In contrast, as shown in our earlier studies, monocyte- and neutrophil-recruiting chemokines (CCL2, CCL3, CCL4, CCL7, CCL8, CXCL1, CXCL2, CXCL3, and CXCL8) were highly expressed, whereas chemokines (CXCL9 and CXCL16) recruiting T cells were less expressed by monocyte-macrophages in BALFs of severe COVID-19 than those in mild cases (Fig. 3f). Here, CCL4 is linked to COVID-19.