Cell identification and localization by double staining for asialo GM1 and von Willebrand factor. Immunohistochemical analysis of a paraffin-embedded section from a Matrigel plug stimulated with bFGF + IL-12 using mouse monoclonal antibody to asialo GM1 and a rabbit anti–von Willebrand factor antiserum. Asialo GM1-positive cells (dark brown) are indicated by arrows; von Willebrand factor positive cells are purple. Original magnification ×40.