When normal cells die, it is almost always by the process of apoptosis, whi
ch is a morphologic description. Some cells die readily and are rapidly rep
laced; others live as long as we do. Because apoptotic morphology is simila
r from cell to cell, researchers have embarked on an intense search for a c
ommon underlying biochemical process. There is an apoptotic mechanism or ce
ll death program, which is expressed in embryos and throughout life. Most t
issues, and especially the skin, gut, and immune system, depend on well-ord
ered apoptosis and cell replacement. Apoptosis can fail to occur, as in the
newly described autoimmune lymphoproliferative syndrome, or be turned on p
athologically, as in degenerative diseases, We would like to induce apoptos
is in dangerous cells or block it to preserve valuable cells. We need to kn
ow more about how apoptosis is regulated and what we can do to influence th
e process.