Ubiquitin immunoreactivity in kuru plaques in Creutzfeldt-Jakob disease. Cerebellar kuru plaques in 2 cases of Creutzfeldt-Jakob disease were studied immunohistochemically. Similar to cerebellar senile plaques in Alzheimer's disease, many kuru plaques contained ubiquitin-positive, tau-negative small granular elements, presumably representing dystrophic neurites. Our results suggest that similar mechanisms are involved in neuritic changes in cerebellar plaques in Creutzfeldt-Jakob and Alzheimer's diseases despite differences of amyloid proteins in the plaques. 