What's new in light and electron microscopic immunocytochemistry? Application of the protein A-gold technique to routinely processed tissue

Applications of immunogold labeling in ultrastructural pathology

This review provides an update on the use of postembedding immunogold labeling, preferentially of the protein A-gold technique, for electron microscopic research in diseased states. In the first part, some helpful antigen recovery techniques for use of immunogold labeling of ultrathin sections prepared from routinely aldehyde (and osmium tetroxide) fixed and conventionally epoxy resin-embedded tissue are cited. In the second part, selected applications for studies of tumor cell surface conjugates, such as polysialic acid in Wilms tumor, proinsulin-insulin conversion in human insulinoma, and the importance of pre-Golgi intermediates for retention of a misfolded polypeptide hormone in a protein misfolding disease, are discussed.

Applications of immunogold and lectin-gold labeling in tumor research and diagnosis

Immunohistochemistry and carbohydrate histochemistry have had an enormous impact on both tumor research and diagnosis. In particular, immunogold labeling has provided significant advantages over classical fluorescence and enzyme-based techniques. In light microscopy, the silver-intensified gold labeling has proven highly sensitive and precise in localization. In electron microscopy, the gold particle marker was a prerequisite for successful and unequivocal antigen detection in electron-dense cellular structures such as secretory granules. In this review we demonstrate the usefulness of light and electron microscopical gold labeling techniques as applied in tumor research and diagnosis. The examples include expression of beta-1,6 branches and specific sialoglycoconjugates in colon carcinoma, b-12 carbohydrate epitope in breast carcinoma, polysialic acid in neuroendocrine tumors of lung, adrenal and thyroid, as well as studies on proinsulin to insulin conversion in insulinomas. In addition, practical hints for prevention of background staining, tissue fixation, and silver intensification of gold labeling are given.

Molecular and phenotypic variability in the congenital alveolar proteinosis syndrome associated with inherited surfactant protein B deficiency

Congenital alveolar proteinosis (CAP) is an often fatal cause of respiratory failure in term newborn infants, which has been associated with a genetic deficiency of surfactant protein B (SP-B) as a result of a frameshift mutation (121ins2) in a family with three affected siblings. In the index cases the deficiency of SP-B was associated with qualitative and quantitative abnormalities of the surfactant proteins A and C. Immunostaining for lung surfactant proteins and a search for the 121ins2 mutation by restriction enzyme analysis of DNA extracted from paraffin-embedded lung tissue was performed for 7 additional affected infants from 6 families, bringing to 10 the total number of patients with CAP who have been studied. In six infants, the surfactant protein immunostaining pattern was similar to that of the index cases. Of these, three patients were homozygous for the 121ins2 mutation; one was a compound heterozygote with the 121ins2 in one allele and a different mutation in the other; and three patients lacked the mutation in both alleles. One infant had an abundance of SP-B, suggesting phenotypic heterogeneity in CAP. Lung ultrastructural abnormalities, such as a reduced number of lamellar bodies, absent tubular myelin, and basal secretion of surfactant lipids and proteins, suggest a significant derangement of surfactant metabolism. The phenotypic heterogeneity in infants with CAP raises the possibility that variable degrees of SP-B deficiency may be more common than previously suspected.

Ultrastructural localization of 2,4-dinitrophenyl groups in mouse epidermis following skin painting with 2,4-dinitrofluorobenzene and 2,4-dinitrothiocyanatebenzene: an immunoelectron microscopical study

The ultrastructural localization of 2,4-dinitrophenyl (DNP) groups in mouse epidermis after epicutaneous application of the contact sensitizer 2,4-dinitrofluorobenzene (DNFB) and the tolerogen 2,4-dinitrothiocyanatebenzene (DNTB) was investigated at varying times using immunoelectron microscopy with the protein A - gold technique. After application of DNFB, there was a homogenous cytoplasmic labeling of all epidermal cells. The intracellular localization of the DNP groups was not restricted to cytoplasmic organelles belonging to the endocytotic - lysosomal system. The numerous endocytotic organelles, Birbeck granules, and lysosomes of the Langerhans cells (LCs) typically observed after application of contact sensitizers also did not show an increased number of gold particles. Skin painting with DNTB resulted in a similar distribution and time-course of immunolabeling, but this compound did not induce cellular and the endocytotic activation of LCs as seen after DNFB application. These results demonstrate that contact sensitizers do not require specific cellular uptake and intracellular processing by the endocytotic - lysosomal compartment of the LCs before membrane presentation. However, a cellular and endocytotic activation of the LCs by haptens may be an important mechanism for T effector cell activation.

Electron microscope localisation of insulin-like immunoreactivity of conventionally processed human insulinomas

Localisation of insulin-like immunoreactivity has been studied using the immunogold staining procedure on thin sections of 6 human insulinomas, conventionally processed for electron microscopy. The labelling was restricted to the secretory granules. Depending on their morphology, these either resembled B-cell granules of human adult pancreas or belonged to the atypical (non-diagnostic) group. Within the former group, those with a crystalloid core or an amorphous dense or moderately dense core were strongly immunoreactive, whereas others, filled with a pale material, were poorly labelled. Most granules of this type were stored together within the heavily granulated cells of 3 insulinomas, presenting the classical features of clinical and biological behaviour and a typical light microscopic staining pattern. In contrast, the non-diagnostic granules, characterized by their smaller size, a very dense core and a thin halo, were mainly found within the poorly granulated cells making up the other tumours, and showed a very uneven labelling. Strongly labelled granules were found in one insulinoma that also belonged to the classical type; these were stored together with a few diagnostic granules within the same cells. Only poorly labelled atypical granules were present in two cases revealing a number of unusual features; these included moderate elevation of insulinaemia, uncertain tumour histology, as well as weak immunostaining for insulin/proinsulin and variable argyrophilia of the tumour in paraffin sections. These findings suggest that human insulinomas differ not only in storage capacity but also in their degree of granule maturation. This may involve some deficiency of either the prohormone conversion or the subsequent processing of the cleavage products.