B7-H3/CD276 Extracellular Domain (human, recombinant)

B7-H3, also known as CD276, is a type I transmembrane glycoprotein and member of the B7-CD28 immune checkpoint protein family with roles in the T cell-mediated immune response.^1,2 It is encoded by CD276 in humans and is composed of an N-terminal signal peptide, an extracellular domain containing two identical pairs of immunoglobulin (Ig) constant (IgC) and variable (IgV) domains, a transmembrane region, and an intracellular tail. CD276 is ubiquitously expressed, however, protein expression is post-transcriptionally regulated.² B7-H3 protein is constitutively expressed on non-immune fibroblasts, endothelial cells, and osteoblasts, and can be induced in immune cells such as dendritic cells, macrophages, natural killer (NK) cells, and T cells. It inhibits NK cell-mediated lysis, as well as induces co-inhibition of T cells, increases activation of tumor-specific cytotoxic T cells, and decreases proliferation of CD4⁺ and CD8⁺ T cells through modulation of nuclear factor of activated T cells (NFAT), NF-κB, and AP-1. Serum levels of B7-H3 are increased in patients with sepsis, as are intestinal levels in patients with graft versus host disease. High tumor levels of B7-H3 protein are associated with increased tumor size, poorly differentiated tumors, lymph invasion, and shorter overall survival in patients with lung and breast cancers.³ Cayman's B7-H3/CD276 Extracellular Domain (human, recombinant) protein is a disulfide-linked homodimer. The reduced monomer, comprised of B7-H3 (amino acids 1-461) fused to human IgG1 Fc at its C-terminus, consists of 673 amino acids, has a calculated molecular weight of 73.4 kDa, and a predicted N-terminus of Gly27 after signal peptide cleavage. As a result of glycosylation, the monomer migrates at approximately 116 kDa by SDS-PAGE under reducing conditions.

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1. Li, G., Quan, Y., Che, F., et al. B7-H3 in tumors: friend or foe for tumor immunity? Cancer Chemother. Pharmacol. 81(2), 245-253 (2018).

2. Janakiram, M., Shah, U.A., Liu, W., et al. The third group of the B7-CD28 immune checkpoint family: HHLA2, TMIGD2, B7x, and B7-H3. Immunol. Rev. 276(1), 26-39 (2017).

3. He, L., and Li, Z. B7-H3 and its role in bone cancers. Pathol. Res. Pract. 215(6), 152420 (2019).