Regulation of immune and autoimmune responses by ICOS–B7h interaction

Proper T cell activation and function are regulated by the innate immune system, importantly through positive and negative costimulatory molecules of the B7 superfamily. Inducible costimulator (ICOS) is expressed on T cells after T cell activation. A ligand for ICOS, B7h (also known as B7RP-1), is expressed on B cells and induced in nonlymphoid tissues by TNF-α. The wide distribution of B7h may play essential roles in different phases and types of immune function. In this review, we summarize the latest data about inducible costimulator and its receptor and their roles in regulation of immune and autoimmune responses.