Presence of neurofilament protein in Alzheimer's neurofibrillary tangles (ANT)

Abstract

Localization of neurofilament (NF) protein in the neurons of rat's brain, spinal cord, and peripheral nerves was studied by the indirect immunofluorescent method using goat-antirabbit plus rabbit anti-NF antibody. The NF protein was purified from the calf brain by the method of Yen et al. (1976). Control sections were treated with nonspecific rabbit serum and with the experimental rabbit serum absorbed with the NF protein. Fluorescence in the axons of the neurons, such as the motor neurons of the spinal cord, peripheral nerves, pontine nuclei, or those of the cerebellar cortex including Purkinje cells, was strong, while that of the dendrites and perikarya was weaker. Glial processes also showed intense fluorescence. Fluorescence in glia cells was interpreted as representing an insufficient separation of NF protein as the antigen from the glial fibrillary acidic protein (GFA). Localization of NF protein in the Alzheimer's neurofibrillary tangles (ANT) in the hippocampus of the brain of a patient with Alzheimer's disease, was examined by the same way as described above. ANT showed the whole gamut of the color of fluorescence from completely positive green to mixed green with increasingly bluer tints. Astroglial processes also showed intense green fluorescence. The results suggest that ANT comprises NF protein as the structural component and that the increasingly blue fluorescence may represent fewer antigenic sites due to increasing degrees of structural insolubilization or aging of ANT. Possibility of crosslinkage between NF protein and contribution of pathological factors as the cause of ANT formation were discussed.