Effect of in vitro infection of human monocytes with low numbers of Mycobacterium tuberculosis bacteria on monocyte apoptosis. Infect Immun

The effect of Mycobacterium tuberculosis H37Rv on spontaneous apoptosis of human monocytes from healthy donors in vitro was investigated. Infection with low numbers of viable M. tuberculosis bacteria prevented spontaneously occurring apoptosis in monocytes. Our data suggest that apoptosis of monocytes appears to be negatively associated with the presence of tumor necrosis factor alpha. As inflammation wanes, the number of monocytes and mac-rophages in the lesion decreases, suggesting the existence of a physiologic mechanism for eliminating these cells when they are no longer necessary. Apoptosis seems to be a physiological mechanism for removing cells from the body without inducing inflammation and subsequent damage of contiguous cells (4, 11). Apoptosis occurs through the activation of a cell-intrinsic suicide program. The basic machinery to carry out apoptosis appears to be present in essentially all mammalian cells at all times, but the activation of the suicide program is regulated by many different signals that originate from both the intracellula