One workshop I attended on IHC, the director did both antigen retrieval
(citrate buffer method) and a digestion for Factor VIII with her human
tissue protocol.  Might have to try that, do not remember her sequence on
what came first, since I never do either.

I was successful using a Carnoys fixation (without the chloroform added)
on mouse tumor, no antigen retrieval or enzyme digestion was necessary.
but that may not be possible if your tissues are already in paraffin blocks.

Gayle Callis