MADCAM1 and influenza: Since infected lungs do not express the alternative α4 integrin ligand MadCAM-1 (38) and NK cells express negligible α4β7 (Figure 3F), our results highlight a potential role of VLA-4-mediated NK cell interactions with VCAM-1 expressed by the peribronchial lung vessels during their entry into influenza infected WT lungs.