The concentrations of IgA and free secretory piece in the nasal secretions of patients with recurrent respiratory infections.

The concentrations of total IgA, 11S IgA, total and free secretory piece (SP) were measured in the nasal secretions of 39 patients with recurrent upper and lower respiratory tract infections during an infection free period. In all of eight patients who had selective serum IgA deficiency (less than 0.05 g/l) IgA was also undetectable in their nasal secretions and the mean concentration of free SP was significantly raised. However, the mean concentrations of 11S IgA, SP and free SP in nasal secretions of patients with normal or low (greater than 0.05 g/l but below the normal range) serum IgA were not significantly different from those of 10 healthy normal subjects. In patients with detectable nasal secretory IgA, 11S IgA concentrations correlated significantly (r = 0.57; P less than 0.001) with concentrations of free SP. One patient with normal serum IgA was found to have a large excess of free SP and therefore may have had a relative defect in local IgA production.