TGFB1 and COVID-19: Mechanistically, the inhibition of T lymphocyte function by G-MDSCs obtained from COVID-19 patients has been shown to be dependent upon iNOS and TGF-β, as the treatment with a neutralizing antibody against TGF-β or with the NOS2 inhibitor, L-NG-nitro arginine methyl ester (L-NAME), reestablished the production of IFN-γ by T lymphocytes ex vivo [43].