CCL2 and acute respiratory distress syndrome: While IL-13 was reported to be required for recovery after acute lung injury by regulating local levels of IL-6, CCL2/MCP-1, and G-CSF, IL-1β is usually known as a pro-inflammatory cytokine related to ARDS.45,46 However, other studies propose that IL-1β is involved in tissue healing and has beneficial effects on endothelial repair after ARDS.47 In addition, GM-CSF and VEGF are further factors elevated in Sub2 and significantly increased over time together with IL-1β and IL-13.