[Histonet] Astrocyte immunohistochemical marker

[John Kiernan]

Immunostaining for GFAP has been the definitive method for astrocyte cytoplasm for 30 years, and good primary antibodies have been around for at least 20 years. The distinction between different kinds of astrocyte is made by staining with serial dilutions of the primary antiserum. Reactive astrocytes have the highest concentrations of glial fibrillary acidic protein (GFAP) in their cytoplasms, and are immunostained by greatly diluted antisera. Normal fibrous astrocytes (in normal white matter and also with processes abutting ependyma, pia and small blood vessels) also contain plenty of GFAP, but are unlikely to be confused with astrocytes around a site of injury or in a tumour. Normal protoplasmic (or velate) astrocytes extend their processes into normal white and grey matter; their cytoplasm contains less GFAP than the cytoplasm of astrocyte in normal white matter. 

To detect reactive astrocytes you need to do serial dilutions of the primary antibody on sections of normal CNS. For detecting gliosis, use the dilution that fails to stain GFAP in grey matter. This should show astrogliosis strongly, and also the fibrous astrocytes normally present in white matter. A high concentration of anti-GFAP will stain everything in the CNS, because astrocyte processes are everywhere there.

The traditional astrocyte stain is Cajal's gold-sublimate. This shows normal and gliotic fibrous astrocytes nicely, but it takes time. For protoplasmic astrocytes you need electron microscopy, wich takes even more time. 

John Kiernan
Anatomy, UWO, London, Canada
= = =
On 15/04/15, Stephen KumJew  <stephen.jew <@t> sydney.edu.au> wrote:
> I was wondering if anyone could recommend an antibody (and best dilution) which is more effective than GFAP in staining both resting and active astrocytes in human brain please.
> 
> Thanks
> 
> STEPHEN KUM JEW | Senior Technical Officer
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