The expansive role of CD40 and its ligand, gp39, in immunity.

The interactions between CD40 and its ligand, gp39, are central to the development and maintenance of immunity. The role this receptor-ligand pair plays in B cell activation, isotype switching and memory generation has been firmly established through the study of in vitro and in vivo murine models, as well as human in vitro systems and immunodeficiencies. In this review, the potential role of gp39 in the regulation of co-stimulatory molecules and their implications on thymic education and peripheral tolerance are discussed.