Figure 1. Coinhibitory pathways in the B7-CD28 family.
T cell activation is initiated by recognition of peptide antigens presented by APCs to the TCR CD3 complex and T cell costimulatory signals provided by CD28 interactions with CD80 and CD86. Upon T cell activation, many coinhibitory pathways are upregulated and can attenuate TCR and costimulatory signals. Coinhibitory pathways in the B7-CD28 family control responses of naive, effector, regulatory and exhausted T cells. These receptors are expressed on T cells and some are also expressed on other hematopoietic cells, as described in the text. Their ligands can be expressed on APCs, non-hematopoietic cells and in tumors; some molecules are expressed on both APCs and T cells (indicated by *). Binding partners for B7-H3, B7-H4, VISTA, and BTNL2 have not yet been identified.
