S100A8 and COVID-19: In COVID-19 subjects, and consistent with the earlier single-cell analysis49, Silvin et al.50 reported the presence of a novel monocyte cluster (cluster “hMono3”) that expressed a set of neutrophil-associated genes, including S100A8/S100A9 and colony-stimulating factor 3 receptor (CSF3R); the latter being an essential growth factor receptor for polymorphonuclear phagocytes.