Hi Alex,
About a year ago we had similar problems with PLAP ( placental alkaline
phosphatase). We tried the DAKO antibody that you are having problems
with and found it quite reliable when used at a 1:10 dilution for 20mins
after microwave antigen retrieval.
We also tried the Biomen antibody ( monoclonal clone PL8-F6 )which was
great. It does not require antigen retrieval and gave good results at the
following dilutions:-  1:100  20mins incubation
                       1:2000 overnight incubation
We now use this antibody and (fingers crossed) don't appear to be having
any problems.
Our detection system is Vector Elite and DAB and our staining is carried
out on a Leica Ig stainer.
Please note that our immuno is carried out on Neuropathology specimens
that have generally had less than 24hours fixation.
Hope this is of help.
Now can you help us? We are currently looking to replace our immuno
stainer and would like your opinion on the Optimax II.
Thanks in advance
Sharron Williams
Neuropathology
Frenchay Hosp
Bristol