Interestingly, our in vivo finding demonstrating excessive neutrophil migration in lungs as a result of intratracheal rmOPN injection provided direct involvement of OPN-mediated induction of ALI (Figure 6A,B), which might in turn be reversed by administrating neutralizing Ab against OPN to attenuate lung neutrophil migration in sepsis-induced ALI. Here, SPP1 is linked to acute respiratory distress syndrome.