Apoptosis plays an important role in development, homeostasis, and dis
ease. Current work has suggested that apoptosis can be evoked by multi
ple stimuli that, in turn, initiate distinct death pathways. Recently,
exciting advances have been made in the understanding of biochemical
pathways that regulate apoptotic processes. These pathways contain bot
h evolutionarily conserved elements and components that are dependent
on the death stimulus and cell context. Accordingly, this review focus
es on the compositions and relative ordering of the apoptotic pathways
in four different death paradigms: activation of receptor of the Fas
ligand, destruction by cytotoxic T lymphocytes, exposure to DNA damagi
ng agents, and loss of support by neurotrophic factors. These examples
illustrate the conservation and divergence in the ways that death pat
hways are composed and ordered. (C) 1997, Elsevier Science Inc.