IL6 and COVID-19: It is noted that an increased release of pro-inflammatory cytokines by Th1 and Th17 cells (e.g., IL-6 and IL-17) was observed in COVID-19 patients, associated with the hyperinflammatory conditions (42, 43), high-dose IVIg has been shown to inhibit the activation, and subsequent production of cytokines by Th1 and Th17 cells in several clinical studies and in vitro experiments, and further reconstruct the balance between Th1, Th2, Th17, and Treg cells (44–47).