ALVEOLAR MACROPHAGE SUBPOPULATIONS IN PATIENTS WITH ACTIVE PULMONARY TUBERCULOSIS

Alveolar macrophages are a heterogeneous cell population. The heteroge neity of alveolar macrophages recovered by bronchoalveolar lavage (BAL ) from 12 patients with active pulmonary tuberculosis (TB) and 10 norm al subjects was studied using Percoll density fractionation. The numbe rs and subsets (on the basis of CD3, CD4, and CD8 monoclonal antibodie s) of lymphocytes in BAL were measured by flow cytometry. Alveolar mac rophages recovered from patients with TB were mainly in the lower-dens ity fractions (<1.030 and 1.030 to 1.040 g/ml), whereas alveolar macro phages from normal subjects were in the higher-density fractions (1.05 0 to 1.070 and >1.070 g/ml). There were no significant differences in alveolar macrophages repartition between smokers and nonsmokers in eit her patients with TB or normal subjects. The significant changes in th e proportions of the lowest fraction and the higher fractions of alveo lar macrophages in patients with TB were not altered after division of our patients into smoker and nonsmoker subgroups when compared with c orresponding subgroups in normal subjects. The proportion of the alveo lar macrophages in the lowest fraction was inversely related to the ba cterial load of sputum and the disease extent on chest radiography in TB patients. The CD4/CDS ratio was significantly higher in patients wi th TB. This study shows that alveolar macrophages from TB patients are heterogeneous with hypodense cells predominant probably by interactio n with T lymphocytes. Changes in the proportions of alveolar macrophag es within subpopulations may be of critical importance in determining the overall response of the lung to TB infection.