CCL4 and COVID-19: Differential gene expression analysis showed that in comparison to moderate patients, CD4+ T-cells from severe COVID-19 patients expressed higher levels of the AP-1 genes FOS, FOSB, and JUN, the activation marker MKI67 (Ki67), Th2-related genes IL4R and MAF, and chemokines including CCL2, CCL3, CCL4, CCL7, CCL8, and CXCL8 (Figure 1D, Supplementary Figure 1B).