγ expression levels in the lungs were not altered by the absence of A20 in myeloid cells (figure S2A–C).