Cytokine storm and the prospects for immunotherapy with COVID-19.

Knowledge about the pathobiology of SARS-CoV-2 as it interacts with immune defenses is limited. SARS-CoV-2 is spread by droplets that come into contact with mucous membranes. COVID-19 is characterized by 2 or 3 stages: most patients who recover experience 2 stages of illness commencing with an asymptomatic or paucisymptomatic incubation period, followed by a nonsevere symptomatic illness lasting for several weeks, occurring in about 80% of those infected. In the remainder, a third phase marked by a severe respiratory illness, often accompanied by multisystem dysfunction, coagulopathy, and shock is observed. This phase of the illness is characterized by hypercytokinemic inflammation and is often referred to as "cytokine storm." While the immunopathogenesis remains unclear, prospects of treating this severe phase of the illness with immunotherapy are evolving, with some treatments showing promise.