The mouse OX40L‐mediated influenza A viral infection was further confirmed by in vitro and in vivo blocking studies with the monoclonal antibody to mouse OX40L; the in vitro pretreatment of OX40L‐expressing MDCK cells and the in vivo treatment of influenza‐infected mice with anti‐mouse OX40L antibody resulted in abrogated viral nucleoprotein expression and survival advantage, respectively (P < 0.05 to control antibody, Fig 4F; P < 0.05 to control antibody, Fig 4G). This evidence concerns the gene TNFSF4 and influenza.