There have been several papers over the last ten years dealing with this 
subject. The bottom line appears to be that different antibody reactions are 
affected differently; some unaffected, some enhanced, some diminished and 
some abolished.
To be more specific to your question Mike, HMB-45 and S-100 are unaffected 
by bleaching.

Foss AJ et al  Br J Biomed Sci 1995; 52(1): 22-25
Orchard GE, Calonje E  Am J Dermatopathol 1998; 20(4): 357-361)

I am embarking on a study of some cell proliferation markers and bleaching 
and it appears, initially, that PCNA is abolished.
I can concur with Amos on the use of Azure B. It stains the melanin granules 
green-blue contrasting well with the brown DAB.

Kligora CJ et al  Mod Pathol 1999; 12(12): 1143-7

However, I suppose you could use any basic dye in an acidic solution as 
melanin is strongly basophilic.
The other obvious drawback to bleaching is of course, as others have pointed 
out, the problem of floating of the section.
Ronnie Houston
Cytochemistry & Molecular Pathology
Texas Scottish Rite Hospital for Children
Dallas
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