When doing immunogold IHC, increasing the salt concentration was
another way to help reduce the ionic interactions, also fish gelatin,
and BSA, the high priced variety.  I know some people like additional
salt added to their buffers for nonimmunogold IHC.   A good discussion
of this in terms of immunogold work, is in the BBI catalog, from Vector,
and the BBI handout for doing IG-IHC gives recommended salt conc in
buffers.

Gayle Callis