Effects of X-ray irradiation on natural killer (NK) cell system. II. Increased sensitivity to natural killer cytotoxic factor (NKCF).
Irradiation with low-doses of X-rays of tumor cells elevated their susceptibility to lysis by natural killer (NK) cells in an accompanying paper. Cytotoxicity assays conducted at the single cell level revealed that X-ray irradiation of K562 cells did not affect the number of effector-target conjugates but increased the frequency of dead conjugated target cells. During interaction with K562 cells large granular lymphocytes released a soluble cytotoxic factor (NKCF) that killed the target cells. X-ray irradiation did not affect the NKCF stimulatory ability of K562 cells, while it elevated their sensitivity to the lytic effect of NKCF. In contrast to X-rays, exposure to ultraviolet (UV) radiation of K562 cells did not elevate their NK sensitivity but rather reduced it. Treatment with mitomycin C produced no effect on NK sensitivity. These results indicate that X-ray irradiation elevates the target sensitivity to NKCF, which may be involved in the increased NK sensitivity, and that the X-ray effect may be different from that of UV radiation or DNA synthesis inhibition.
Uchida
A
A
Radiation Biology Center, Kyoto University, Japan.
Mizutani
Y
Y
Nagamuta
M
M
Ikenaga
M
M
D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic / Q000528:radiation effects; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology / Q000528:radiation effects*; D007951:Leukemia, Myeloid / Q000276:immunology; D008937:Mitomycins / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
D008937:Mitomycins