Figure 2From: T-cell co-stimulatory pathways in autoimmunityActivation-induced co-stimulatory receptors and their ligands. Upon activation, T cells express a number of receptors that have co-stimulatory ability and are important for sustained activation, proliferation, and differentiation. Their ligands again are expressed on antigen-presenting cells. ICOS, inducible co-stimulator; MHC, major histocompatibility complex; TCR, T-cell receptor.Back to article page