Effect of Nasal Obstruction on the Immune System

Objectives: 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. Persistent nasal obstruction or oral breathing induces malocclusions, such as maxillary protrusion and/or an open bite. Previous studies have reported that nasal obstruction during growth changes the craniofacial morphology. However, there are no previous reports regarding the effect of nasal obstruction on the immune system of the living body. Thus, we examined the effect of nasal obstruction on the natural killer (NK) cell ratio (CD3-/CD161+) and the percutaneous arterial oxygen saturation（SpO2) in growing rats using a unilateral nasal obstruction model.
Methods: Six-week-old male Wistar rats (n=60) were used for this study and assigned to either the unilateral nasal obstruction group or the control group. In both groups, the SpO2 levels were measured by a pulse oximeter at five experimental time points, namely days 1, 3, 7, 14, and 21. Then the spleen was removed each rat in each group and the NK cell ratios among splenic lymphocytes were compared by flow cytometry.
Results: The body weights of the unilateral nasal obstruction group and control group were no significant differences at days 7, 14, 21. The SpO2 level of the unilateral nasal obstruction group significantly decreased compared to the control group at approximately 93%（P<0.05）. In addition, the NK cell ratio of the unilateral nasal obstruction group was significantly lower than the control group throughout the experimental period（P<0.05）.
Conclusions: The findings of the present study therefore suggest that unilateral nasal obstruction in growing rats reduces the SpO2 level and may also cause a decrease in the NK cell ratio in the spleen.