B7-H3/CD276

B7-H3, formally the CD276 antigen, belongs to the B7 family of immune regulators and circulates predominantly as the 4Ig-B7-H3 splice variant with tandem IgV-IgC pairs. It is expressed on dendritic cells, monocytes and many non-hematopoietic tissues; protein levels in healthy organs are low, whereas frequent overexpression occurs in lung, prostate, ovarian and pediatric solid tumors. Functionally, B7-H3 is generally regarded as an inhibitory checkpoint that dampens T cell responses, although its receptor assignments remain less settled than for PD-L1. This tumor-restricted expression pattern has made CD276 one of the most actively pursued next-generation antibody, antibody-drug conjugate and CAR-T targets in oncology.