Loss of different surface antigens during permeabilization. Cells were labeled following a classical immunofluorescence procedure (upper panel) or a two-step procedure (lower panel). In both cases, cells were permeabilized with methanol at −20°C. The antibodies used detected csA-SA (A, B), H36 (C, D), p25 (E, F), p23 (G, H) or p80 (I, J). The effect of cell permeabilization on surface labeling differed for the various antigens considered. Scale bar: 5 μm.