Hi,
    This is one of the reasons that a negative control is a good idea. If there
is going to be endogenous biotin staining it will show up in the negative
control. I would recommend a dextran polymer secondary like Envision from DAKO
for many of these stains. I did CD 10 on kidney because the basement membrane
and proximal convoluted tubule is supposed to stain, however I noticed it
stained on the negative control as well, along with the distal tubule too
(sites of biotin accumulation). The staining disappeared when I used Envision+.
You could also use biotin block instead, but a negative control can be a life
saver too.
Amos Brooks

"Bennett, Catherine (Katie)" wrote:

> I have never done IHC staining on kidney tissue before and was wondering if
> an avidin/biotin blocking step is needed and/or useful.
>
> *********************************
> Catherine "Katie" Bresee Bennett
> Sr. Research Technologist
> Lovelace Respiratory Research Institute
> Albuquerque, New Mexico