Immunoperoxidase techniques. I. Facts and artifacts

A Dermatopathologist's Guide to Troubleshooting Immunohistochemistry--Part 2: Troubleshooting Immunohistochemical Tests in the Laboratory

Unexpected staining patterns can arise from problems occurring in any of the steps required for IHC, some of which are discussed in part I of this CME series. Whether used to differentiate benign from malignant tumors, identify tumor subtypes, subtypes of hematopoietic malignancies, or identifying targets for therapy, the pathologist must be intimately familiar with the potential pitfalls that are inherent in the IHC methodology to troubleshoot problems in the laboratory, and more importantly, when interpreting immunohistochemical staining, to avoid pitfalls of false-positive or false-negative stains.

Immunohistochemistry as an important tool in biomarkers detection and clinical practice

The immunohistochemistry technique is used in the search for cell or tissue antigens that range from amino acids and proteins to infectious agents and specific cellular populations. The technique comprises two phases: (1) slides preparation and stages involved for the reaction; (2) interpretation and quantification of the obtained expression. Immunohistochemistry is an important tool for scientific research and also a complementary technique for the elucidation of differential diagnoses which are not determinable by conventional analysis with hematoxylin and eosin. In the last couple of decades there has been an exponential increase in publications on immunohistochemistry and immunocytochemistry techniques. This review covers the immunohistochemistry technique; its history, applications, importance, limitations, difficulties, problems and some aspects related to results interpretation and quantification. Future developments on the immunohistochemistry technique and its expression quantification should not be disseminated in two languages—that of the pathologist and another of clinician or surgeon. The scientific, diagnostic and prognostic applications of this methodology must be explored in a bid to benefit of patient. In order to achieve this goal a collaboration and pooling of knowledge from both of these valuable medical areas is vital

Expression of varicella-zoster virus immediate-early regulatory protein IE63 in neurons of latently infected human sensory ganglia

Varicella-zoster virus (VZV) causes varicella and establishes latency in sensory nerve ganglia, but the characteristics of VZV latency are not well defined. Immunohistochemical detection of the VZV immediate-early 63 (IE63) protein in ganglion neurons has been described, but there are significant discrepancies in estimates of the frequency of IE63-positive neurons, varying from a rare event to abundant expression. We examined IE63 expression in cadaver ganglia using a high-potency rabbit anti-IE63 antibody and corresponding preimmune serum. Using standard immunohistochemical techniques, we evaluated 10 ganglia that contained VZV DNA from seven individuals. These experiments showed that neuronal pigments were a confounding variable; however, by examining sections coded to prevent investigator bias and applying statistical analysis, we determined that IE63 protein, if present, is in a very small proportion of neurons (<2.8%). To refine estimates of IE63 protein abundance, we modified our protocol by incorporating a biological stain to exclude the pigment signal and evaluated 27 ganglia from 18 individuals. We identified IE63 protein in neurons within only one ganglion, in which VZV glycoprotein E and an immune cell infiltrate were also demonstrated. Antigen preservation was shown by detection of neuronal synaptophysin. These data provide evidence that the expression of IE63 protein, which has been referred to as a latency-associated protein, is rare. Refining estimates of VZV protein expression in neurons is important for developing a hypothesis about the mechanisms by which VZV latency may be maintained.

Chlamydia pneumoniae in atheroma: consideration of criteria for causality

AIMS

(1) To seek evidence of the existence of Chlamydia pneumoniae in a spectrum of atheromatous lesions in different types of arteries from individuals of different ages, using a polymerase chain reaction (PCR) assay supported by electron microscopy and immunocytochemistry; (2) to use electron microscopy to examine interactions between C pneumoniae and the cells present in the arterial tissue; (3) to assess the extent to which the data fulfil the criteria for causality.

METHODS

At necropsy examination, 35 arterial specimens were taken from 25 subjects. The grade of atheroma was determined macroscopically and microscopically and the tissues coded and examined by the three techniques.

RESULTS

Of the 35 specimens, 24 had macroscopic or microscopic atheromatous lesions of varying degree. Twenty two of the 35 specimens were examined by electron microscopy, C pneumoniae-like bodies being found in 11 (50%); seven specimens were examined by the immunocytochemical method, positive staining being detected in three; and all specimens were examined by the PCR technique, 15 (43%) being PCR positive. Overall, of the 24 specimens with lesions, 17 (71%) were positive by at least one of the three tests, whereas of the 11 specimens without lesions, only one was positive. The positive specimens comprised 10 of 19 aortas, three of six iliac arteries, and one coronary and one pulmonary artery. C pneumoniae was detected in four of six specimens in which there were early changes and in a 20 year old subject. Concerning the 25 subjects, of 17 who had atheromatous arteries, 14 (82%) were C pneumoniae positive and of the eight who had normal arteries, none was positive.

CONCLUSIONS

There is a strong correlation between C pneumoniae and arterial atheromatous lesions. The organism may contribute to the disease process by damaging smooth muscle cells.

