Comparison of the immunolabeling of heated and deplasticized epoxy sections on the electron microscopical level.

The purpose of this study was to compare the yield of immunogold labeling of heated epoxy sections with the yield of labeling of deplasticized epoxy sections, and to compare the immunolabeling of deplasticized high-accelerator epoxy sections and deplasticized low-accelerator epoxy sections. Renal swine tissue and human thyroid tissue were embedded in both high- and low-accelerator epoxy resin and also in LR-White resin. Immunogold labeling was performed on deplasticized (ethoxide-treated), heated and non-treated ultrathin sections from these specimens. The renal tissue was immunolabeled with anti-IgG, and the thyroid tissue was immunolabeled with anti-thyroglobulin. The ethoxide treatment of the epoxy sections induced complete deplasticizing. The immunogold labeling with anti-IgG on deplasticized epoxy sections of renal tissue demonstrated significantly more intense immunolabeling of immune complex deposits than the corresponding epoxy sections which were exposed to heat in citrate buffer. The results for labeling areas of thyroglobulin substance with anti-thyroglobulin showed no significant differences between deplasticized and heated epoxy sections, probably because the sodium ethoxide partly destroys the antigenicity. Deplasticized high-accelerator epoxy sections showed significantly higher yield of immunolabeling than deplasticized low-accelerator epoxy sections and LR-White sections both for anti-IgG and anti-thyroglobulin. This can be explained by the reduced tendency for the knife to cleave proteins when cutting high-accelerator epoxy sections. High-accelerator epoxy sections which were exposed to heat in citrate buffer were more intensely immunolabeled than similarly treated low-accelerator epoxy sections, in agreement with previous results. The ultrastructural preservation of the tissues of deplasticized epoxy sections was inferior compared with the other sections. This study shows that the choice between deplasticizing technique or heating of epoxy sections has to be considered with respect to the nature of the antigen and to the requirement for ultrastructural preservation.