CCL2 and COVID-19: Although patients with severe COVID-19 have been found to have a cytokine storm in peripheral blood and bronchoalveolar lavage fluid [32,33], in lung parenchyma we only identified a small number of cytokine genes with differently major transcript usage, including IL1B, IL2, IL6ST, IL34, CCL2, CCL7, CMTM8, CSPG5, PDGFA, and PDGFRL (Figs 3D and S4).