Specific immune response against pseudomonas aeruginosa and haemophilus influenzae in severe COPD

Introduction The bronchial mucosa is protected by a specialized immune system focused on the prevention of colonization and infection by potentially pathogenic microorganisms (PPMs), being IgA the principal immunoglobulin and a key element in this mechanism. Changes in the structure and function of the airway epithelium may lead to a defective immune barrier in COPD that would facilitate the recurrent presence of PPMs Objective To determine the bronchial specific immune response against Pseudomonas aeruginosa (PA) and Haemophilus influenzae (HI) in patients with stable severe COPD Methods Levels of IgA antibodies specific for PA and HI were determined by ELISA in sputum supernatant samples of 36 stable COPD patients, 15 of them showing chronic colonization by PA, using as reference 10 healthy controls Results Included subjects had a mean age of 70.5 (SD 7) years and a severe impairment in their lung function (FEV 1 35 [SD 13] % of predicted). The levels of specific IgA against PA, expressed as a ratio from values in healthy controls, were below one in most patients and higher in colonized than in non-colonized patients [median= 0.56 (IQR -0.40 – 1.78) vs -0.85 (-0.95 – -0.64), p Conclusions In severe COPD patients the IgA-based immune response against PA and HI was lower than the healthy controls, confirming a defective local immune response to specific respiratory pathogens in these patients. Levels of IgA specific against PA were higher in PA-colonized patients, but did not reach reference values in most of them.