Note: take care to keep sections hydrated at all times.  Drying out will lead to non-specific staining.

  1. De-paraffin and rehydrate slides
    1. Incubate 5’ each in xylenes (x2), then 3’ each in 100% EtOH (x2), 95% EtOH (x2) and 70% EtOH (x2)
    2. Put slide rack in PBS while preparing the next step
  2. Antigen retrieval (AR): water bath at 95°C-100°C for 25’ in 10 mM citrate buffer pH 6.0 or Tris-EDTA pH 9.0 (recommended) (10 mM Tris base + 1 mM EDTA and tween 0.05%, pH will be about 9 w/o adjustment).  Pre-heat buffer in water bath.  After 25’, allow slides to cool on benchtop at least 30’ then transfer to PBS 5’.
  3. Incubate sections with Image iT-signal enhancer (Invitrogen #I36933) (cover sections with several drops) for 30’ at RT (reduces background in green channel…prob. not necessary for red channel secondaries).
  4. Block in PBS + 1% BSA and 2% serum from the host of the secondary antibody (goat serum for Alexa-fluor secondaries; use 20 ml per ml)
    1. Segregate tissue sections from each other with a Pap Pen if necessary
    2. Add 100-250 ml of block to each tissue spot (depends on size, of course)
    3. Incubate at RT for 1 hour in a humidified chamber
  5. Bind tissues with primary antibodies
    1. Make up primary antibodies in PBS + 1% BSA at the appropriate dilutions, plan on 100-250 ml per section if using the pap pen.
    2. Dilute CK14 (LabVison, rabbit) to 1:500 and CK8/18 (Vector, mouse) to 1:500 in the PBS + 1% BSA.
    3. Make sure one section is stained with just the antibody diluent as a control.
    4. Incubate overnight at 4°C in a humidified chamber, if desired, use probe clips for sections with larger area and/or only one section per slide