Prion diseases, blood and the immune system: concerns and reality.

There is a great amount of uncertainty about the nature of the agent which causes spongiform encephalopathies. In recent years the occurrence of bovine spongiform encephalopathy and of new variant-Creutzfeldt Jakob disease, has raised concerns that prions may, under certain circumstances, contaminate the blood supply. This review article illustrates the problems with which research in this field is fraught, and presents some of the arguments which are controversially discussed in the field.