A novel nickel avidin-biotin-peroxidase method for histochemical visualization of neurofibrillary tangles, senile plaques, and neuropil threads.

A reliable new method was developed for detecting neurofibrillary tangles, senile plaques, and neuropil threads in human neural tissue. Excellent morphological definition of the pathological structures was achieved with this procedure without staining normal neuronal and glial elements. The technique was applied to cortical tissue from eight patients with Alzheimer's disease and three controls. Histological sections from these cases were incubated in an avidin-biotin-peroxidase complex solution containing 0.5% nickel ammonium sulfate, followed by visualization in 3,3'-diaminobenzidine and H2O2. Although the avidin-biotin system is routinely used in immunohistochemistry, no antibodies were employed in the present procedure. This technique has advantages over silver impregnation methods because it requires very little monitoring of critical steps and yields superior results. The method is suitable for processing large numbers of tissue sections per staining run, and the results are highly reproducible. These features are advantageous in research studies comparing the distribution of lesions in large numbers of cases. The precise mechanism of staining has not been determined; however, conditions such as nickel concentrations, pH, and avidin-biotin-peroxidase complex concentrations were varied to examine critical steps in the process.