why i can't using the same polyclonal antibody(e.g. flu) in formalin fixed paraffin embedded tissue that it works in frozen section? i have already tried the AR by using pressure cooker with various buffer ( citrate pH 6, EDTA pH 8, target retrieval solution pH9 DAKO). i use 1.5 bar 10 minutes for AR in pressure cooker. it is strange that i use a monoclonal antibody (e.g. H1) for the immunonstaining on the same tissue section, it works perfectly! so i am sure that the AR method is no problem to a certain extent. So, what's the problem is? any other AR method suggested?