Cortical inflammation in Alzheimer disease but not dementia with Lewy bodies

Background: There have been no previous studies on the role of inflammation in the brain for the second most common dementing disorder, dementia with Lewy bodies. Objective: To investigate the degree of cortical inflammation in dementia with Lewy bodies (DLB) compared with Alzheimer disease (AD) and control brains. Design and Main Outcome Measures: Postmortem tissue collection from a brain donor program using standardized diagnostic criteria. Brains collected from January 1, 1993, through December 31, 1996, were screened and selected only for the presence or absence of tau neuritic plaques. Results of immunohistochemistry for HLA-DR were quantified using area fraction counts. Counts were performed by investigators who were unaware of the diagnosis. Results were compared across groups using analysis of variance and posthoc testing. Setting: A medical research institute in Sydney, Australia. Patients: Eight brains with DLB and without the tau neuritic plaques typical of AD, 10 brains with AD and no Lewy bodies, and II nondemented controls without significant neuropathological features were selected from a consecutive sample. Results: Compared with AD, DIB demonstrated significantly less inflammation in the form of HLA-DR-reactive microglia in all cortical regions (P<.001, posthoc). The level of inflammation in DLB was comparable to that seen in controls (P=.54, post hoc). Conclusions: Inflammation appears related to the tau neuritic plaques of AD. Despite similar clinical presentations, therapeutic anti-inflammatory strategies are not likely to be effective for pure DLB.