Ross,

it is always dangerous to generalize especially because we use ihc to stain for a wide variety of cellular and tissue antigens and something is always likely to be the exception however I'm going to risk it.

 

The rule of thumb is to try to prevent overheating of tissues during exposure to processing chemicals. There are certainly proponents of low metling point paraffins but we have a very successful immunohistochemistry laboratory that routinely utilizes a 58 degrees metling point paraffin. I do not recommend that you change paraffin to resolve your quality issues as I personally don't believe that this is likely to make the difference. Lastly I would add that in my opinion, if your tissues are well fixed, most if not all antigens will survive exposure to 60 degrees. Its interesting to note that we frequently expose tissues to very high heat (90-100 degrees C) to achieve epitope retrieval which seems to contradict this notion that temperatures must be kept as low as possible.

 

 

 

 

 

Vinnie Della Speranza
Manager for Anatomic Pathology Services
Medical University of South Carolina
165 Ashley Avenue  Suite 309
Charleston, SC 29425
Ph: 843-792-6353
fax: 843-792-8974

>>> Ross Stapf <rstapf@adventisthealthcare.com> 10/16/02 04:04PM >>>
Hi everyone:

I was reading through Diagnostic Immunohistochemistry by Dabbs and came across a comment that paraffin temperatures should not exceed 56 degrees when doing immuno's on the tissue later.

We have been trying to standardize our methods for optimal immuno results.  We have the occasional case where the staining is not as expected.  We are trying to eliminate as many of these problems as possible.  Is the paraffin temp really that important?  I am beginning to wonder if this is one of the reasons for those cases that should, but just don't stain positive.

  We have been using Paraplast and Paraplast xtra for over 10 years at 60 degrees.  If I do experiment with a paraffin with a lower melting point, what can I expect?  Will my techs have a harder time cutting the blocks?  Will I need to increase my infiltration times?

Turn around time is very important, I don't want techs complaining that they can't get good routine sections just to possibly fix an immuno variable.  Also from my research so far the lower melting point paraffin is more expensive.

Basically has anybody made a change in paraffin for this reason, and was it worth it?

Ross Stapf
Histology Supervisor
Washington Adventist Hospital
Takoma Park MD