XK and infection: The green fluorescent signals were relatively weak compared to WSN (Fig. 3c) in DCs co-cultured with mouse B cells labeled with 5(6)-carboxyfluorescein diacetate N-succinimidyl ester (CFSE) and infected with NA-defective WSN that had similar vRNA levels at 6-h post-infection to WSN-infected B cells (Fig. 3d), suggesting that the NA activity might affect the uptake of IAV antigens by DCs.