karen

Being Liver tissue, have you thought about endogenous biotin(EB) being the
culprit instead of endogenous peroxidase(EP)? Are the red cells staining
(EP)? or do the cells that  stain look like inclusions(EB)? You could try
either a biotin block prior to your IHC run or use another detection system
such as PAP / APAAP / Glucose oxidase etc. Hope this helps.


Zenobia Haffajee
HAPS, Newcastle, Australia



At 11:03 AM 10/07/00 -0500, you wrote:
>How can you successfully perform immunohistochemistry on slides of liver
>tissue using horse-radish peroxidase and DAB?  How do you quench the
>endogenous peroxidase in the tissue so everything doesn't turn brown?  I've
>tried 3, 10 and 15 % H2O2 in both methanol and di water for 20 min. up to 1
>hour with no success.  The tissues are formalin fixed and embeded in
>paraffin.  We then used a pH 6.0 citrate buffer/microwave antigen retrieval
>system for our primary Ab detection.  Even with all that the endogenous
>enzyme caused the false positive with the DAB.  Anyone have any
>suggestions?
>Thank you for all replies.
>Karen in Omaha
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