TNF and COVID-19: PAI-1 concentration was also increased in influenza-infected mice.40 In humans, severe influenza infection is, like COVID-19, associated with ARDS and elevated levels of pro-inflammatory cytokines, chemokines, and endothelial factors like IL-6, TNFα, CXCL8, CXCL10, and HGF.41,42 These results argue for a crucial role of the endothelial integrity in several severe virus infections and, thus, indicate that endothelial cells could serve as a therapeutic target.