Anti-CSK antibodies are used in the immunodetection of the protein C-terminal Src kinase. In humans, the canonical protein has a reported length of 450 amino acid residues and a mass of 50.7 kDa. Its subcellular localization is in the cell membrane and cytoplasm. It is reported to be expressed in the lung and macrophages. A member of the Tyr protein kinase protein family, CSK is known to be involved with adaptive immune responses and brain development. Post-translational modifications have been described, including phosphorylation. Synonyms for this target antigen include C-Src kinase, CSK, non-receptor tyrosine kinase, c-src tyrosine kinase, protein-tyrosine kinase CYL, and tyrosine-protein kinase CSK. CSK gene orthologs have been reported in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species. Over 60 citations in the literature describe the use of Csk antibodies in research. Western Blot is a widely used application for these antibodies. ELISA, Immunofluorescence, and Immunohistochemistry are also common applications.