Fig. 1

Abnormal activation of complement interacts with pro-inflammatory cells, cytokines, coagulation and thrombotic microangiopathy mechanisms during the SARS-CoV-2 infection. The abnormal activation of complement after SARS-CoV-2 infection interacts with pro-inflammatory cells, cytokines, coagulation and thrombotic microangiopathy mechanisms, leading to the generation of cytokine storms. Cytokine storms cause lymphopenia, immune paresis, secondary infection, multiple organ failure and even death, which are more prominent in critically ill patients with COVID-19