TGFB1 and COVID-19: Elevated serum levels of TGF-β correlated with lung fibrosis in a cohort of severe COVID-19 patients (108).This study also reported increased serum levels of TGF-β and of MDSC in COVID-19 patients, as well as a significant correlation between COVID-19 severity and serum TGF-β levels; and showed that isolated M-MDSC from these patients produced higher levels of intracellular TGF-β than non-M-MDSC (108).