Anti-neoplastic and immunostimulatory effects of low-dose X-ray fractions in mice.
OBJECTIVE
The exploration of immune mechanisms of the tumour-inhibitory effect of exposures to low-level fractions of X-rays.


METHODS
BALB/c mice were exposed to whole-body daily irradiations with 0.01, 0.02, or 0.1 Gy X-rays per day for 5 days/week for two weeks. Then, mice were intravenously injected with L1 tumour cells, killed 14 days later, and neoplastic colonies were counted in the lungs. Natural killer (NK) cell-enriched splenocytes and activated peritoneal macrophages (Mϕ) were collected and cytotoxic activities of these cells against susceptible tumour targets were assayed. Concanamycin A (CMA) and antibody against the ligand for the Fas receptor (FasL) were used to inhibit the NK cell-mediated cytotoxicity. Production of nitric oxide (NO) was quantified using the Griess reagent. Secretion of interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-12 (IL-12), and tumour necrosis factor-α (TNF-α) was measured using the enzyme-linked immunosorbent assays.


RESULTS
All the exposures to X-rays significantly reduced the number of the induced tumour colonies and enhanced cytotoxic properties of the NK cell-enriched splenocytes and activated Mϕ.


CONCLUSIONS
Suppression of the growth of pulmonary tumour colonies by irradiations of mice with low-dose fractions of X-rays may result from stimulation of anti-tumour reactions mediated by NK cells and/or cytotoxic macrophages.
Department of Radiobiology & Radiation Protection, Military Institute of Hygiene & Epidemiology, Warsaw, Poland.
Ewa M
EM
Nowosielska
Aneta
A
Cheda
Jolanta
J
Wrembel-Wargocka
Marek K
MK
Janiak
D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000276:immunology / Q000378:metabolism / Q000528:radiation effects*; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D019583:Dose Fractionation, Radiation; D007114:Immunization / Q000379:methods*; D007694:Killer Cells, Natural / Q000276:immunology / Q000378:metabolism / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D008262:Macrophage Activation / Q000528:radiation effects; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism / Q000528:radiation effects*; D013997:Time Factors; D014916:Whole-Body Irradiation / Q000379:methods; D014965:X-Rays
D016207:Cytokines