Anti-protein S antibodies are used for the immunodetection of the protein encoded by the PROS1 gene. In humans, the canonical protein has a reported length of 676 amino acid residues and a mass of 75.1 kDa. It is known to be a secreted protein. It is notably expressed in plasma. Post-translational modifications have been described, including glycosylation. The gene encoding this protein is implicated in Thrombophilia due to protein S deficiency. Other names for this target antigen include PS21, PS22, PS23, PS24, PS25, PSA, THPH5, and PROS. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species. A number of protein S antibodies have been mentioned in research publications and have associated citations. Western Blot is a widely used application for these antibodies. ELISA and Immunohistochemistry are also common applications.