Haemoglobin scavenger receptor: function in relation to disease.

Highly efficient systems remove the toxic and proinflammatory haemoglobin from the circulation and local sites of tissue damage. Macrophages are major haemoglobin-clearing cells; CD163 was recently recognized as the specific haemoglobin scavenger receptor (HbSR). It is tightly involved in both physiological as well as pathophysiological processes, such as cytoprotection and inflammation. Haemoglobin functions as a double-edged sword. In moderate quantities and bound to haptoglobin, it forms a ligand for haemoglobin scavenger receptor CD163/HbSR, but when unleashed in large amounts, it can become toxic by mediating oxidative stress and inflammation. CD163/HbSR plays a crucial role in the control of inflammatory processes, probably in part through its effects on both ferritin induction and subsequent induction of antiinflammatory pathways through interleukin-10 and haem oxygenase. Besides the observation that the haemoglobin scavenger receptor provides a promising target for new treatment possibilities, it offers a novel view on the aetiology of diverse physiological as well as pathophysiological processes. In addition, monocyte CD163/HbSR and soluble CD163/HbSR are potential diagnostic tools in a variety of disease states, such as inflammation, atherosclerosis, transplant rejection, and carcinoma.