Additionally, MDSCs can secrete immunosuppressive cytokines, such as TGF-β and IL-10, to induce regulatory T-cell development, which has been implicated in the regulation of various immune processes in diseases, including infection.12 The numbers of T cells and NK cells were reduced in SARS-CoV-2-infected patients, which was probably due to the combinational interactions of these cells. This evidence concerns the gene TGFB1 and infection.