SURFACTANT PROTEIN-A IN BRONCHOALVEOLAR LAVAGE FLUID

We measured surfactant protein A and phosphatidylcholine in the bronchoalveolar lavage fluid from healthy volunteers and several groups of patients with lung diseases to obtain information on surfactant in the lung. We developed three types of enzyme-linked immunosorbent assays that used combinations of polyclonal antiserum and monoclonal antibodies. Phosphatidylcholine was assessed by enzymatic measurement. The median amounts of surfactant protein A in bronchoalveolar lavage fluid determined by the enzyme-linked immunosorbent assay with monoclonal antibodies were as follows: control subjects (n = 10), 2.82 mg/L (range, 0.92 to 5.17 mg/L); patients with asthma (n = 13), 1.89 mg/L (range, 0.45 to 2.95 mg/L); and patients with pulmonary sarcoidosis (n = 20), 2.98 mg/L (range, 0.68 to 7.02 mg/L). The median phosphatidylcholine concentrations in the bronchoalveolar lavage fluid were as follows: control subjects (n = 10), 20-mu-mol/L (range, 3 to 37-mu-mol/L); patients with asthma (n = 12), 24-mu-mol/L (range, 3 to 55-mu-mol/L); and patients with pulmonary sarcoidosis (n = 20), 26-mu-mol/L (range, 4 to 76-mu-mol/L). As a group, the patients with asthma had less surfactant protein A in bronchoalveolar lavage fluid than did the control subjects (Mann-Whitney U test, p < 0.05). The surfactant protein A levels measured by the enzyme-linked immunosorbent assay with polyclonal antiserum and by a competitive enzyme-linked immunosorbent assay were also lower in bronchoalveolar lavage fluid from patients with asthma than in that from control subjects. The phosphatidylcholine concentrations in all groups were similar. By using phosphatidylcholine to normalize surfactant protein A values we found that the ratios of surfactant protein A to phosphatidylcholine were lower in the patients with asthma than in the control subjects (Mann-Whitney U test, p = 0.008). We conclude that the enzyme-linked immunosorbent assays are useful for the analysis of surfactant protein A in bronchoalveolar lavage fluid and that we may be able to discriminate abnormal concentrations in certain lung diseases.