We have identified an abundance of this FCGR3B upregulated monocyte-derived alveolar macrophage cell population (cluster 11 marked by CCL3L1) in multiple tissue data sets of respiratory samples from severe COVID-19 single-cell and bulk transcriptomes, while this cell population was absent in moderate COVID-19 and control samples (Figure S4). Here, CCL3L3 is linked to COVID-19.