详细描述：
CTLA-4 (CD152) 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 also 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. CTLA-4 is expressed in low copy number by T-cells only after activation, but it binds the 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 the CD28 ligand with high affinity and to suppress T-cell-dependent antibody responses in vivo. Large doses of this soluble protein also suppress responses to a second immunization. |Human recombinant CTLA-4 produced in insect cells is a homodimeric, glycosylated polypeptide chain( having a total molecular mass of 80 kDa. Each subunit (40 kDa) is fused via a polypeptide linker to the Fc portion of human IgG1. It has been purified by using proprietary chromatographic techniques.
