Phenotypes of lung mononuclear phagocytes in HIV seronegative tuberculosis patients: evidence for new recruitment and cell activation

Mycobacterium tuberculosis preferentially resides in mononuclear phagocytes. The mechanisms by which mononuclear phagocytes keep M. tuberculosis in check or by which the microbe evades control to cause disease remain poorly understood. As an initial effort to delineate these mechanisms, we examined by immunostaining the phenotype of mononuclear phagocytes obtained from lungs of patients with active tuberculosis. From August 1994 to March 1995, consecutive patients who had an abnormal chest X-ray, no demostrable acid-fast bacilli in sputum specimens and required a diagnostic bronchoalveolar lavage (BAL) were enrolled. Of the 39 patients enrolled, 21 had microbiologically diagnosed tuberculosis. Thirteen of the 21 tuberculosis patients were either HIV seronegative (n = 12) or had no risk factor for HIV and constituted the tuberculosis group. For comparison, M. tuberculosis negative patients who had BAL samples taken during this time (n = 9) or normal healthy volunteers (n = 3) served as control group. Compared to the control group, the tuberculosis group had significantly higher proportion of cells expressing markers of young monocytes (UCHM1) and RFD7, a marker for phagocytic cells, and increased expression of HLA-DR, a marker of cell activation. In addition, tuberculosis group had significantly higher proportion of cells expressing dendritic cell marker (RFD1) and epithelioid cell marker (RFD9). These data suggest that despite recruitment of monocytes probably from the peripheral blood and local cell activation, host defense of the resident lung cells is insufficient to control M. tuberculosis

BRONCHOALVEOLAR LAVAGE CYTOLOGY AND IMMUNOCYTOLOGY IN PULMONARY TUBERCULOSIS

Limited data on the cellular and immunocytologic characteristics of bronchoalveolar lavage (BAL) fluid in pulmonary tuberculosis have been reported. We therefore studied 40 patients with active disease. BAL fluid differential cell counts and lymphocyte subsets were determined. The findings were compared with data from 47 patients with active sarcoidosis and 30 healthy control subjects. The proportion of lymphocytes was increased in both diseases (p < 0.001 versus control subjects) but with no difference compared to one another. The CD4/CD8 ratio was normal in 33 of 40 patients with pulmonary tuberculosis in contrast to sarcoidosis, with an increased ratio in 33 of 47 patients. HLA-DR(+) T lymphocytes were significantly increased in both pulmonary tuberculosis and sarcoidosis (p < 0.05 versus control group). The proportion of CD57(+) lymphocytes was normal in all study groups. We conclude that pulmonary tuberculosis and sarcoidosis are characterized by an increased percentage of lymphocytes in BAL fluid with a similar proportion of activated T cells. In contrast to active sarcoidosis, in which an elevated CD4/CD8 ratio is characteristic, in the majority of pulmonary tuberculosis patients the CD4/CD8 ratio is within the normal range