Finding our way through the ‘neuroinflammation’ fog

'Neuroinflammation', a widely used neuroscience term, has no generally accepted neuropathological tissue correlates. On the other hand, 'inflammation', is characterized by the presence of perivascular infiltrates of cells of the adaptive immune system and is indeed observed in the CNS. To address this nomenclatorial confusion, we analyzed in a hypothesis-free manner the molecular profiles of neuropsychiatric and inflammatory conditions. Using two different computational approaches, we have examined whether unsupervised analysis of microarray data from cerebral cortex of Alzheimer's, Parkinson's and schizophrenia patients show similar molecular signatures with recognized inflammatory conditions such as multiple sclerosis. We show that the gene sets with altered expression are very different across these two disease groups. Our results indicate that 'inflammation' and 'neuroinflammation' represent different categories both at the histophenotypic and transcriptomic level and are not interchangeable.