B7-H3

B7-H3, also known as CD276, is a protein that in humans is encoded by the CD276 gene. It is a member of the B7 family of immune checkpoint molecules, which are involved in the regulation of immune responses. B7-H3 is expressed on a variety of cells, including antigen-presenting cells, and plays a role in modulating T-cell responses.

Structure and Function

B7-H3 is a type I transmembrane protein that belongs to the immunoglobulin superfamily. It consists of an extracellular region with two immunoglobulin-like domains, a transmembrane domain, and a short cytoplasmic tail. The exact function of B7-H3 is not fully understood, but it is known to have both stimulatory and inhibitory effects on T-cell responses, depending on the context.

B7-H3 is involved in the regulation of immune responses, particularly in the context of cancer. It is often overexpressed in various types of tumors, where it may contribute to immune evasion by inhibiting T-cell activation and proliferation. This makes B7-H3 a potential target for cancer immunotherapy.

Expression

B7-H3 is expressed on a wide range of cells, including:

• Dendritic cells
• Monocytes
• T cells
• B cells
• Various non-immune cells, such as fibroblasts and epithelial cells

In the context of cancer, B7-H3 is frequently overexpressed on tumor cells and tumor-associated vasculature, which has been associated with poor prognosis in several types of cancer, including breast, prostate, and lung cancer.

Clinical Significance

Due to its role in immune regulation and its expression in tumors, B7-H3 is being investigated as a target for cancer immunotherapy. Several therapeutic strategies are being explored, including:

• Monoclonal antibodies targeting B7-H3
• Antibody-drug conjugates
• Chimeric antigen receptor (CAR) T-cell therapies

These approaches aim to enhance the immune system's ability to recognize and destroy cancer cells by blocking the inhibitory signals mediated by B7-H3.

Research and Development

Ongoing research is focused on understanding the precise mechanisms by which B7-H3 modulates immune responses and its role in tumor biology. Clinical trials are underway to evaluate the safety and efficacy of B7-H3-targeted therapies in various cancers.

Also see

• Immune checkpoint
• Cancer immunotherapy
• T-cell activation
• Monoclonal antibody