Haptoglobin is an alpha2-globulin plasma protein synthesized in the liver. It is an acute phase protein which also acts as a scavenger of hemoglobin from hemolyzed red cells. The haptoglobin monomer consists of two alpha and two beta chains; the alpha chains may be hp1Fa, hp1Sa or hp2a types while the beta chain is constant. Three major phenotypes are recognized: Hp1-1, Hp-2-1 and Hp-2-2, in which the hp1a chain may be either the F or S type. This antibody reacts with human haptoglobin from pooled plasma.