Human leukocyte antigen-G (HLA-G) is a non-classical HLA class Ib molecule of low polymorphism whose expression is restricted to immunoprivileged sites, such as placenta.Four membrane-bound (HLA-G1-G4) and three soluble HLA-G isoforms (HLA-G5-G7) are interact with inhibitory receptors such as Ig-like transcript-2 (ILT-2) and Ig-like transcript-4 (ILT-4).These receptors are mainly expressed on natural killer (NK) cells, CD4+T cells, CD8+T cells so HLA-G negatively affects almost every aspect of immunity, inhibiting allogeneic T-cell and NK cell cytotoxicity as well as T cell proliferative response.Tumor cells, frequently associated with total or partial loss of HLA class-Ⅰ expression and escape from both CD8+ T cells and NK cells cytoxicity.