IL33 and bacterial arthritis: ST2 deficiency improves the outcome of Staphylococcus aureus-induced septic arthritis using the intraarticular infection model [34]; in a systemic infection model induced by a lethal intravenous dose of S. aureus, IL-33 administration protects against lethality via ILC2-dependent type 2 cytokine production [35]; in post-influenza S. aureus pneumonia, IL-33 diminishes bacterial loads and mortality by an effect that does not require ILC2 cells [36].