Tubercle bacilli and the defence factors for infection in sputum and bronchoalveolar lavage fluid

The defence factors against infection in sputum and bronchoalveolar lavage fluid (BALF) of patients with pulmonary tuberculosis were measured. As the defence factors, lactoferrin, lysozyme and secretory IgA (sIgA) in sputum or BALF of patients with bacilli (+) or (-) tuberculosis were measured and compared. Lactoferrin in sputum was significantly higher in patients with sputum smear positive tuberculosis compared with patients with smear and culture negative tuberculosis. SIgA in sputum was significantly higher in smear negative and culture positive cases compared with culture negative cases. As to the lysozyme in sputum, significant difference was not proved between each group. The level of these factors in BALF did not show significant difference between bacilli (+) and (-) cases. Neither significant correlation was observed among the level of three defence factors in sputum or BALF, nor between the number of leucocyte and tubercle bacilli in sputum. In tubercle bacilli positive group, however, significant positive correlation between the number of leucocyte and lactoferrin in sputum was found. In vitro experiments, high concentration of lactoferrin or lysozyme inhibited the growth of standard strain of tubercle bacilli (H37Rv) and BCG. The results suggest that the measurement of lactoferrin, lysozyme and sIgA in sputum or BALF is useful to determine the clinical activity of tuberculosis.