Mark, 
This is a new one to me. We, in fact, use new and recycled Shandon's Histosolve
in our processor and de-paraffininzation steps. Although there are a multitude
of procedural steps that may cause weak or no staining in IHC, in my mere five
years of doing IHC, to my knowlege xylene substitutes have never been a
contributing factor. 
Best Regards, 
Rachel Stock, HTL(ASCP)

Organogenesis, Inc. 
150 Dan Road
Canton, MA 02021

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Has anyone heard or read anything with regard to poor antigenicity when
tissues are cleared using Xylene substitutes during processing or staining? 
Someone told me that they were told not to use xylene substitutes of any kind
for tissue processing or for the deparaffinization  and clearing steps in the
staining process because it would effect immuno staining negatively. They did
not have details as to how, what or why.  Please enlighten me if you know
anything with regard to this.

Thank You,
Mark Lewis