Exposure to Mild Hypoxia Associated with Oral Breathing Affects The NK Cell Ratio in The Spleen

抄録

　An upper respiratory tract obstruction due to nasopharyngeal diseases such as allergic rhinitis and tonsillar hypertrophy/sinusitis in growing children inhibits normal nasal breathing and leads to oral breathing. One symptom of this phenomenon appearing in the living body is hypoxia. Typically, it is rare for hypoxia associated with an upper respiratory obstruction to become severe and cause dyspnea, and it generally causes mild hypoxia. However, there are no previous reports regarding the effect of mild hypoxia on the living body. Thus, in this study, in order to examine the effect of mild hypoxia on the entire body, alterations in the immune system of growing rats using a mild hypoxia exposed model were evaluated.
　Six-week-old Wistar male rats were used(n=60)and assigned to either the mild hypoxia group(18% FIO₂)or control group. In both groups, five experimental time points, days 1, 3, 7, 14, and 21, were set. After the rats were sacrificed at each time point, the spleen was removed and the natural killer(NK)cell ratio(CD3^-/CD161⁺)in splenic lymphocytes were compared by flow cytometry.
　The NK cell ratio of the day 1 group within the mild hypoxia group was significantly higher compared to that of the control group(P<0.05). Moreover, the NK cell ratio of the mild hypoxia groups indicated were significantly lower than those of the control groups for day 7, 14, and 21(P<0.05).
　The exposure to mild hypoxia in growing rats may change the NK cell ratio in the splenic lymphocytes.