CD80

CD80 (Cluster of Differentiation 80) is a protein found on the surface of antigen-presenting cells (APCs) such as dendritic cells, B cells, and macrophages. It plays a crucial role in the activation of T cells and the initiation of the immune response.

Structure

CD80 is a member of the immunoglobulin superfamily and is encoded by the CD80 gene located on chromosome 3 in humans. The protein consists of an extracellular domain, a transmembrane domain, and a cytoplasmic tail. The extracellular domain contains two immunoglobulin-like domains that are essential for its interaction with other molecules.

Function

CD80 functions primarily as a costimulatory molecule that provides necessary signals for T cell activation and survival. It binds to CD28 and CTLA-4 (Cytotoxic T-Lymphocyte Antigen 4) on T cells. The interaction between CD80 and CD28 provides a positive costimulatory signal that promotes T cell activation, proliferation, and cytokine production. Conversely, the interaction between CD80 and CTLA-4 delivers an inhibitory signal that downregulates T cell responses, maintaining immune homeostasis and preventing autoimmunity.

Expression

CD80 is expressed on the surface of antigen-presenting cells upon activation by various stimuli, including pathogen-associated molecular patterns (PAMPs) and cytokines. Its expression is tightly regulated to ensure appropriate immune responses.

Clinical Significance

The CD80-CD28/CTLA-4 pathway is a critical target for immunotherapy in various diseases, including autoimmune disorders, transplant rejection, and cancer. Blockade of the CD80-CTLA-4 interaction with immune checkpoint inhibitors such as ipilimumab has shown efficacy in enhancing anti-tumor immunity.

See Also

• CD28
• CTLA-4
• Antigen-presenting cell
• T cell
• Immune response
• Immunotherapy