CXCL6 and COVID-19: As notable difference, strong induction of neutrophil-recruiting chemokines targeting CXC chemokine receptor (CXCR) 2, such as CXCL1, CXCL3, CXCL6, and CXCL8, were found only in human basal and secretory cells with severe COVID-19 but were absent in moderately-ill Syrian hamsters (Supplementary Fig. 6a, Fig. 3).