Localization and cell association of C1q in Alzheimer's disease brain
Abstract
The complement protein, C1q, has been shown to bind to fibrillar beta-amyloid, resulting in the activation of the classical complement pathway. C1q has also been found associated with most but not all amyloid deposits in brain. To determine whether C1q is exclusively associated with plaques containing the fibrillar form of beta-amyloid, normal and Alzheimer brain were immunohistochemically double labeled using thioflavine, which specifically stains beta-amyloid in a beta-sheet conformation, and an affinity- purified antibody to human C1q. C1q immunostaining was colocalized with nearly all thioflavine-positive plaques, while C1q was not detected in beta-amyloid immunopositive plaques which were thioflavine-negative. Beta-amyloid plaques in nondemented controls (which are typically thioflavine-negative) were also negative for C1q. Microglia and astrocytes of reactive morphology were also associated with C1q-positive plaques and neurons. Interestingly, many neuronal cells in the AD brain, but not microglia or astrocytes, stained prominently with anti-C1q. Neurons in control brain were not C1q positive. Our data suggest that some of these C1q-positive structures were neurofibrillary tangles immunoreactive for hyperphosphorylated ta...Continue Reading
Citations
Complement C3 and C4 expression in C1q sufficient and deficient mouse models of Alzheimer's disease.
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