TLR4 and pneumonia: Some of the main active ingredients have been reported to have direct antiviral effects or to reduce pneumonia by suppressing inflammation; for example, isoliquiritigenin reduced influenza virus-induced lung inflammation and mortality in mice (Traboulsi et al., 2015), luteolin suppressed coat protein I complex expression to decrease the yield of IAV in vitro (Yan et al., 2019), and kaempferol exhibited a protective effect on H9N2 virus-induced inflammation via the suppression of the TLR4/MyD88-mediated NF-κB and MAPK pathways (Zhang et al., 2017).