PDCD1LG2 and neoplasm: Further obstacles are posed by immunosuppressive cell types such as tumour-associated macrophages (TAMs), T regulatory cells (Tregs), and myeloid-derived suppressor cells (MDCSs) [39,40]; these cells express high levels of immune inhibitory molecules, such as programmed death receptor ligands (PD-L1 and PD-L2), galectin-9, and the so-called herpes virus entry mediator (HVEM), and secrete large amounts of anti-inflammatory cytokines, including transforming growth factor-β (TGF-β and interleukin (IL)-10 [39,41,42,43,44,45,46,47].