Evidence for activation of microglia in patients with psychiatric illnesses

Activation of microglia/macrophages is a key event in response to pathologi cal changes in the CNS. HLA-DR is a valuable immunohistochemical marker tha t specifically reacts with activated microglia cells. In order to elucidate a potential role of microgliosis in severe psychiatric illnesses, post-mor tem frontal cortex and hippocampus of patients with schizophrenia (n = 14) and affective disorder (n = 6) and control specimens (n = 13) were studied. Additionally Alzheimer's disease cases (n = 8) were included as a human mo del system with typical neurodegenerative alterations and microglia activat ion. All patient groups revealed subjects with abundant microglia immunosta ining (schizophrenia, three patients; affective disorder, one patient; Alzh eimer's disease, four patients) in both gray and white matter. This finding provides evidence for distinct neuropathological changes in brains of pati ents with schizophrenia and affective disorder. The activation of microglia cells, which represent a major part of the brain immune response, may help to unravel the pathophysiological processes in severe psychiatric illnesse s. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.