May 17, 2008 When killer T cells of the immune system encounter
virus-infected or cancer cells, they unload a lethal mix of
toxic proteins that trigger the target cells to self-destruct. A
new study shows T cells can initiate cellular suicide, also
known as programmed cell death or apoptosis, by a previously
unrecognized pathway that starts with the destruction of a key
enzyme in mitochondria, the power plant of the cell. The study,
from the lab of Judy Lieberman, a senior investigator at the
Immune Disease Institute and Professor of Pediatrics at Harvard
Medical School, reveals that T cells use both the novel pathway
and the classical apoptotic pathway to interfere with
mitochondrial function and induce cell death. "This work gives
us a new understanding of a major T cell defense pathway,"
Lieberman says. The Lieberman lab studies cytotoxic T
lymphocytes (CTLs), key cells in the immune defense against
viral infection and cancer. When CTLs recognize an infected or
transformed target cell, they release the con