To study the role of tyrosine phosphorylation in influenza A virusinduced inflammasome activation we infected human macrophages in the presence and absence of PP2 which is a highly specific inhibitor of src tyrosine kinases. PP2 completely inhibited infuenza A virus Udorn/72-and Beijing 353/89-induced IL-18 secretion ( Fig. 5F and Fig. S3D, respectively) . Furthermore, PP2 also abrogated IL-1b secretion in response to influenza A virus infection (Fig. 5G) demonstrating that influenza A virus-induced inflammasome activation is dependent on src family tyrosine kinase activity. 