[Clinical and biological features of haptoglobin phenotypes]

Haptoglobin is a late positive acute phase protein of inflammation. Haptoglobin binds to free hemoglobin released from erythrocytes during intravascular hemolysis to form a complex which is removed shortly. Other properties like inhibition of oxidative stress and prostaglandin synthesis have been described. Three main phenotypes of haptoglobin have been identified: Hp1-1, Hp2-1, Hp2-2, which may have an impact in different diseases such as cardiovascular or infectious diseases. Haptoglobins of different phenotypes can be separated by capillary electrophoresis. They may induce a split of the alpha 2-globulin zone in the electrophoretic pattern. Hp1-1 and Hp2-1 phenotypes induce an important and a moderate split of the α2 globulin zone, respectively, whereas Hp2-2 does not. In vitro hemolysis and migration of a monoclonal component (i.e. immunoglobulin free light chain) may also induce a split of the alpha 2-globulin zone. In daily practice, Hp2-1 or Hp1-1 phenotypes could be notified in the electrophoresis report to alert the clinician about the possible physiopathological consequences.