Specific IgA against in severe COPD.

Background: The bronchial mucosa is protected by a specialized immune system focused on the prevention of colonization and infection by potentially pathogenic microorganisms (PPMs). Immunoglobulin A (IgA) is the principal antibody involved in this mechanism. A defective immune barrier may facilitate the recurrent presence of PPMs in COPD.

Purpose: The aim of this study was to determine IgA-mediated bronchial specific immune responses against in stable patients with severe disease.

Methods: COPD patients with good-quality sputum samples obtained during stability were included and classified according to the presence or absence of chronic bronchial colonization by . Levels of specific IgA for in sputum were determined by ELISA and expressed as ratios, using the pooled level of 10 healthy subjects as reference (optical density patient/control).

Results: Thirty-six stable COPD patients were included, 15 of whom had chronic colonization by . Levels of specific IgA against in stable non-colonized patients were lower than those in healthy subjects (IgA ratio: median =0.15 [interquartile range {IQR} 0.05-0.36]). Colonized patients had higher levels, (1.56 [IQR 0.59-2.79]) (<0.001, Mann-Whitney test), with figures equivalent but not exceeding the reference value.

Conclusion: IgA-based immune response against was low in severe COPD patients. Levels of specific IgA against this microorganism were higher in colonized patients, but did not attain clear-cut levels above the reference. An impaired local response against may favor chronic colonization and recurrent infections in severe COPD.