An improved method for preparing thick sections for immuno/histochemistry and confocal microscopy and its use to identify rare events.

Detection of rare events within solid tissues by immunocytochemistry is aided by imaging thick sections. Sections of 40--100 microm thickness of paraformaldehyde-fixed solid tissue can be prepared by use of a vibrating microtome and when immunolabelled these sections can be imaged in a confocal microscope. This approach provides excellent preservation of the structure of the sample and imposes minimal antigenic damage. In studies of the invasion of the bovine intestinal epithelium by Salmonella, this method has allowed detection of individual invading bacteria within large samples. The thick vibrating microtome sections were also used for the detection of rare apoptotic cell nuclei identified by TUNEL staining.