Immunohistochemistry using antibodies to alpha-interferon and its induced protein, MxA, in Alzheimer's and Parkinson's disease brain tissues.

The localization of alpha-interferon (alpha-IFN) and its induced protein, MxA, was examined in human brain tissues from neurologically normal, Alzheimer's disease (AD) and Parkinson's disease (PD) cases. In all cases, a few neurons in the superficial cortical layers and microglial cells in the white matter were stained with the antibody to alpha-IFN. In AD brains, white matter microglia were intensely labeled for alpha-IFN and reactive microglia, such as those on senile plaques, were strongly positive for MxA protein. In PD, Lewy bodies in the substantia nigra were positive for MxA, but there was no staining for alpha-IFN in that region. These results suggest that increased expression of alpha-IFN in the white matter microglia and appearance of MxA protein in reactive microglia contribute to Alzheimer pathology. The staining of some Lewy bodies for MxA may be indicative of a viral infection or other unknown factor.