C5AR1 and COVID-19: Based on the fact that the pattern of expression of C5aR1 was mainly concentrated in myeloid cells (neutrophils and macrophages/monocytes) in the lung of patients with COVID-19 and SARS-CoV-2–infected Tg mice, we developed a colony of Tg mice lacking C5aR1 signaling (TgcKO mice) in these immune cells and infected them with SARS-CoV-2 (Supplemental Figure 7A).