RESUMO
The effect of low-intensity laser light on the activity of natural killer cells from healthy and tumor-bearing mice was studied. Skin in the zone of the thymus or hind limb was illuminated, the remaining body surface being screened. The illumination was carried out for 30 days, with the duration of a single exposure being 1 min and intervals between the exposures being 48 h. The effect of laser light depended on the location of the illuminated area. It was shown that the exposure of the thymus of healthy animals for 20 and 30 days leads to a significant decrease in the activity of natural killer cells. On the contrary, the illumination of the limb for 10 or 20 days increased the activity of natural killer cells; but when hind limbs were treated for 30 days, the activity of natural killer cells decreased. Whereas tumor growth increased the natural killer cell activity, the illumination of tumor-bearing mice lowered the adaptive antitumoral resistance by decreasing the activity of natural killer cells.
