Molecular mechanisms of CD40 signaling.

CD40, a member of the growing tumor necrosis factor receptor (TNF-R) family of molecules, functions as a transmembrane signal receptor in both hematopoietic and non-hematopoietic cell types, although its physiological roles are less well understood in the latter. Much has been learned over the past decade about the role of CD40 signaling in various cellular functions. In addition, some of the molecular events which occur subsequent to CD40 engagement have been characterized, although much remains to be understood. This review will summarize the known important biological roles of CD40, and discuss what is currently known about how CD40 signals.