Accumulation of prion protein in tonsil and appendix: review of tissue samples.

Variant Creutzfeldt-Jakob disease is almost certainly caused by the bovine spongiform encephalopathy agent, and although the disease is rare (115 deaths to date) there is uncertainty about future numbers of cases. The lack of a conventional immune response and the inability to detect abnormal prion protein in blood has hampered the development of a blood test. Lymphoreticular accumulation of prion protein has been used as a preclinical test for scrapie (the form of the disease in sheep and goats) and is a consistent feature of variant Creutzfeldt-Jakob disease, occurring before the onset of symptoms. We screened large numbers of specimens from appendicectomies and tonsillectomies for the presence of prion protein in lymphoreticular tissue to determine the number of people with preclinical variant Creutzfeldt-Jakob disease.