Hi Timothy,
We are experiencing exactly the same problem with our ISH work. We are 
using a Cambio probe and the Vectastain elite ABC for detection. Most of 
the nuclei  stain bron with the DAB. Neither Cambio nor Vecta can offer 
a solution. I have increased my peroxide incubation, added Tween and BSA 
to all solutions, incubated in Horse serum and/or milk powder but I 
still cannot get rid of the nuclear staining.
I am going on leave today till 6 Jan and would appreciate it if you will 
pass on any suggestions.
Regards

Coskran, Timothy M wrote:

>Hello,
>
>Has anyone ever encountered the following type of IHC background problem:
>With two separate antibodies, one a cytoplasmic marker and the other a
>membrane marker, every single nucleus in the section turns brown.  The stain
>itself works, as most of the time you can read through the background, but
>all test slides and negative controls (omission of primary) are affected.
>
>Both antibodies are rabbit polyclonals, both are steam retrieved one with
>citrate pH 6 the other with EDTA.  Both are detected using a whole IgG
>biotinylated goat anti rabbit secondary followed by Elite ABC and Dako
>Liquid DAB+.  Blocks included 3.0% hydrogen peroxide (aq), Dako Biotin
>Blocking system and Dako Protein block.  All were stained on an IHC stainer.
>
>In addition, both of theses antibodies have been reliable for months (using
>the above protocol steps), until now......
>
>Thanks,
>Tim Coskran
>Pfizer
>
>
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-- 
Dave Lizamore 				(lizamoredj@anatomy.wits.ac.za)
Faculty of Health Sciences		School of Anatomical Sciences
University of the Witwatersrand
Tel +27 (011) 717 2716			Fax: +27 (011) 717 2702