TLR4 and coinfection: The TAK-242/siRNA-treated IAV+SA group exhibited markedly decreased mRNA levels of inflammatory factors (NF-κB, IL-6, TNF-α) and adhesion molecules (ICAM-1, VCAM-1) compared with the uninfected IAV+SA group, confirming TLR4 as the key receptor mediating co-infection-induced inflammation.