MPO and COVID-19: The complex bidirectional interaction between neutrophils and cytokines make NETosis a likely mediator for severe symptoms that can be seen in response to SARS-CoV-2 infection, and in fact increased level of MPO-DNA that is associated with NETs was recently found in serum from COVID-19 patients (Zuo et al., 2020) and that plasma MPO-DNA complex levels increase with COVID-19 illness severity (Middleton et al., 2020).