CD274 and acute respiratory distress syndrome: While many current studies focus on the PD-1:PD-L1 pathway in T-cell immunoregulatory responses, our laboratory has demonstrated that expression of PD-1 contributes to mortality in our murine model of hemorrhagic shock (Hem) priming for the development of indirect acute respiratory distress syndrome (iARDS) following a subsequent septic challenge (CLP) (6, 7).