Large Block Embedding and “Pop-OfF” Technique for Immunoelectron Microscopy

A technique for immunoelectron microscopy is described whereby tissue is embedded in large (6 × 12 mm) plastic blocks and reembedded (“popped off”) directly from semithin (3-μm) sections for thin sectioning. This technique is particularly useful in locating relatively sparse cells or tissue structures. Three acrylic plastics were evaluated: Lowicryl K4M, LR Gold, and LR White. Results indicated excellent ultrastructural morphologic preservation and retention of antigenicity with the first two plastics both comparable to conventional methods of processing. Lowicryl and LR Gold were successfully adapted to the large block pop-off technique. Technical problems were encountered with LR White.