Fig. 4.

The Cat-315 epitope is extracellular. E16 plus 1 CD (A, B) and E16 plus 7 CD (C, D) cultures were fixed and permeabilized before immunostaining (A,C) or reacted with antibody Cat-315 before fixation (B, D). The cell surface-associated immunoreactivity seen in fixed and permeabilized cultures is retained when cultures are stained without fixation or permeabilization, whereas the intracellular staining is not seen in the unfixed, unpermeabilized cultures. This demonstrates that the surface-associated Cat-315 epitope is extracellular. Scale bars: A–D, 25 μm.