UNIT 11.9C Apoptosis Signaling Pathways

  1. Richard M. Siegel,
  2. Michael J. Lenardo

Published Online: 1 NOV 2002

DOI: 10.1002/0471142735.im1109cs44

Current Protocols in Immunology

Current Protocols in Immunology

How to Cite

Siegel, R. M. and Lenardo, M. J. 2002. Apoptosis Signaling Pathways. Current Protocols in Immunology. 44:11.9C:11.9C.1–11.9C.10.

Author Information

  1. National Institute of Allergy & Infectious Diseases, Bethesda, Maryland

Publication History

  1. Published Online: 1 NOV 2002
  2. Published Print: AUG 2002


In the past few years much has been learned about the molecular signals governing apoptosis, or programmed cell death, in lymphocytes and other cells of the immune system. Two major pathways, active and passive apoptosis, have been identified and are discussed in this overview. Active apoptosis, also termed propriocidal cell death or antigen-induced cell death, occurs when cells are stimulated through a family of TNF-related receptors termed death receptors. These receptors are up-regulated in activated lymphocytes and trigger apoptosis chiefly in effector cells that have been recently stimulated through the antigen receptor. Passive or lymphokine withdrawal apoptosis occurs when activated lymphocytes are deprived of essential growth cytokines and does not require death receptors. Cell death initiated by either pathway is carried out by a unique family of intracellular cysteine proteases, the caspases. Defects in each of these pathways produce distinct pathologies.