SPDL1 and acute respiratory distress syndrome: To assess the therapeutic effectiveness of sPD-L1 mRNA-MC3-LNPs, we administered i.v. injections of PBS, PD-L1-Fc protein (0.8 mg/kg), Luc mRNA-MC3-LNPs (0.2 mg/kg), and sPD-L1 mRNA-MC3-LNPs (0.2 mg/kg) four hours after intratracheally administering PAO to induce ARDS.