B7-h3 (B7 homolog 3 protein), also known as CD276, is an important immune checkpoint molecule in the B7-CD28 family. It is a type I transmembrane glycoprotein consisting of 316 amino acids and contains a putative 28AA signal peptide, a 217AA extracellular region composed of immunoglobulin constant (IgC) and variable (IgV) structures, a transmembrane region, and a 45-amino acid cytoplasmic domain. B7-H3 is a T cell co-suppressor molecule with partial co-stimulatory function. B7-H3 can effectively inhibit the function of T cells and NK cells, and also play a role in bone development. The expression of B7-H3 is low in normal tissues and is found in a variety of malignant tumors, which is closely related to the growth, metastasis, recurrence and poor prognosis of malignant tumors. B7-H3 can down-regulate T-assisted type 1 mediated immune response, inhibit CD4+T cell activation and inhibit cytokine production, and thus may play a role in promoting immune escape of cancer cells.
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