Profile of airway mucins in bronchoalveolar lavage fluid of patients with pulmonary alveolar proteinosis

Abstract

Background: Pulmonary alveolar proteinosis (PAP) occurs in association with impairment of macrophages, which leads to alveolar surfactant accumulation and opportunistic infections. Recently, MUC5B, one of the major mucins in airways is reported to be required for airway defense; MUC5B deficiency caused dysfunction of macrophages, resulting chronic infections. However, mucin composition of airway mucus in patients with PAP is unknown. Aims: To determine whether abnormality of mucin composition is present in patients with PAP, we measured major secreted airway mucins, MUC5AC and MUC5B in bronchoalveolar lavage fluids (BALF) of the patients with PAP. Methods: Diagnostic BAL was performed via fiberoptic bronchoscopy according to established guidelines. After BAL, patients who met criteria for PAP and patients who showed no apparent lung disease were enrolled to the study. The MUC5AC and MUC5B protein levels in BALF were measured by enzyme-linked immunosorbent assay. Results: The mean percentage of lymphocytes in BALF was significantly higher in patients with PAP. The MUC5AC levels were similar in both groups, whereas the MUC5B levels were significantly lower in patients with PAP compared with control (Fig. 1). Conclusions: MUC5B production in airways is decreased in patients with PAP. Alteration of mucin composition may lead to the dysfunction of macrophages, resulting opportunistic infections in patients with PAP.