CCL4 and COVID-19: We found upregulation of proinflammatory cytokines consistent with previous findings in severe COVID-19.25 By comparing cytokine profiles in the PBMC, lung and BALF samples, we found that levels of proinflammatory cytokine transcripts, such as interleukin 6 (IL6), tumor necrosis factor (TNF), CXC-chemokine ligand 10 (CXCL10), CC-chemokine ligand 2 (CCL2, also called MCP-1 or monocyte chemotactic protein 1), CCL3 and CCL4, were much higher in the BALF and lung samples than in the PBMC sample, which is consistent with the pathological focus of severe COVID-19 in the lung parenchyma.26