IL4 and COVID-19: Consistent with previous studies, we observed a dramatic increase of IL-6, IL-1β, IL-8, and TNF-α in BALF in adult COVID-19 patients, which is the main hyperinflammatory feature of severe COVID-19 patients while both IL-4 and IL-10 moderately increased to act as anti-inflammatory cytokines through a negative feedback mechanism (Xiong et al., 2020).