Analysis of IgA antibody to Pseudomonas aeruginosa in sera and sputa of patients with chronic airway diseases.

The change of IgA system for Pseudomonas infection was examined by enzyme-linked immunosorbent assay of the system in sera and sputa of patients with chronic airway diseases. The anti-Pseudomonas total IgA antibody titers in both sera and sputa were not elevated in group I with no infection (mainly chronic bronchitis) and group II infected with bacteria other than Pseudomonas, but were elevated in group III colonized transiently with Pseudomonas [diffuse panbronchiolitis (DPB) and bronchiectasis] and group IV colonized persistently with Pseudomonas (mainly DPB). The elevation in the sera and sputa were mainly due to monomeric IgA and polymeric IgA (S-IgA), respectively, and values were significantly higher in group III than in group IV only in the sera. These results indicate that the IgA system is enhanced in advanced DPB and bronchiectasis complicated by Pseudomonas infection, and that the anti-Pseudomonas IgA antibody titer in serum is more useful than that in sputum for the diagnosis of respiratory Pseudomonas infection.