Immunofluorescence analysis of gB-2 endocytosis mutants in transiently transfected COS7 cells. For cell surface staining (E to H), cells were fixed with paraformaldehyde; for intracellular staining (A to D), they were fixed with paraformaldehyde and then permeabilized with Triton X-100. Cells were stained with polyclonal antibody R91, followed by a goat anti-rabbit IgG-FITC conjugate. Magnification, ×400. Panels: A and E, wild-type gB-2; B and F, Y827A; C and G, LL849/850AA; D and H, Y867A.