It is hypothesized that the beneficial effect of MSC treatment for patients with severe COVID-19 is mediated via reduction of pro-inflammatory cytokines, that jointly mediate immune pathology and worsen clinical COVID-19 outcomes.7,27–29 Cytokines such as serum IL-6 are considered as biologically relevant biomarkers associated with disease progression of COVID-19. This evidence concerns the gene IL6 and COVID-19.