Secretory IgA(S-IgA) levels in sera from patients with diffuse panbronchiolitis.

The serum S-IgA levels of 33 patients with diffuse panbronchiolitis (DPB) were compared with those of 13 patients with chronic bronchitis (CB) and 24 patients with bronchiectasis (BE), to obtain information on differences in the pathologic states in DPB and other chronic bronchial diseases. The S-IgA levelw as elevated in all three bronchial diseases, being significantly higher in DPB than in CB, and intermediate in BE. Persistent bacterial infections developed in most of the patients with DPB and two-thirds of those with BE, but in few of those with CB. Serum S-IgA levels were especially high in patients expectorating Pseudomonas aeruginosa-positive sputum, who constituted two-thirds of the patients with DPB and about one-third of those with BE. The highest levels over (100 micrograms/ml) were observed in far-advanced patients with DPB who expectorated P. aeruginosa-positive sputum. The increase in the serum level of IgA was less than that of S-IgA in all three diseases. These results indicate that the marked elevation of the serum S-IgA level in patients with DPB is due to extensive, chronic infection of the airways of the lungs, especially the peripheral airways, and that serum S-IgA is a useful marker for determining the clinical stage and the pathologic state of patients with diffuse peripheral airway diseases.