CS and viral infectious disease: After mild inflammatory stimulation or viral infection, AT2 cells can present antigens to T cells to initiate T cell responses (29) and maintain alveolar function by increasing citrate synthase expression, upregulating the expression of the mitochondrial biogenesis–related gene PPARGC1A (PGC-1α), and promoting mitochondrial apoptosis and other approaches for maintaining alveolar function (30).