SPP1 and COVID-19: To investigate if the in vitro SPP1-driven neutrophil cluster transcriptionally replicated any of the neutrophil phenotypes observed in severe COVID-19, we performed unsupervised mapping of the SPP1-driven neutrophil gene module (37 genes; Supplemental Data) into a whole-blood scRNAseq transcriptomic signature of healthy, mild, and severe COVID-19 (22).