I'd second what Tim says, and add that if background is still a problem
     after using casein (non-fat dried milk) you could add either gelatin or PVA
     (both 2%) to your blocking solution.

     I would also like to mention to anyohne doing IF that, in Dallas, we
     switched all our fluorescent secondaries to Alexa dyes (Molecular Probes),
     as we get a much brighter signal,less fading on exposure to UV, and less
     background. In fact we exposed a section with Alexa 594 (the equivalent to
     Texas Red) continuously for 48 hours with very little fading of the
     reaction (unpublished results).

     Ronnie Houston
     Regional Histology Operations Manager
     Bon Secours Health Partners Laboratories
     5801 Bremo Road
     Richmond,VA 23226


______________________________ Reply Separator _________________________________
Subject: RE: Immunohistochemistry
Author:  "Morken, Tim"  at BSHSIBTW
Date:    4/12/02 9:15 AM






       Solutions of  powdered milk have been used (the protein casien
       (sp?)blocks
       non-specific binding)and some companies sell their own
       proprietary
       protein-free blocking agents.

       Tim Morken
       CDC, Atlanta

       -----Original Message-----
       From: Miller, Barbara [mailto:bmiller2@iupui.edu]
       Sent: Friday, April 12, 2002 8:48 AM
       To: 'histonet@pathology.swmed.edu'
       Cc: Miller, Barbara
       Subject: Immunohistochemistry



       Does anyknow of blocking agents other than serum or albumin
       that would
       provide a low background for immunohistochemistry.   We are
       using a
       fluorescent  dye (often Texas Red) and background is a problem so far.

       Thank you for your help.

       Bobbi Miller
       Department of Gastroenterology
       Roudebush Medical Center
       Indianapolis, IN

       e-mail:  bmiller2@iupui.edu