, which will permeabilize some cells--not what you want if you intend to stain for cell-surface antigens. If you are staining for intracellular antigens, how you permeabilize AFTER fixation can also dramatically affect your results. Detergents tend to discriminate against cytoskeletal elements but allow better access of antibodies to the nucleus; post-fixation with -20 methanol (after PFA) allows better retention of cytoskeletal elements but removed lipid-anchored proteins. It's actually pretty complicated-- you can download a detailed protocol and notes from