In line with in vivo research, in vitro data focusing on human DCs provided supportive evidence for the application of PDE4 inhibitors in ALI/ARDS because of their capacity to restrain DC maturation [123,124,125], Th1/Th17 polarization and secretion of crucial inflammatory mediators [6,63,64,65,66]. This evidence concerns the gene PDE4A and acute respiratory distress syndrome.