CXCR4 and COVID-19: Several of the chemokine receptors (e.g., CXCR3 and CXCR4) have also been shown to be upregulated during cytokine storm-like symptoms as upon binding of their natural ligands (e.g., CXCL12), inflammation is promoted and chemotaxis induces apoptosis potentially leading to significant tissue damage as seen in COVID-19 cases [39].