Fixation-dependent vimentin immunoreactivity of mono- and polyclonal antibodies in brain tissue of cattle, rabbits, rats and mice.

The immunohistochemical staining of vimentin in paraffin-embedded sections from adult cattle, rabbit, rat and mouse brain fixed in different fixatives (formaldehyde, methacarn, ethanol) was examined using two monoclonal antibodies and a polyclonal antiserum. In non-trypsinized formaldehyde-fixed tissue sections both monoclonal antibodies and the polyclonal antibodies failed to stain vimentin. Following trypsinization of formaldehyde-fixed sections of the four species the meninges, endothelial cells of blood vessels, ependymal cells and the stroma of the choroid plexus were labelled by the monoclonal and polyclonal antibodies used. Astrocytes and Bergmann glial fibers in pretrypsinized formaldehyde-fixed sections from cattle, rabbit and rat brain, however, showed only weak staining. Fixation of cattle and rat brain in methacarn markedly improved the vimentin immunoreactivity of astrocytes and Bergmann glial fibers. The best fixative for the preservation of immunoreactive determinants of vimentin in astrocytes and Bergmann glial fibers in cattle, rabbit and rat brain was ethanol. In brain tissue from mice both monoclonal antibodies labelled only mesoderm-derived tissue components, but did not recognize vimentin in astrocytes and Bergmann glial fibers. Pre-heating formaldehyde-fixed sections from cattle, rabbit and rat brain in a microwave oven prior to the immunohistochemical reaction resulted in an enormous enhancement of vimentin staining of mesoderm-derived tissues, of astrocytes and bergmann cell fibers.