IL6 and COVID-19: Moreover, a recent study performed by Zheng et al. demonstrated in vitro differentiated mDC and macrophages to produce IFN-α, TNF-α, and IL-6 upon SARS-CoV-2 infection (35).In correlation with this, high levels of IL-6 in critically ill COVID-19 patients are assumed to be produced by highly inflammatory macrophages (40).