CXCR4 and acute respiratory distress syndrome: Previous reports have suggested that both the CXCR3 and CXCR4 axis play a pivotal role in the prolonged recruitment and/or retention of immune cells in ALI/ARDS, exerting a damaging effect in the lung (Petty et al., 2007; Nie et al., 2008; Kelsen et al., 2009).