Lack of proapoptotic activity of soluble CD95 ligand is due to its failure to induce CD95 oligomers.

CD95 and CD95 ligand (CD95L) are critical molecules of the immune system. They play an important role in regulating T cell apoptosis. The membrane form of CD95L can be cleaved to release a soluble version, which possesses reduced apoptotic activity. In this study, we formally demonstrate that the reduced activity of soluble CD95L is due to its inability to oligomerize the CD95 receptor, an event that is critical for initiating death signaling from the receptor.