Serum IgA and secretory IgA levels in bronchial lavages from patients with a variety of respiratory diseases.

The secretory immunoglobulin A (IgA) system plays an important role in the protection of epithelial surfaces. The aim of this study was to evaluate whether the measurement of the primary airway Ig (sIgA) concentration in bronchial washings is clinically useful in patients with airway epithelial injury or inflammation. We measured serum IgA levels and sIgA concentrations in the bronchial lavages of patients with chronic bronchitis (n = 10), bronchiectasis (n = 15), lung cancer (n = 15) and in healthy control subjects (n = 10). Absolute sIgA levels of bronchial lavage fluids in the chronic bronchitis, bronchiectasis and lung cancer groups were higher than the controls, but there was no significant difference between the groups. sIgA/ml recovered bronchial fluid ratios were similar in the all groups. Standardisation of samples by means of albumin concentration ratios (sIgA/alb) showed that the bronchial lavages of the patients with lung cancer, chronic bronchitis and bronchiectasis were generally similar and demonstrated a significantly decreased sIgA/alb ratio compared to that of control subjects (p = 0.001, p < 0.05 and p < 0.05). sIgA/alb ratios in bronchial lavages recovered from involved lung of the patients with lung cancer and bronchiectasis were lower as compared to uninvolved lung (p < 0.001 and p < 0.05). There was no significant difference in serum IgA levels between all groups. As a result, although our findings seem partly to confirm the hypothesis that local bronchial IgA secretion is impaired in areas of bronchial epithelial injury or inflammation, we thought that sIgA would be useless as a marker of respiratory epithelial injury or inflammation in patients with chronic bronchitis, bronchiectasis and lung cancer.