CD278

CD278 also known as Inducible T-cell COStimulator (ICOS) is a protein that in humans is encoded by the ICOS gene. ICOS is a member of the CD28 and CTLA-4 cell-surface receptor family. It is an immune checkpoint and stimulates T-cell proliferation and cytokine production.

Structure

The ICOS protein is a homodimeric protein that is a member of the immunoglobulin superfamily. It is composed of two identical chains, each containing two extracellular domains: an immunoglobulin variable (IgV) domain and an immunoglobulin constant (IgC) domain.

Function

ICOS is expressed on activated T cells and binds to its ligand, B7RP-1, on antigen-presenting cells. This interaction provides a costimulatory signal that is essential for T cell proliferation and production of IL4, IL5, and IL13. It also plays a key role in the development of follicular T helper cells (Tfh), a subset of T cells involved in the production of antibodies by B cells.

Clinical significance

Abnormal ICOS function has been associated with a number of autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis. In addition, ICOS is a potential target for immunotherapy in cancer, as blocking its function can enhance the anti-tumor response of T cells.

See also

• CD28
• CTLA-4
• T-cell
• Cytokine
• Autoimmune diseases
• Immunotherapy