Consistent with this finding that the OX40L‐promoted influenza infection depended on the sialylation, forced expression of human OX40L led to a significant increase in not only the viral plaques, but also the surface sialic acid residues in α‐2,6 linkage to the underlying sugar, the structure that enables the influenza A virus to attach and enter the host cells (P < 0.01, Appendix Fig S7; P < 0.005, Fig 5B and C). Here, TNFSF4 is linked to influenza.