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.