CD4 and acute respiratory distress syndrome: To further characterize the cell-specific influence of P2X7R-signalling in the pathogenesis of ALI/ARDS, we repeated the experiments with conditional P2X7Rfl/fl mice crossed with CD4-Cre animals (lymphocytes), LysM-Cre animals (macrophages/neutrophils) and CCT-Cre animals (airway epithelial cells).