KLK4 and COVID-19: By virtue of its ability to bind and activate (29, 42, 43) two of the most potent inflammatory systems in plasma–the complement system and the kinin-kallikrein system (KKS)–we hypothesized that cell surface expressed or secreted gC1qR could also contribute to the rapid inflammatory response and the “cytokine storm” that is associated with COVID-19 pathology.