To determine the impact of IFNλ during super-infection, we first elucidated general differences between C57BL/6 wild type (WT) and global IFNLR1 knockout mice using a 7 day super-infection model, where mice are inoculated with 900 plaque forming units (PFU) of mouse-adapted H1N1 strain A/PR/8/34 on day 0 and with 5 x 107 colony forming units (CFU) of Staphylococcus aureus on day 6 before harvesting 6 or 24 hours after bacterial infection (Fig 1A). Here, IFNLR1 is linked to bacterial infectious disease.