Anti-Haptoglobin antibodies are used for the immunodetection of the protein encoded by the HP gene. In humans, the canonical protein has a reported length of 406 amino acid residues and a mass of 45.2 kDa. It is known to be a secreted protein. Alternative splicing is reported to yield 2 different isoforms for this protein. It is notably expressed by the liver and secreted in plasma. It is a member of the Peptidase S1 protein family. Post-translational modifications have been described, including glycosylation. The gene encoding this protein is implicated in Anhaptoglobinemia. Other names for this target antigen include HP2ALPHA2, HPA1S, binding peptide, haptoglobin alpha(1S)-beta, haptoglobin alpha(2FS)-beta, and BP. Gene orthologs have been identified in the mouse species.