How do tumor necrosis factor receptors work?

Quite suddenly, a new level of understanding has been attached to the TNF ligand and receptor families. Many of the proximal transducers that signal the presence of TNF or its homologs have been identified, and certain components of the distal signaling pathway have emerged as well. We lack, however, a "movie" of the events that transpire when TNF binds its receptors on the surface of a cell. The facts in hand permit an educated approximation.