15 Cell Death

Abstract

I. INTRODUCTION
Programmed cell death is a common cell fate in most if not all multicellular animals. Cell death is used extensively during development, as well as later in life, to eliminate cells that are either useless or potentially detrimental to the organism. Programmed cell death is basically cell suicide, in the sense that the cell which is to die actively participates in — and often itself induces — its own demise and removal from the organism. Proper control of programmed cell death is crucial, and breakdown in the regulation of this process can result in a number of pathologies: Inactivation of the death program has been associated with the development of cancer and autoimmune diseases, whereas aberrant activation of the apoptotic machinery is thought to contribute to the extensive cell deaths observed in neurodegenerative diseases and stroke (Vaux 1993; Thompson 1995).

Programmed cell death is often also called apoptosis, particularly in vertebrates. The term apoptosis was introduced by Kerr et al. (1972) to emphasize that programmed cell deaths are morphologically very different from necrotic deaths. Because the original definition of apoptosis was based on strict morphological criteria, there has been considerable debate as to whether all programmed cell deaths in mammals were of the apoptotic type. It is now generally agreed that most, if not all, programmed cell deaths in mammals occur by apoptosis.

As its name implies, programmed cell death is thought to be mediated by a specific molecular program activated by the cell if and when it needs to...