CSF2 and COVID-19: Immunosuppression has thus been proposed as a means to resolve cytokine storms in severe COVID-19 cases, and clinical trials employing immunosuppressive drugs (methylprednisolone, hydroxychloroquine, chloroquine, and leflunomide); inhibitors of pro-inflammatory cytokines (IFN-γ, IL-1β, IL-6, IL-17A, M-CSF, and TNF-α); and modulators of factors that regulate innate and adaptive immune reactions (C5, CD47, GM-CSF, M-CSF, and sphingosine-1-phosphate) in COVID-19 patients are currently underway 7, 11.