The post-fixing the slides in formalin is a good suggestion. Also, try cutting them a bit thinner, 3-4 microns if you're using 5. Additionally, if you need to you might test the antibody on control material (validate!) and see if an 80 degree waterbath for longer (1 hour or so?) keeps them on the slide better than the pressure cooker while still keeping the signal at the desired intensity.
Teri Johnson, HT(ASCP)QIHC
Managing Director Histology Facility
Stowers Institute for Medical Research
1000 E. 50th St.
Kansas City, MO 64110
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