Single AF exposure led to marked cellular influx of neutrophils and eosinophils and increased Th2 cytokines. Eosinophilia persisted over 48 h after challenge, whilst neutrophils returned to normal. BALF SPD protein levels markedly increased 48 h after AF challengeSensitised mice that received rIL4 and rIL13 but not rIFNy increased SPD in BALFSPD production after AF challenge was absent in Stat6−/− versus WT controlsSPD production increased in response to IL4 and IL13 and was STAT6‐dependent. The gene discussed is IL4; the disease is atrial fibrillation.