CXCR4 and acute respiratory distress syndrome: The ligand acting within its pathway is MIF and the receptors are CD74,CD44 and CXCR4, the ligand-receptor pair that plays a major role is MIF-(CD74+CXCR4) (Figure 7Q), whereas the mouse data analyzed shows that MIF-(CD74+CD44) plays a major role in the extra-pulmonary ALI mice.