Re-evaluation of epoxy resin sections for light and electron microscopic immunostaining

Epoxy resins provide optimal tissue morphology at both the light and the el ectron microscopic level and therefore enable correlative studies on semith in and thin sections from the same tissue block. Here we report on an appro ach to retain these advantages for immunolabeling studies by adapting and c ombining well-known techniques, i.e., surface etching with sodium ethoxide and heat-mediated antigen retrieval. We propose a simple procedure for immu nostaining semithin and thin epoxy resin sections. To check its applicabili ty, well characterized, commercially available antibodies (against E-cadher in, alpha -catenin, and beta -catenin) were used on sections of human small intestine. By light microscopy, the immunostaining efficiency was compared on cryo-, paraffin, and epoxy semithin sections processed in parallel. The most detailed results were obtained on semithin sections, where the labeli ng precisely delineated the lateral plasma membrane of the enterocytes. At the electron microscopic level the procedure did not damage the structures and allowed an efficient, reproducible immunogold labeling extending homoge neously over exceptionally wide tissue areas. The three antibodies specific ally labeled the zonula adherens of the junctional complex between epitheli al cells and, in agreement with light microscopic observations, the lateral plasma membrane.