Cell Death and Differentiation (2003) 10, 1215–1225 & 2003 Nature Publishing Group All rights reserved 1350-9047/03 $25.00 www.nature.com/cdd Review CD95 ligand - death factor and costimulatory molecule? O Janssen*,1, J Qian1, A Linkermann1 and D Kabelitz1 Tissue and Cellular Expression of CD95L 1 Institute for Immunology, Medical Center Schleswig-Holstein, Campus Kiel, Michaelisstrasse 5, D-24105 Kiel, Germany The CD95 ligand (CD95L, Apo-1L, FasL, CD178) is a 281- * Corresponding author: O Janssen. Tel: þ 49-431-5973377; Fax: þ 49-431- amino-acid-containing type II transmembrane protein of the 5973335; E-mail:
[email protected] TNF family of death factors (Figure 1).1 Its death-inducing function is best documented in the context of activation- Received 24.4.03; revised 12.6.03; accepted 20.6.03; published online 1 August 2003 induced cell death (AICD) in T cells.2 CD95L is expressed as a Edited by T Ferguson death factor in cytotoxic T lymphocytes (CTL) to kill virally infected or transformed target cells and in natural killer (NK) cells, where it is upregulated by CD16 engagement and 3 Abstract cytokines including IL-2 and IL-12. Similarly, high levels of intracellular CD95L have been detected in monocytic cells The CD95 ligand is involved as a death factor in the with an inducible release upon activation.4 Under physiologi- regulation of activation-induced cell death, establishment cal conditions, CD95L is implicated in the control of erythroid of immune privilege and tumor cell survival. In addition, differentiation,5 angiogenesis in the eye6 and skin home- 7 CD95L may serve as a costimulatory molecule for T-cell ostasis.