FIGURE 1.

Roles of Interleukin‐6 produced by endothelial cells in inflammation and immune responses in the course of SARS‐CoV‐2 infection. Epithelial cell infection via the ACE2 receptor induces the production of cytokines and chemokines that activate proximal endothelial cells (EC). Activated EC strongly up‐regulate their expression of IL‐6, a pleiotropic alarm signal, which contributes to the development of immune responses (via direct signaling) and also to further inflammation after binding soluble IL‐6R. IL‐6 together with tissue and induced cytokines and chemokines such as CCL2 activate and recruit blood leukocytes. Activated and differentiated cells infiltrate infected tissues and target viruses and infected cells. Failure to eliminate the virus, to down‐regulate cytokine and chemokine expression and to limit tissue damage will result in amplification loops of inflammatory responses with increased endothelial permeability and further recruitment of activated immune cells. IL‐6 and soluble IL‐6R (red arrows) appear as major targets for therapeutic intervention