IL2 and COVID-19: The cytokine storm syndrome of severe COVID-19 is characterized by high circulating levels of interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-7 (IL-7), interleukin-10 (IL-10), interleukin-17 (IL-17), granulocyte-macrophage colony-stimulating factor (GM-CSF), C-X-C motif chemokine ligand 10 (CXCL10), C-C motif chemokine ligand 2 (CCL2), C-C motif chemokine ligand 3 (CCL3), and tumor necrosis factor (TNF) (Table 1) (Huang and others 2020).