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Harumi Jyonouchi, MD; Sining Sun, DDS; Cynthia A. Kennedy, MD; Frank L. Rimell, MD

Arch Otolaryngol Head Neck Surg. 2000;126:529-532.

Background  Previously, we found minimal bacterial dissemination and no evidence of systemic inflammation in a rabbit sinusitis model in which the left maxillary sinus was inflamed by Bacteroides inoculation with the ostium closed. However, we observed an increase in anti-Bacteroides IgG antibodies in the contralateral sinus, lower airway, and middle ear, with an apparent increase in interferon gamma (IFN-) messenger RNA expression in the ear and sinus mucosa.

Objective  To evaluate how IFN- production in the upper and lower airway is associated with localized bacterial sinusitis.

Design  Interferon gamma levels were measured in lavage solutions from the sinus, airway, and middle ear and in serum at 1, 2, 3, and 4 weeks following bacterial inoculation.

Subjects  The subjects were 6 rabbits at each time point. The controls were untreated (n=5) and sham-operated (n=4-5) rabbits at 2 and 4 weeks.

Intervention  Bacteroides fragilis (10⁸ plaque-forming units) was inoculated into the left maxillary sinus.

Results  Interferon gamma levels in the ear and sinus were less than 0.2 µg/g protein in controls. Following bacterial inoculation into the left sinus, IFN- levels increased up to 10-fold in both sinuses and even more in the middle ear at 3 weeks, independent of bacterial dissemination. Mean ± SD IFN- levels in the airway (0.3 ± 0.28 µg/g protein in controls) were not altered by bacterial inoculation into the sinus. Serum IFN- levels were very low (<0.05 µg/g protein) in most rabbits and were unchanged by bacterial inoculation.

Conclusions  Interferon gamma levels increase in the ear and contralateral sinus in response to localized sinus inflammation, indicating concerted mucosal proinflammatory immune responses in the upper airway. Such responses may lead to the aseptic middle ear inflammation often observed in patients with chronic sinusitis.

From the Departments of Pediatrics (Drs Jyonouchi and Sun) and Otolaryngology (Drs Kennedy and Rimell), School of Medicine, University of Minnesota, Minneapolis.