To determine the immune cell types involved in the differential expression of MCEMP1, HLA-DRA and ETS1, we leveraged on a single cell transcriptome data of peripheral blood mononuclear cells (PBMCs) (GSE149689) that was performed on healthy controls (n = 4), and patients with mild COVID-19 (n = 4) and with severe COVID-19 (n = 6).42 The gene discussed is HLA-DRA; the disease is COVID-19.