The purpose of this study was to examine how the intensity of the immunogold labeling on epoxy sections was affected by the use of
propylene oxide as an agent in addition to
ethanol in the
dehydration and infiltration, and also to examine the effect on the immunogold labeling by adding small amounts of
propylene oxide to the embedding mixture. Increased knowledge of the mechanism for
antigen detection on resin sections was another aim. Thyroid tissue, kidney tissue, and
fibrin were embedded in
epoxy resin; some with
ethanol as the only
dehydration agent and others with
propylene oxide as an additional agent in
dehydration, infiltration or embedding steps in different ways. Immunogold labeling was performed with
anti-thyroglobulin,
anti-IgG, and anti-
fibrinogen, respectively. A higher degree of immunogold labeling was achieved by increasing the concentration of accelerator during infiltration and embedding (Brorson and Skjørten, 1996a, Micron, 27, 211-217). The immunogold labeling of the sections that were based on additional
dehydration and infiltration with
propylene oxide showed significantly more intense labeling than the sections of tissues that had only been exposed to
ethanol in the
dehydration and infiltration steps. The embedding of tissues in a mixture of
epoxy resin and 5-10%
propylene oxide gave higher yields of immunogold labeling than if pure
epoxy resin was used for the embedding. The improved labeling is explained by higher amplitudes of protruding
antigens on the surface of the sections because
antigens are less tightly incorporated in the
polymer network when using
propylene oxide as additional agent in
dehydration, infiltration or embedding. These results illustrate the advantage of using
propylene oxide as an additional agent when preparing specimens for immunoelectron microscopy with
epoxy resin embedding.