CD4 and inflammatory response: Hence Foxo1 deletion may lead to the attenuation of IL-9-mediated SARS-CoV2 infection and associated lung inflammation. In line with this, our data demonstrated that Foxo1 deficiency in CD4+ T cells leads to blunted IL-9 production, which makes these mice less susceptible to SARS-CoV-2 infection and associated airway inflammation.