CXCL10 and COVID-19: Results from three independent scRNAseq studies using peripheral blood mononuclear cells from COVID-19 subjects revealed the Cxcl10 cluster correlated highest with (i) 10 genes in common to CD163hi Monocytes-Cohort 1-Cluster 2 in Schulte-Schrepping et al. [42] (P = 1.90E-15), (ii) nine genes in common to the severe COVID-19 up-regulated gene set in Lee et al. [44] (P = 2.3E-15), and (iii) six genes in common to CD16 Monocyte-Cluster28 in Wilk et al. [43] (P = 1.70E-07).