CD4 and acute respiratory distress syndrome: • TNF, IL-1b, and IL-6 increase trypsin production breaking down matrix metalloproteinases and increasing tissue permeability• IFNγ production by Th1 cells is essential for antiviral immunity• IL-6 can reduce Th1 polarization by initiating CD4+ cell differentiation into Th2 cells or reducing IFNγ production• IL-6 promotes Th17 cell growth and IL-17A release, activating Bcl-XL• IL-17 increases neutrophil movement and viability, causing ARDS