Further, several clinical investigations have revealed that chemokines such as IL-8, CCL2, CCL3, CCL7, CCL8, CXCL2, CXCL16, and CX3CL1 are infiltration signals that mediate the recruitment of mononuclear phagocytes to lungs (6, 240, 261, 263), and they are directly involved in the pathogenesis of severe clinical sequelae in COVID-19, including major complications that cause death in approximately 40% of severe COVID-19 cases (66, 68, 77, 261, 264). Here, CX3CL1 is linked to COVID-19.