PDCD1 and neoplasm: TGF-β is expressed by tumor cells, stromal cells, and immunosuppressive cells that can attenuate CD8+ T cell function,208,209 inhibit CD8+ T cell infiltration,210 expand Tregs,211 and polarize neutrophils into pro-tumor populations.212 The value of simultaneous blockade of PD-1/PD-L1 axis and TGF-β is underscored by the development of bintrafusp alfa, which is a fusion antibody composed of an anti-PD-L1 antibody fused to the extracellular domain of human TGF-β receptor II (Figure 2g).