Immunostaining Protocol

Step 3-4:
Permeabilize with 1% Triton X-100 in PBS for 10 minutes at room temperature and rinse well with PBS.

Steps 5-6:
Set up humidified chamber (box with a lid and water-saturated tissue in it; bottom lined with parafilm) and place coverslips as desired (e.g. to use low solution volumes, in the range of 20-40 ul, pipette antibody directly onto parafilm and carefully place coverslip upside down, i.e. with cells facing down, on top of the drop of solution; if you're using solution volumes greater than 50 ul, you can place the coverslip on the parafilm with the cells facing up and pipette the antibody directly onto it).

Before adding antibody, however, block non-specific antibody binding sites by incubating cells for 10 min in blocking buffer (PBS + 0.1% Tween + 1% serum). After this step, incubate cells with primary antibodies diluted in blocking buffer for 35 mins to 1 hour. If you have never used the antibody before, try several dilutions (low of 1:100 to high of 1:1000, for example).

Step 7:
Transfer coverslips to 6-well plates for PBS washes (3 x 10 min). When washes are done, transfer back to humidified chamber for secondary antibody incubation). Incubate coverslips for 35 mins to 1 hour with the appropriate secondary antibodies diluted in blocking buffer, and wash 3 X 10 minutes with PBS. We use fluorophore-conjugated secondary antibodies from Jackson Immunochemicals. Transfer back to the 6-well plate for final PBS washes (3 x 10 min), and then stain with DAPI if desired (1:15,000 dilution in water of a 5 mg/ml stock). A good RNA stain, which fluoresces in the red channel, is Pyronin Y (1:10,000 dilution in water of a 10 mM stock; must stain with DAPI first). Wash well with PBS.

Step 8 :
Mount the cells for immunofluorescence analysis. We commonly use either MOWIOL/Dabco, which hardens, or the liquid mounting media Vectashield (Vector Labs), in which case the coverslips must be sealed with nail varnish). Slides can be stored in the fridge or freezer until analyzed by microscopy.