CCL2 and COVID-19: In agreement with this study, scRNA-seq data of nasopharyngeal and bronchial samples from 19 COVID-19 patients revealed the presence of inflammatory non-tissue resident and monocyte-derived macrophages expressing various cytokines, including IL1, TNF, CCL2 and CCL3, as well as enhanced interactions between epithelial and immune cells as determined by ligand–receptor expression profiling, in critical compared to moderate disease (31).