Postembedding immunoelectron microscopy using protein A-gold

Immunocytochemical typification of mesothelial cells in effusions: in vivo and in vitro models

We have performed immunocytochemical, immunoelectron microscopy, Western blot, and culture techniques using monoclonal antibodies against cytokeratin, vimentin, and desmin on 17 benign and 20 malignant effusions of pleural and ascitic origin. Triple coexpression of these three antigens was observed in benign reactive mesothelial cells as well as in one case of mesothelioma. All metastatic adenocarcinoma cells were consistently negative to desmin and positive to cytokeratin and vimentin. Present results were helpful to distinguish reactive and malignant mesothelioma from metastatic carcinoma cells in effusions.

Post-embedding tem signal-to-noise ratio of S-100

We assessed the reactivity of purified S-100 antiserum in immuno-electron microscopy by counting the number of gold particles per microns 2 over inner ear tissues embedded in different media. Sections containing predominantly Schwann's cell cytoplasm and nucleus, afferent fiber axoplasm and myelin sheath of chick cochleae were reacted with anti-S-100 IgG, an antibody to a calcium binding protein of neuronal tissues, then labeled with anti-IgG-gold conjugate. This investigation was conducted because previously published procedures, unmodified, did not yield acceptable results. Preparation of all specimens was identical. Only the medium (PolyBed 812, Araldite or Spurr epoxies; and LR White, LR Gold or Lowicryl plastics) was changed. The medium was made the changing variable because antigens available in post-embedding immuno-electron microscopy are decreased by heat, either used and/or released during polymerization of the embedding medium. The results indicate that: (a) none of the embedding media above provided optimal signal-to-noise ratio for all parts of the nerve stained in the same section; (b) aggregation of gold particles over cells was highest in embedding media with high background labeling over areas devoid of tissue (noise); (c) aggregation occurred randomly throughout both cellular and acellular regions; and (d) particles aggregated less and were distributed more evenly in tissues from media yielding good ultrastructural integrity.

Fine-needle aspiration biopsies of metastatic neuroendocrine tumors in liver: use of transmission electron microscopy and protein A gold technique in diagnosis

Five fine-needle aspiration biopsies of liver were studied to evaluate the use of electron microscopy and protein A gold technique in the diagnosis of metastatic neuroendocrine tumors. All five cases had cytologic features suggestive of neuroendocrine tumors and neurosecretory granules on ultrastructural examination. The aspirates were stained by the immunoperoxidase technique and the postembedding protein A gold technique using the antibody to chromogranin A. Three cases were positive for chromogranin A by both immunoperoxidase and protein A gold techniques. Two cases were positive by protein A gold technique and negative by immunoperoxidase technique. Confirmation of neurosecretory granules by immunochemistry is ideal, since ultrastructurally they can be mimicked by other electron-dense inclusions. Advantage of the protein A gold technique is the use of the same material for both ultrastructural evaluation and the protein A gold technique.

Immunogold detection of chromogranin A in the neuroendocrine tumor

Immunogold ultrastructural localization of chromogranin A in secretory granules within tumor cells provides convincing evidence of endocrine or neuroendocrine differentiation. A modified immunogold method (designed for use on osmicated tissue) produced positive labeling of small granules not only in well-differentiated tumors but also in poorly differentiated small cell tumors primary in lung, cervix, and skin; only a proportion of granules in some of the tumor cells were positively labeled. Many non-small cell lung tumors often stain focally positive for chromogranin A at the light microscopy level, and such tumors may also contain sparse, small, dense granules. Because positive labeling could not be demonstrated over small granules in non-small cell lung tumors, the theory that such tumors are neuroendocrine in type may be erroneous.

Use of ultrastructural immunohistochemistry in human pituitary pathology

Recent advances in ultrastructural immunohistochemistry have provided insight into not only the subcellular localization of single antigens but also the colocalization of two distinct antigens in the same cellular constituent. In the field of pituitary pathology, precise identification of cell types, mechanism of processing, and dynamic intracellular transportation of hormones, as well as production of multiple hormones in the same cells of nontumorous and neoplastic adenohypophyses, have been documented by use of these techniques. The present review deals with the use of major methods for ultrastructural immunohistochemistry including pre-, post-, and non-embedding methods, particularly focusing on their application to human pituitary pathology. Problems of tissue processing and a protocol for double labeling technique using the protein A-gold complex are also described.

Primary localized amyloidosis of the lacrimal glands

Primary localized amyloidosis causing bilateral lacrimal enlargement is rare. The pathogenesis of amyloid deposition within the orbit and other body tissues has not been fully elucidated. The authors report the case of a 72-year-old woman who presented with bilateral lacrimal gland enlargement secondary to amyloid infiltration. The chemical nature of the deposit was characterized using light microscopy, immunohistochemistry, and immunoelectron microscopy. The primary (immunocytic) nature of the amyloid was confirmed by immunohistochemistry demonstrating the presence of monoclonal lambda light chains in the amyloid deposits and in the plasma cells. Using immunoelectron microscopy, amyloid deposits were seen containing lambda light chains in macrophages. It has been postulated that the macrophage has a role in amyloid deposition. The authors believe this to be the first published report of immunoelectron microscopy use in orbital amyloidosis, and that this technique has helped further their understanding of the nature and pathogenesis of this condition.

Immunoelectron microscopy of Rosenthal fibers

Seventeen intracerebral gliomas containing Rosenthal fibers (RF) were studied by an immunoperoxidase method for localization of ubiquitin (UB), glial fibrillary acidic protein (GFAP), desmin and vimentin (VIM). The majority of RF showed an immunohistochemically negative core surrounded by a ring of overlapping reactions for UB, GFAP and VIM. Many RF were entirely negative for UB and intermediate filaments (IF). Immunoelectron microscopic localization of UB and GFAP was performed on seven selected tumors. UB was found in all RF and on IF in the proximity of RF. GFAP reaction was localized on astrocytic IF, including those trapped within RF, and within the granular component of some RF. In contrast to the light microscopic studies, neither GFAP- nor UB-negative RF were found on immunoelectron microscopy. VIM reaction on IF and a few RF was demonstrated in one tumor processed at low temperature into Lowicryl; it was much weaker than that for GFAP. Many cells with RF contained lysosome-like inclusions with material displaying electron density similar to adjacent RF; few of these inclusions were reactive for UB. It is concluded that RF formation is associated with ubiquitination of astrocytic IF. GFAP- and VIM-immunoreactive IF and products of their disintegration contribute to RF material. It is also suggested that the lysosomal system of astrocytes partially degrades RF.

Human pituitary somatotroph adenoma and prolactinoma: an ultrastructural and immunoelectron microscopical study

17 cases of pituitary somatotroph adenoma and 38 cases of prolactinoma were studied with electron microscopy and immunoelectron microscopy using protein A-gold complex. 4 adenomas were shown by immunoelectron microscopy to contain simultaneously growth hormone (GH)-producing and prolactin (PRL)-producing cells. 6 cases were classified as densely granulated GH adenomas and 11 as sparsely granulated variant, whereas only 3 adenomas out of 38 prolactinomas were identified as densely granulated adenomas. The present study showed that not all cells with fibrous bodies possessed secretory granules positive for GH, and in some cells with fibrous bodies PRL-producing granules were also detected. Misplaced exocytosis was found frequently in the sparsely granulated prolactinomas. From these findings it may be suggested that fibrous bodies are not a morphological feature characteristic of pituitary somatotroph adenomas.