In this study, we have investigated if current cancer therapeutic modalities including hyperthermia and ionizing radiation can increase the expression of NKG2D ligands in human cancer cell lines. The expressions of NKG2D ligands were induced by both heat shock and ionizing radiation in various cell lines including KM12, NCI-H23, HeLa and A375 cells with peaks at 2 h and 9 h after treatment, respectively, although inducibility of each NKG2D ligand was various depending on cell lines. During the induction of NKG2D ligands, heat shock protein 70 was induced by heat shock but not by ionizing radiation. These results were followed by increased susceptibilities to NK cell-mediated cytolysis after treatment with heat shock and ionizing radiation. These results suggest that heat shock and ionizing radiation induce NKG2D ligands and consequently might lead to increased NK cell-mediated cytotoxicity in various cancer cells.
Tumor Cells, Cultured ; Receptors, Immunologic/*metabolism ; Radiation, Ionizing ; Neoplasms/immunology/*radiotherapy/therapy ; *Ligands ; Killer Cells, Natural/*immunology ; Hyperthermia, Induced/methods ; Humans ; Hela Cells ; *Heat-Shock Response/physiology ; Heat ; HSP70 Heat-Shock Proteins/metabolism/radiation effects ; Gene Expression Regulation, Neoplastic/radiation effects ; Cytotoxicity, Immunologic/*physiology/*radiation effects ; Antigens, Surface/metabolism/radiation effects

Constructing a bone marrow chimera prior to graft transplantation can induce donor-specific immune tolerance. Mixed chimerism containing hematopoietic cells of both recipient- and donor-origin has advantages attributed from low dose of total body irradiation. In this study, we explored the mechanism of mixed chimerism supplemented with depletion of Natural Killer cells. Mixed chimerism with C57BL/6 bone marrow cells was induced in recipient BALB/c mice which were given 450 cGy of gamma-ray irradiation (n = 16). As revealed by reduced proliferation and cytokine production in mixed leukocyte reaction and ELISpot assay (24.6 vs 265.5), the allo-immune response to bone marrow donor was reduced. Furthermore, the induction of transferable immunological tolerance was confirmed by adoptive transfer and subsequent acceptance of C57BL/6 skin graft (n = 4). CD4+FoxP3+ regulatory T cells were increased in the recipient compartment of the mixed chimera (19.2% --> 33.8%). This suggests that regulatory T cells may be therapeutically used for the induction of graft-specific tolerance by mixed chimerism.
Animals ; Bone Marrow Cells/cytology ; *Bone Marrow Transplantation ; Cell Proliferation ; Chimerism ; Cytokines/metabolism ; Gamma Rays ; Graft Survival ; *Immune Tolerance ; Killer Cells, Natural/immunology/radiation effects ; Leukocytes/immunology/radiation effects ; Mice ; Mice, Inbred BALB C ; Mice, Inbred C57BL ; Models, Animal ; Skin Transplantation ; T-Lymphocytes, Regulatory/cytology/*immunology/metabolism ; Whole-Body Irradiation