Apoptosis of Th1-like cells in experimental tuberculosis (TB)

Th1 cell-induced anti-mycobacterial immunity is lost during a progressive M ycobacterium tuberculosis infection in a susceptible host. This study was d esigned to test the mechanism of the loss of antimycobacterial cell-mediate d immune response. We demonstrate that M. tuberculosis infection results in increased Fas expression and decreased Bcl-2 expression in CD4(+) T cells. When CD4(+) T cells are stimulated in vitro, they show increased apoptosis and decreased production of IL-2 and interferon-gamma (IFN-gamma) but not of IL-4. These changes may result in selective apoptosis of Th1-like cells, leading to the loss of cell-mediated immune response against M. tuberculos is.