>I have heard mention about using saponin for cytokine immunohistochemistry
>(ie. Interleukins, etc) on formaldehyde fixed paraffin embedded material.
>Has anyone more information. Is it used in the wash buffer or retrieval
>buffer.
>
>Thanks
>
>Jim Manavis

*******


Saponin is very useful for immunostaining of cytokines in intact cells.
Saponin  creates holes in the outer membrane allowing your antibodies go in
and out. The action of saponin is however reversible. After after washing
with buffer without it, the cells will close again. Therefore, you need to
add saponin to ALL reagents from endogenous peroxidase blocking until the
chromogen solution.
Although there are reports that claim its necessity the use of saponin for
tissue sections is however doubtful. Personally I believe that after
sectioning of a tissue block, all cells in it are cut through, having their
interior completely exposed. From this point of view saponin is not needed.
However, you may just add it as a "soap" for reducing non-specific binding
of your antibodies, like with Tween-20 or Triton-X-100.

Recently, we have completed an investigation to the reliability of IFNgamma
immunohistochemistry and cytochemistry using 13 different commercially
available antibodies. It came out that at least with  anti-IFNgamma on
tissue sections a lot of nonsens has been published!! It is our impression
that this situation is certainly not unique for IFNg...... So please be
careful with cytokine immunohistochemistry  reports!!!!!!!!

Chris