Function of the secretory immune system in bronchogenic carcinoma. Immunoglobulin A levels in respiratory secretions.

This study was designed to investigate the association between bronchogenic carcinoma of the lung and elevated immunoglobulin A (IgA) levels in respiratory secretions. Sixty-nine patients underwent bronchoscopic examination for evaluation of benign and malignant pulmonary diseases. The concentration of IgA in bronchoscopic washings was determined by a radioimmunoassay (RIA) procedure. The average IgA concentration in 20 washings from patients with benign disease was 171 micrograms/ml and agreed with reported IgA values in normal human volunteers undergoing bronchoscopic examination. In contrast, the average IgA concentration from patients with non--oat cell bronchogenic carcinoma was greater than 1,000 micrograms/ml, and 80% of these patients had values exceeding 300 micrograms/ml. Furthermore, in 16 of these patients, selectively collected washings had been obtained from the tumor-bearing lung and contralateral normal lung. In this group, elevated levels localized to the tumor-bearing side. In contrast, eight patients with extrathoracic cancer metastatic to the chest had an average IgA value of 160 micrograms/ml, and seven of eight (87%) had concentrations below 300 micrograms/ml. Aside from the association of cigarette smoking and pulmonary cancer, we found no clear relationship between smoking history and the concentration of IgA measured in secretions. Finally, biochemical analysis established that the changes in immunoglobulin levels were specific to the secretory immune system. In conclusion, measurement of secretory immune system components may be useful in the early diagnosis of malignant bronchogenic disease. Biological mechanisms and suggested clinical application are discussed.