CCL4 and COVID-19: An alveolar macrophage sub-population characterized by increased secretion of CCL8, CXCL10, CXCL11, and IL-6 and a blood monocyte sub-population characterized by increased secretion of IL-1β, CCL20, CXCL2, CXCL3, CCL3, CCL4, and TNFα were found in the BAL of severe COVID-19 patients (n = 38) or patients that were characterized by a severe progression of COVID-19 (n = 54) [120].