B7-H3 is a member of the B7 gene family. It has 88% amino acid sequence identity with mouse B7-H3. It is mostly expressed on professional APCs, including B cells, macrophages, and dendritic cells. Its expression on dendritic cells appears to be up-regulated by LPS. B7-H3 protein inhibits T cell activation and cytokine production. It was reported that monoclonal antibody against B7-H3 enhanced T cell proliferation in vitro and led to exacerbated EAE in vivo. Therefore, B7-H3 may be a negative regulator on T cell activation and function.