CD4 and acute respiratory distress syndrome: At 3 days after mMSCs transplantation, the number of CD4+ T cells in the lungs increased significantly in the LPS + mBM-MSC, LPS + mBM-MSC-NC, and LPS + mBM-MSC-TGFβ1 groups compared with that in the ARDS group (p < 0.05, Fig. 4a).