CTLA4 Signaling Pathway

CTLA4, also known as CD152, is a member of the immunoglobulin superfamily. CTLA4 is a T cell surface transmembrane protein encoded by the CTLA4 gene and is expressed mainly on the surface of activated CD4+ and CD8+ T lymphocytes as well as activated B lymphocytes. The human CTLA4 gene is located in the long arm 33 band of chromosome 2 and contains four exons encoding the leader sequence, the ligand binding region, the transmembrane region, and the cytoplasmic tail region, respectively. CTLA4 has two subtypes: full-length CTLA4 (flCTLA4) encoded by four exons and soluble CTLA4 (sCTLA4) encoded by three exons other than the transmembrane region. sCTLA4 is derived from an alternative splicing that results in the loss of a cysteine residue and is a soluble monomeric protein present in serum. Activated T cells have low expression of sCTLA4 protein and high expression of flCTLA4 protein.