The complement system in COVID 19: friend and foe?
COVID 19, the disease caused by severe acute respiratory syndrome coronavirus 2 (SARS CoV 2) has resulted in a global pandemic and a disruptive health crisis. COVID 19 related morbidity and mortality has been attributed to an exaggerated immune response. The role of complement activation and its contribution to illness severity is being increasingly recognized. Here, we summarize current knowledge about the interaction of coronaviruses with the complement system. We posit that: (a) coronaviruses activate multiple complement pathways; (b) severe COVID 19 clinical features often resemble complementopathies; (c) the combined effects of complement activation, dysregulated neutrophilia, endothelial injury, and hypercoagulability appear to be intertwined to drive the severe features of COVID 19; (d) a subset of patients with COVID 19 may have a genetic predisposition associated with complement dysregulation; and (e) these observations create a basis for clinical trials of complement inhibitors in life threatening illness.
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