TGFB1 and neoplasm: Multiple immunosuppressive cell types, including tumor-associated macrophages (TAMs), MDSCs and tumor-associated neutrophils (TANs), actively inhibit antitumor immunity mediated by CD8+ T cells through direct contact or secretion of suppressive cytokines (e.g., IL-10 and TGF-β), reactive oxygen/nitrogen species and immune checkpoint ligands (Fig. 2C).