However, it is important to note that while we have shown that IL-21R signaling was not required for clearance of primary IAV infection, IL-21R signaling has been shown to play a critical role in the generation of CD8+ T cell and B cell memory during viral infection, thus likely plays an important role in pathogenesis and virus clearance after secondary IAV infection [4,23]. This evidence concerns the gene IL21R and viral infectious disease.