The role of MyD88 signaling in heterosubtypic influenza A virus infections

► Lung and spleen CD4+ Th1 responses to heterosubtypic IAV infection were MyD88 dependent. ► Lung and spleen CD4+ T-cell frequencies were MyD88 independent. ► Th1 dependent IgG2c levels were partially dependent on TLR7 and MyD88 signaling. ► Lung CD8+ Th1 responses to heterosubtypic IAV infection were MyD88 independent. ► Spleen CD8+ Th1 responses and T-cell frequencies were MyD88 dependent.