Human CTLA4 Protein, ECD (extracellular domain), Recombinant

Description :
Cytotoxic T-lymphocyte antigen 4 (CTLA4), aslo known as CD152, is a single pass type I transmembrane glycoprotein of the Ig superfamily. It is composed of an IgV-type extracellular domain, a transmembrane domain, and a cytoplasmic tail. CTLA4 is the founding member of the CD28/CTLA-4 family. Members of the CD28/CTLA-4 family either promote T cell activation (CD28 and ICOS) or inhibit T cell activation (CTLA4 and PD­1). Both CTLA-4 and CD28 bind to the same B7 family ligands, CD80/B7-1 and CD86/B7-2. CTLA-4 binds to B7-1 and B7-2 with a 20-100 fold higher affinity than CD28. The CTLA4 gene is widely expressed with highest levels in lymphoid tissues. It is detected in activated T-cells where expression levels are 30- to 50-fold less than CD28 on the cell surface following activation. Mutations in CTLA4 gene is associated with insulin-dependent diabetes mellitus, Graves disease, Hashimoto thyroiditis, celiac disease, systemic lupus erythematosus, thyroid-associated orbitopathy, and other autoimmune diseases. Alternate transcriptional splice variants, encoding different isoforms of CTLA4, have been characterized. The membrane-bound isoform functions as a homodimer interconnected by a disulfide bond, while the soluble isoform functions as a monomer. The engineered CTLA4-Fc fusion proteins inhibit T-cell-dependent immune responses and are used as immunosuppressive agents by acting as a competitive inhibitor of CD28. Blockade of CTLA4 inhibitory activity with monoclonal antibodies enhances antitumor immunity and has been proven to be an effective approach for cancer immunotherapy.