FCGR2A and COVID-19: The binding of such SARS-CoV-2 IgM-ICs to FcμR and SARS-CoV-2 IgG1-ICs/GC-specific IgG1-ICs to activating FcγR, and the direct binding of SARS-CoV-2 to mannose-binding lectin (MBL-MASP 1-2) lead to the massive production of C5a in patients with COVID-19 and GD patients with COVID-19 (Figure 1A,B).