B7-H3, also known as CD276. B7-H3 is a type I transmembrane protein belonging to the B7 family of immune checkpoint molecules. Unlike its relatives PD-L1 (B7-H1) or B7-H4, B7-H3's exact receptor on T cells and its precise role in immune regulation remain less clearly defined. However, it is broadly and highly overexpressed on a wide range of solid tumors—including prostate cancer, melanoma, non-small cell lung cancer, and glioblastoma—while showing limited expression in most normal tissues.