CTLA-4 is a member of the immunoglobulin superfamily and encodes a protein which transmits an inhibitory signal to T cells. The protein contains a V domain, a transmembrane domain, and a cytoplasmic tail. Alternate transcriptional splice variants, encoding different isoforms, have been characterized. The membrane-bound isoform functions as a homodimer interconnected by a disulfide bond, while the soluble isoform functions as a monomer. Mutations in this gene have been associated with insulin-dependent diabetes mellitus, Graves disease, Hashimoto thyroiditis, celiac disease, systemic lupus erythematosus, thyroid-associated orbitopathy, and other autoimmune diseases.
Cytotoxic T-Lymphocyte Associated Antigen-4 Human Recombinant produced in insect cells is a homodimeric, glycosylated, polypeptide chain containing a total molecular mass of 80 kDa. Each subunit (40kDa) is fused to a polypeptide linker to the Fc portion of Human IgG1. CTLA4 is expressed in low copy number by T-cells only after activation, but it binds CD28-ligand with approximately 20-fold higher affinity than CD28. A soluble form of the extracellular domain of CTLA-4 has been shown to bind CD28-ligand with high avidity and to suppress T-cell-dependent antibody responses in vivo.
Large doses of this soluble protein also suppress responses to a second immunization. CTLA-4 is purified by proprietary chromatographic techniques.
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