Kris,

   Apart from the remarks already made I would like to add the following:

   FFPE  slides  are strictly pre-fixed (first fixed as a block, then cut
   and  stained)  and  cryostat sections from a fresh frozen tissue block
   are  post-fixed  (first  cut,  then fixed and stained). We have seen a
   great  difference  between  post-fixation and pre-fixation with IHC of
   small  proteins  like  cytokines.  It appeared that the cytokine leaks
   away   in   the  fixative  in  the  post-fixation  situation,  whereas
   pre-fixation  works fine. I will send the paper we wrote as attachment
   to  your private mail. This year a better overview on this matter will
   be published in Biotechnic & Histochem.

   Chris van der Loos, PhD
   Dept. of Pathology
   Academic Medical Center M2-230
   Meibergdreef 9
   NL-1105 AZ Amsterdam
   The Netherlands


   Date: Tue, 6 Mar 2007 13:22:05 -0500
   From: "Kalleberg, Kristopher" 
   Subject: [Histonet] paraffin vs. frozen
   To: 
   If  anyone  could  give  some  insight  as to what the differences are
   between
   frozen sections and paraffin sections when performing IHC I would
   greatly appreciate it.  I am running a study and the results for a few
   of  the  markers  I am not to happy with and am contemplating changing
   over
   to frozen sections for upcoming studies.  Is there any rhyme or reason
   as to why antibodies work better with frozens sections or paraffin
   sections?  Any help will of course be greatly appreciated.

   Kris Kalleberg
   Research Scientist
   Unilever R&D
   40 Merritt Blvd.
   Trumbull, CT 06611
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