IL6 and COVID-19: Indeed, severe COVID-19 is characterized by a marked increase in the production of proinflammatory cytokines such as interleukin-6 (IL-6), interferon-γ (IFN-γ), and IL-17, diminished antiviral type I and type III interferon (IFN) responses, increased immune cell exhaustion and decreased cytotoxicity (3, 6, 7).