Jackie,

In general, there is NO such thing as 'overfixation' in formaldehyde.
The statement should qualify as an urban myth!
That said, we have tested most clinically applicable antibodies on human
tissues fixed for up to 1 year in phosphate buffered formaldehyde and have
found no significant diminishment of immunoreactivity.
One caveat, the immuno protocol must have been optimized on control tissues
fixed for a similar time to the test material.
In general, this means that any 'antigen retrieval' performed prior to
immunostaining usually has to have a somewhat extended
application time in order to accommodate the more extensive cross-linking
obtained after lengthy fixation.

My advice is to go for it, bearing the above in mind!

You may find the following reference of some use;

Arber DA. Effect of prolonged formalin fixation on the immunohistochemical
reactivity of breast markers.
Appl Immunohistochem Mol Morphol. 2002; 10(2): 183-186.

Regards,

Bryan


----- Original Message -----
From: "Jackie M O'Connor" 
To: 
Sent: Friday, December 03, 2004 10:18 AM
Subject: [Histonet] Overfixed tissues for IHC


> Happy Friday -
> I've been asked if tissues that have been in formalin for 5 months are
> still good for IHC (I don't know what antibodies they want).
> I'd appreciate your feedback on this one, anyone and everyone.
>
> Thanks -
> Jackie O'
> _______________________________________________
> Histonet mailing list
> Histonet@lists.utsouthwestern.edu
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>



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