Comparison of immunofluorescence and immunoperoxidase techniques for detection of tissue antigen

Sensitivity and efficiency of four immunohistochemical methods as defined by staining of artificial sections

Direct (DIF) and indirect (IIF) immunofluorescence, indirect immunoperoxidase conjugate (IPC) and unlabelled antibody peroxidase antiperoxidase (PAP) staining was performed on sections of artificial substrate containing different concentrations of human immunoglobulin (Ig)A or IgG. Detection sensitivity, in terms of the lowest amount of discernible antigen, was evaluated by direct microscopy and by microphotometry. Staining efficiency (signal-to-noise ratio) was evaluated by microphotometry. Only minor differences in antigen detection sensitivity were found when IPC and PAP were compared with DIF and IIF under appropriate conditions. The sensitivity of DIF was only marginally improved by raised conjugate concentration and prolonged incubation time. Microphotometry of DIF on ethanol-fixed IgA substrate revealed that the staining intensity increased proportionally with the antigen concentration whereas on formaldehyde-fixed substrate a progressive masking of the antigen was indicated which, however, could be overcome by applying raised conjugate concentration and prolonged incubation time. Such antigenic self masking was of relatively little importance to IPC and PAP staining, probably because of the inherent amplification in these methods. An additional masking effect due to extraneous protein was revealed by DIF when ethanol-fixed sections had been soaked in bovine serum albumin and postfixed with formaldehyde; unmasking was achieved by proteolytic treatment of the sections.

Quantitation of immunoglobulin- and peptide hormone-producing cells in gastrointestinal mucosa. Comparison of direct immunofluorescence and the unlabelled antibody peroxidase--antiperoxidase method

Direct immunofluorescence (DIF) and the unlabelled antibody peroxidase--antiperoxidase (PAP) methods were compared on a quantitative basis with regard to visualization of IgA immunocytes and gastrin cells in human gastric mucosa, and secretin cells in canine duodenal mucosa. With both DIF and PAP, two serial sections from 13 biopsy specimens were evaluated for each cell type--thus keeping tissue preparation the same with both staining methods. The three cell types were well visualized regardless of method, and there was no significant difference between cell numbers recorded with the DIF or PAP. When blind duplicate counts were obtained with an interval of three weeks, comparisons of weighted differences and the Kendall's rank correlation test indicated good precision; the reproducibility of duplicate enumerations with each method was comparable to that between the two methods. It was concluded that DIF and PAP are equally applicable for studies of these three cell types under the conditions used in this investigation.

A study of astrocytes in retinoblastomas using the immunoperoxidase technique and antibodies to glial fibrillary acidic protein

We identified astrocytes in 12 of 14 randomly selected formalin-fixed Paraplast-embedded retinoblastomas, using the avidin-biotin-peroxidase complex of the immunoperoxidase techniques and antibodies to purified glial fibrillary acidic protein. In two of these eyes, both of which had extensive choroidal invasion by retinoblastoma, we found no tumor cells containing glial fibrillary acidic protein. Astrocytes were observed in metastases within the neurologic tissue of the central nervous system in two cases, but were rarely noted in metastatic foci within the subarachnoid space, and were not found in distant metastases to other sites. These findings suggested that although some astrocytes may become incorporated into retinoblastomas from the retina as the neoplastic cells proliferate and the tumor grows, others proliferate in response to the tumor. Although we found foci of cells containing glial fibrillary acidic protein in some retinoblastomas, convincing evidence of glial differentiation from tumor cells was not observed in any of the retinoblastomas we studied.

Diagnostic procedures in immunodermatology

Most immunologic diseases are caused by the derailment of the humoral or cellular pathways of the immunologic defense system. This derailment results from numerous factors such as the inability of the patient to remove the pathogen; the consumption, defect, or deficiency in any component of these pathways, and the overproduction of any of the components. To diagnose these immunologic disorders one has to detect the pathogen and the reactions caused by it and to determine the cause of its nonclearance. The immunofluorescence techniques has been invaluable in detecting both the antigen that causes the disease and the reactions initiated by the antigen, such as the production of antibodies and the activation of the complement system. The immunoperoxidase technique has also been used for these purposes in certain instances. For detecting the circulating immune complexes which occur as intermediates in the chain of reactions initiated by the antigen, various physiochemical and biologic techniques have been used. However, none of these tests seems to be totally reliable for determining whether circulating immune complexes are present. The consumption of complement was detected by hemolytic estimations and radial immunodiffusion or rocket electrphoresis. These techniques were also useful in detecting the hereditary deficiencies in immunoglobulins and components of classical and alternative pathways of complement activation. Since these techniques cannot be used to estimate IgE, the radioallergosorbent test was used to measure such levels in the atopic patients. Cellular hypersensitivity was detected with skin tests together with methods which assess the ability of lymphocytes to produce mediators in response to antigen. Many of these mediator assays, however, are not suitable for this purpose. A satisfactory substitute appears to be to determine the factor in antigen-stimulated, lymphocyte culture supernatants which activates macrophages to take up radiolabeled colloidal gold or radiolabeled glucosamine. In contact allergic dermatitis, an increase in the IgD-bearing lymphocytes and granulocytes has also been correlated with cellular hypersensitivity. Lymphocytes and polymorphonuclear leukocytes coated with antibodies mainly directed against nuclear antigens of the basal layer cells of the noninvolved epidermis have invariably been encountered in psoriasis. The use of these findings for diagnostic purposes and for understanding the mechanisms of certain diseases is being explored.

Cutaneous immunohistochemistry. The direct immunoperioxidase and immunoglobulin-enzyme bridge methods compared with the immunofluorescence method in dermatology

Two immunohistochemical methods, using the enzyme horseradish peroxidase, the direct immunoperoxidase (DIP) and the immunoglobulin-enzyme bridge (IEB) method were applied on 129 skin specimens of 81 patients with lupus erythematosus, bullous pemphigoid, pemphigus vulgaris and rosacea. These methods were compared with each other and with the immunofluorescence (IF) method. The DIP method was preferred to the IEB method because of the greater contrast between the specific staining and the nonspecific staining of the former. The results obtained with both peroxidase methods were comparable with those of the IF method.