We subjected 48,583 PBMCs to Uniform Manifold Approximation and Projection (UMAP) using the Seurat package43 and identified clusters that are assigned to 11 different immune cell types, including CD14+ classical and intermediate monocytes, CD16+ cells, dendritic cells (DC), CD4 and CD8 T cells, NK cells, B cells, platelets, red blood cells and proliferative cells in healthy, mild COVID-19 and severe COVID-19 patients (Fig. 4a and b). The gene discussed is CD8A; the disease is COVID-19.