TGFB1 and neoplasm: Although dNKs, tissue resident NK cells and ILC1s were originally believed to be developmentally distinct from cytotoxic NK cells in the circulation, recent studies have identified significant plasticity in circulating NK cells, whereby they can adopt an ILC1-like phenotype in response to trophoblast or tumor-derived factors, such as transforming growth factor-β (TGF-β) (3, 7–9).