Plaque sizes on BHK(TK−), 95-19, and 95-19/BEC cells. (A to C) Photographic images of representative plaques formed by HSV-1(F) on monolayers of BHK(TK−) (A), 95-19 (B), and 95-19/BEC (C) cells immunostained with antibody directed against gD, as described in Materials and Methods. (D) Plaque formed by PRV on 95-19 cells stained with amido black.