Dear Mateo,
I have been struggling for the same problem with double staining using a 
rabbit anti-Ki67 and mouse antibody. A couple of weeks ago the problem was 
solved. Our NeoMarkers (Lab Vision Corp.) rep came in with a new rabbit 
monoclonal (you read this right) anti-Ki67. Clone SP6, product number 
RM-9106-R2. I tested the stuff and found out this antibody works fine 
indeed, maybe even better as the old Dako rabbit anti-Ki56!

Chris van der Loos
Academic Medical Center
Dept. of Cardiovascular Pathology
Amsterdam, The Netherlands

Mateo Ziu wrote:
 >Date: 25 Feb 2003 17:00:35 -0600
 >From: Mateo Ziu 
 >Subject: Ki67 for Human Cells in Mouse tissue
 >
 >Hello everybody,
 >
 >I have been srugling these past weeks with my Ki-67 staining.
 >
 >I have a cells from a Brain Tumor Human cell line which I injected in the
 >brain of mouse. I have Frozen Section of this animals.
 >
 >I would like to know if anybody has a good protocol for the Ki-67 staining
 >(Biotinylated. Using DAB staining). What antibody, first and second do you
 >use.
 >
 >Before I used the Rabbit Anti-Human of DAKO. It worked perfectly. 
Unfortunatly
 >DAKO doesn't produce it anymore (Ah, these For - Profit Companies!!!).
 >
 >I have tried with my old protocol many other Antibodies of different
 >Companies, but nothing!!
 >
 >Please if anybody has a protocol that works in Frosen sections for Ki67, I
 >would appreciate the help.
 >
 >Mateo Ziu
 >
 >Neurosurgery Lab
 >Brigham and Women's Hospital
 >LMRC Bldg, Rm 121
 >Boston, MA 02115 (USA)