Effects of Nasal Instillation of Staphylococcal Enterotoxin B on Nasal and Bronchial Mucosa in BALB/c Mouse

ABSTRACT

BACKGROUND AND OBJECTIVES: The effect of nasal exposure to staphylococcal enterotoxin in the pathogenesis of allergic rhinitis remains controversial. We sought to determine the effect of increasing doses of intranasally applied Staphylococcus aureus enterotoxin B (SEB) on the respiratory mucosa, especially the nasal mucosa. MATERIALS AND METHODS: Nasal application of SEB was performed on four occasions (days 0-4-8-12) in unsensitized BALB/c mice. Control mice were intranasally treated with phosphate buffered saline (PBS), and 5 ng, 50 ng, 500 ng, and 5 microg of SEB was applied to the respective experimental group. The concentrations of IL-4, IL-5, and IFN-gamma in bronchoalveolar lavage fluid (BALF), nasal lavage fluid (NLF) and serum were compared among groups. Also, the counts of total inflammatory cells, macrophages, lymphocytes, neutrophils, eosinophils, and basophils in BALF and NLF were compared among the groups. Pathologic studies for inflammatory cell infiltration in the nasal mucosa and peribronchial area were conducted. RESULTS: IL-4 and IFN-gamma showed higher concentrations with increasing stimulation dose of SEB in NLF and serum. The IL-5 concentration showed a tendency to increase in NLF and serum, but these changes were not statistically significant. Total inflammatory cell count, especially macrophage count, in BALF and NLF was higher with increasing stimulation dose of SEB. Infiltration of inflammatory cells into the nasal mucosa showed a tendency to increase in a dose-dependent manner. CONCLUSION: These results suggest that nasal exposure to SEB may induce Th1 and Th2 inflammatory responses in the respiratory mucosa, especially the nasal mucosa.