Human B7 homolog 3 (B7-H3) is a member of the B7 family of immune proteins that provide signals for the regulation of immune responses. Other family members include B7-1, B7-2, B7-H1/PD-L1, B7-H2, and PD-L2. B7 family proteins are type I transmembrane immunoglobulin (Ig) superfamily members that contain extracellular Ig Vlike and Ig Clike domains with a short cytoplasmic tail. Termed 4IgB7-H3 or B7-H3b, this molecule has two additional Ig-like domains (one Vtype and one Ctype) and shows a ubiquituous expression pattern.
