CD4 and pulmonary emphysema: According to the significant role of autoimmunity in progressive emphysema, Taraseviciene-Stewart et al. [92] have found that nude rats injected intraperitoneally with human umbilical vein endothelial cells (HUVECs) could produce an antibody against ECs (anti-EC humoral response), which subsequently leads to the influx of CD4 lymphocytes into the lung, apoptosis of alveolar septal cells, activation of MMPs, and eventual emphysema.