BAL neopterin - A novel marker for cell-mediated immunity in patients with pulmonary tuberculosis and lung cancer

Background: Neopterin is derived from guanosine triphosphate and is produced by stimulated macrophages under the influence of gamma -interferon of lymphocyte origin. It has been suggested that it is an excellent marker for the activation of the monocyte/macrophage axis in some clinical situations. However, to our knowledge, the relationship of BAL neopterin levels to disease states has not been studied. Aim: To assess the usefulness of BAL neopterin levels as an index of disease activity in patients with pulmonary tuberculosis and lung cancer. Methods:: BAL and serum neopterin levels were evaluated in 20 patients with pulmonary tuberculosis, 20 patients with bronchogenic carcinoma, and 10 healthy individuals. The concentration of neopterin was evaluated by radioimmunoassay technique. The BAL level of neopterin was standardized using the BAL urea level. Results: The neopterin levels (mean +/- SD) in the BAL and serum of tuberculous patients (88.6 +/- 27.4 nmol/L epithelial lining fluid [ELF], 61.3 +/- 29.4 nmol/L, respectively) were significantly higher when compared with those in lung cancer patients (40.7 +/- 16.6 nmol/L ELF, 26.8 +/- 6.58 nmol/L, respectively, p < 0.001) and when compared with those in control subjects (26.3 +/- 11.3 nmol/L ELF, 6.8 +/- 2.7 nmoVL, respectively, p < 0.001). In the tuberculous group, BAL and serum neopterin levels in patients with far-advanced disease were significantly higher when compared with those in patients with moderately and minimally advanced diseases (p < 0.001). BAL and serum neopterin levels were significantly higher in patients with small cell carcinoma than in those with adenocarcinoma (p < 0.05). BAL neopterin levels were significantly (p < 0.001) higher than serum levels in all patients and control groups. In addition, there were significant positive correlations between BAL and serum neopterin levels in tuberculous (r = 0.92, p < 0.001), lung cancer (r = 0.62, p < 0.001), and control groups (r = 0.93, p < 0.001). Conclusions: The levels of neopterin in BAL fluid may reflect the degree of disease activity in pulmonary tuberculous patients. In addition, BAL neopterin levels are elevated in patients with lung cancer, especially the small-cell carcinoma type.