RESUMEN
Natural killer (NK) cells play an important role in host defense.NKG2D is expressed as a homodimer on the surface of NK cells and is an important lymphocyte activating receptor.NKG2D ligands are negatively or poorly expressed on the surface of normal cells,but when the cells are in a state of oxidative stress,malignant transformation,autoimmune or inflammatory stimulation,these ligands will be induced on the cell surface.The NKG2D receptor and its ligand-mediated cellular immune response play an important role in immune surveillance of tumor cells,and at the same time it is also closely related to certain autoimmune diseases.
RESUMEN
T cells are divided into two subsets,αβΤandγδT cells, according to the T-cell recep-tor ( TCR) expressed. γδT cells are a small minority of T cells and in contrast to αβΤ cells, they do not seem to require antigen processing and major-histocompatibility-complex ( MHC ) presentation of peptide epitopes. This group of T cells is usually much less common than αβT cells, but plays an important role in anti-infection, anti-tumor and immunoregulation. This review summarizes the production, development, dis-tribution, genetic characteristics, antigen recognition characteristics, biological and immunological functions of γδT cells as well as their unique roles and mechanisms in bacterial infectious diseases.