The cause of paranasal sinusitis is still unknown although several factors have been implicated: underdevelopment of the paranasal sinuses, intranasal deformities, dysfunction of the mucosal defense mechanisms and allergy. Among them, the local immune system, including secretory IgA (SIgA), plays an important role in the defense mechanism of the upper respiratory tract. However, there have been no reports relating the concentration of SIgA in nasal secretions with the development of paranasal sinus infection.
We examined the concentration of SIgA in the nasal secretions of 48 patients with paranasal sinusitis, aged 3 to 15 years. Nasal secretion was obtained by the filter-paper method and diluted in 1cc of saline. The value of SIgA in these solutions was determined by enzyme-immunoassay and expressed as μg (SIgA)/g(nasal secretion). Furthermore, 12 patients were treated conservatively and the SIgA was determined periodically. The control group included 41 normal subjects aged 3 to 15 years.
The value of SIgA in nasal secretions was significantly lower in patients (569.0±291.0μig/g) with paranasal sinusitis than in the normal controls (847.7±387.6μg/g). The concentration of SIgA decreased significantly during treatment for paranasal sinusitis. These data suggest that the concentration of SIgA in nasal secretions might be lower congenitally in patients with paranasal sinusitis and that it was elevated after the onset of bacterial infection of the nose and paranasal sinuses.