To avoid confusion about two fixatives for doing T and B cell surface 
markers (CD markers, lymphocytes).

ZincTris, or as PharMingen calls it, zinc fixative.  This is a NON FORMALIN
fixation, and you CANNOT quench endogenous peroxidase.  For some reason, 
this nonformalin fixative tends to fix the peroxidase in cells big time,
and it cannot be cleared with hydrogen peroxide blockers.  Both publications
which used this fixative used alkaline phosphatase substrate kits. It is 
important to remember, this fixative was developed for use on T and B cell
markers (lymphocytes, CD markers in humans (1) and rodents (2).  

Zinc FORMALIN, as far as I know, can have endogenous peroxidase blocked in
tissues.  I have never used this for IHC, so can't vouch for times, blockers,
etc used successfully.  You can use peroxidase AND alk phos substrate kits
with this formalin based fixative aka zinc formol.  

I think this is a USER BEWARE  situation, and if you are beginning to
use the zinc TRIS aka zinc fixative, please specify very carefully that it is
the nonformalin variety and vice versa for zinc formalin when you discuss the 
fixation used.  This will be a huge help to IHC afficiandos and beginners.

Gayle Callis