Neocortical neuronal subpopulations labeled by a monoclonal antibody to calbindin exhibit differential vulnerability in Alzheimer's disease.

Numerous studies have demonstrated that specific neuronal subtypes display a differential vulnerability to the pathological process in Alzheimer's disease. Large pyramidal neurons are likely to be highly vulnerable, whereas smaller neurons are more resistant to pathology. Using a monoclonal antibody to the calcium-binding protein calbindin, we observed in the human prefrontal cortex distinct populations of labeled cells. First, a subset of heavily stained interneurons was located in layers II and superficial III and in layers V-VI. Second, a subpopulation of pyramidal neurons in the mid and deep parts of layer III displayed a less intense, punctate staining pattern. The interneurons in the superficial layers were unaffected in the Alzheimer's disease cases. Interestingly, in layers V-VI, there was significant cell loss in the interneuron population, but only in the Alzheimer's disease cases with high neurofibrillary tangle densities. The calbindin-immunoreactive pyramidal neurons of layer III were dramatically affected in the disease. Moreover, there was a strong correlation between the extent of the loss of these cells and neurofibrillary tangle counts. These data suggest that calbindin is present in multiple neuronal subpopulations that exhibit a differential vulnerability in Alzheimer's disease and support the hypothesis that the degenerative process involves specific neuronal subsets with particular anatomical and molecular profiles.