Methodological aspects on immunohistochemistry in dermatology with special reference to neuronal markers

In an attempt to optimize the immunohistochemical procedure for visualizing neuronal markers, such as neuropeptides, in the human skin, different alternatives in all steps of the process were compared. We have studied the influence of type of immunohistochemical method, the biopsy technique, including the size of the punch biopsy, anaesthesia, the choice of fixative and the time of fixation, the storage process, the sectioning parameters, incubation procedure, the type of fluorophore-conjugated antibody and its dilution, mounting and storage, and, finally, microscopical examination. The following procedure was found to give the best result: punch biopsies of 3 mm, taken under local anaesthesia using lidocaine injected into the dermis-subcutis at the place of biopsy; fixation by a buffered 10% formalin solution containing 14% of saturated picric acid for 2 h at 4 degrees C; storage in 10% sucrose buffer for at least 24 h up to 1 month at 4 degrees C or deep-frozen to -70 degrees C for 2 months (with only a minor structural deterioration); cryostat sectioning of the biopsies with a section thickness of 14 microns and with the cutting edge perpendicular to the skin surface; rhodamine (TRITC)-conjugated, instead of fluorescein-isothiocyanate (FITC)-conjugated, secondary antiserum, since it gives a lower background fluorescence; and for the incubation and mounting procedures, our standard laboratory routines were applied. The result is an optimal indirect immunofluorescence technique, to be applied in dermatology. We also found that biopsies taken under local anaesthesia with chloroethyl spray lost almost all immunofluorescence for several neuronal markers in the epidermis-upper dermis.

Cytopathology of malignant mesothelioma: a study of its patterns and histological bases

We have reviewed the effusion cytology of 51 cases of histologically proven malignant mesothelioma of the pleura (49 cases) and the peritoneum (2 cases). The patient group included 45 males and 6 females, aged 45-83 yr. A cytological diagnosis of malignancy had been rendered on 43 cases, and in 30 of them it was consistent with, or at least suggestive of, a mesothelioma. Diagnostic clues, especially evident in epithelial and biphasic tumors were hypercellularity and/or morular aggregates of malignant cells showing scalloped borders and nuclei with dense chromatin and evident nucleoli. Cytomegaly with multinucleation was also frequently observed. Reactive mesothelial cells were often present along with other non specific features such as red blood cells, fibrin, necrotic debris. In 13 cases, a diagnosis of malignancy was entertained but mesothelioma, although considered, was not reported out because of scantiness of material. In four cases, adenocarcinoma was erroneously diagnosed for the presence of deceptive cell vacuoles. In eight cases, no diagnostic cells were recovered in repeated effusions. The first diagnosis was a cytologic one in 37 patients, Tissue study was performed on autopsy (35 patients) and surgical material. The latter was the only source of histology in six cases. Immunocytochemical investigation was negative for carcinoembryonic antigen in all but one tested cases (1/21) and positive for human milk fat globulin in about one-half of the epithelial and biphasic tumors. In 18 of 21 cases, positivity for combined high- and low-molecular-weight keratins was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoperoxidase technique modified by counterstain with azure B as a diagnostic aid in evaluating heavily pigmented melanocytic neoplasms

Heavily-pigmented melanocytic neoplasms are difficult to evaluate on routine hematoxylin and eosin stained slides because pigmented melanocytes are difficult to distinguish from the numerous melanophages that are usually seen in the background of these lesions. Immunoperoxidase staining for S100 protein or HMB-45 antibody using diaminobenzidine (DAB) as chromogen, which forms a brown product, does not adequately distinguish melanocytes from melanophages. We modified this technique by replacing hematoxylin as the counterstain with azure B, which stains melanin green-blue. Thus, positive melanocytes appear brown while melanin granules in their cytoplasm are green-blue. However, negative melanophages only stain green-blue. This technique is useful in evaluating heavily pigmented melanocytic lesions such as malignant melanomas, melanosis of regressing malignant melanoma, residual malignant melanoma in areas of granulation tissue with melanophages, blue nevi, pigmented spindle cell variant of Spitz's nevi and combined nevi.

Immunoenzyme techniques in dermatopathology

The advantages and disadvantages of the immunofluorescence and immunoperoxidase techniques and an introductory description of the major variations of the basic immunoperoxidase method are discussed. The ability to identify intermediate filaments, T and B lymphocyte cell markers, S-100 proteins, myelin basic protein, and carcinoembryonic antigen in tissue sections can assist the dermatopathologist in classifying undifferentiated or histologically similar-appearing tumors. A systematic approach to the diagnosis of a majority of these tumors with the use of immunoenzyme staining is provided.

What's new in dermatopathology

This article reviews the recent English language literature on dematopathology, with an emphasis on publications appearing between January 1986 and July 1987. Immunohistochemistry continues to grow in importance as a diagnostic as well as a research technique. The advent of in situ deoxyribonucleic acid hybridization technology has raised diagnostic accuracy to a new level; it has already proved valuable in the diagnosis of certain viral infections. Areas that have received particular attention include phenotypic characteristics of lymphomas and lymphoma-like conditions, congenital melanocytic nevi and malignant melanoma, neuroendocrine carcinoma and other small cell tumors of the skin, sweat gland carcinomas, and eosinophil and its associated diseases, and unusual infectious diseases involving the skin.

Immunohistochemical evidence of heterogeneity in macular corneal dystrophy

We used the avidin-biotin complex immunoperoxidase technique to test the reactivity of the abnormal corneal accumulations with five different monoclonal antibodies that recognize specific determinants on keratan sulfate. Eighty-eight corneas from 67 patients with macular corneal dystrophy were immunolabeled with the antibodies. In 31 corneas the abnormal accumulations did not react with any of the antikeratan sulfate antibodies, but 18 corneas reacted with all of the antibodies. The remaining corneas reacted with various combinations of the antibodies. The data suggest that the accumulations in macular corneal dystrophy are not always identical and that keratan sulfate is present in some cases but not in others. Thus, based on differences in the storage material, macular corneal dystrophy appears to manifest heterogeneity with at least two distinct varieties: keratan sulfate negative (type 1) and keratan sulfate positive (type 2).