Patricia,
            I have also been following the saponin
story with respect to cytokine staining. All the
protocols I've seen differ in other respects but
all use .1% saponin. One article I read used
saponin for cytokines but omitted it for T-cell
staining. I am doing a run as we speak w/
saponin and have used .1-.2% saponin I'm not
sure but I don't think .1% is critical.
    As far as I understand it saponin is used for
cytokines and not cell surface marker, What
are you looking for?
    Background could be one of many things:
Block (serum from same species as secondary
is made in.) Secondary try diluting it out, for
cytokine they use 1:500 in some articles.
Incomplete Quenching of peroxidase. Hope this
helps.
Lastly I use saponin in everything up to and
including ABC(vector elite).

Jamie Erickson
Genetics Institute