Anti-CTL4 antibodies enable researchers to detect and measure the CTL4 antigen in biological samples. This target is a reported synonym of the SLC44A4 gene, which encodes solute carrier family 44 member 4. This protein is known to function in transmembrane transport, among other biological roles. The human version of CTL4 has a canonical amino acid length of 710 residues and a protein mass of 79.3 kilodaltons, although 4 isoforms have been identified. It is reported to be localized in the cell membrane of cells and notably expressed in many tissues, such as the bronchus and fallopian tube. CTL4 is a member of the CTL (choline transporter-like) protein family.