BIOLOGICAL FUNCTIONS OF HAPTOGLOBIN - NEW PIECES TO AN OLD PUZZLE

Haptoglobin, an ''acute phase'' protein, has different functions, whic h display genetic polymorphism. The complex of haptoglobin with haemog lobin is metabolized in the heaptic reticuloendothelial system. Biosyn thesis of haptoglobin occurs not only in the liver, but also in adipos e tissue and in lung, providing antioxidant and antimicrobial activity . Changes in the measured concentrations of haptoglobin in serum may h elp to assess the disease status of patients with inflammations, infec tions, malignancy etc. (increases) as well as in haemolytic conditions (decreases). Haptoglobin plays a role in stimulation of angiogenesis and has highly potent cholesterol-crystallization-promoting activity. Probably the most important biological function of haptoglobin consist s in the host defence responses to infection and inflammation, acting as a natural antagonist for receptor-ligand activation of the immune s ystem.