Dear Kathy
We're basically dealing with human tissues, but occasionally wander off into
the animal kingdom. A few years ago we've used mo-anti-Ki-67, clone MIB-1
(Coulter-Immunotech), on a (very limited) number of dog tumors with
reasonable success. The concentration of the antibody was 4 ug/ml
(corresponding to 1:50, although Coulter-Immunotech does no longer give the
concentration of their reagent [another case of 'you guys don't need to know
and should buy kits anyway'?]). At that time we used a microwave protocol
for pretreatment (3 x 20 slides in 3 x 220 ml; 8 min. at 850 W, 2 x 5 min.
at 450 W, followed by 15 min in hot buffer) with citrate buffer (10 mM, pH
6.0), which worked good. Since then - and this applies to human tissue -
we've switched to a pressure cooker protocol for pretreatment, using the
same buffer. You may also want to try an alkaline buffer with a microwave
protocol, such as 100 mM Tris, pH 8.5, which works nicely with MIB-1 (on
human tissue).
If your study on mast cell tumors in dogs is purely experimental, you could
also consider BrdU-labeling as an alternative method to determine
proliferation.
Best regards

Andi Kappeler
Institute of Pathology, University of Bern
Murtenstrasse 31
CH-3010 Bern
Phone +41 31 632 32 05  /  Fax +41 31 381 87 64