Routine Formaldehyde Fixation Irreversibly Reduces Immunoreactivity of Bcl-2 in the Nuclear Compartment of Breast Cancer Cells, but not in the Cytoplasm:

Walking a thin line between fixation and epitope binding - characterization of antigen retrieval methods suitable for eosinophil and HSV-2 staining in formalin-fixed female reproductive tissue

Antibody-based fluorescence analysis of female reproductive tissues in research of sexually transmitted diseases allows for an in-depth understanding of protein localization, interactions, and pathogenesis. However, in many cases, cryosectioning is not compatible with biosafety regulations; at all times, exposure of lab personnel and the public to potentially harmful pathogens from biological infectious material must be avoided; thus, formaldehyde fixation is essential. Due to formaldehyde's cross-linking properties, protein detection with antibodies can be impeded. To allow effective epitope binding during immunofluorescence of formalin-fixed paraffin-embedded vaginal tissue, we investigated two antigen retrieval methods. We tested these methods regarding their suitability for automated image analysis, facilitating reproducible quantitative microscopic data acquisition in sexually transmitted disease research. Heat-based retrieval at 80°C in citrate buffer proved to increase antibody binding to eosinophil protein and HSV-2 visibly and tissue morphology best, and was the most efficient for sample processing and quantitative analysis.

Optimized Protocol of Methanol Treatment for Immunofluorescent Staining in Fixed Brain Slices

We optimized methanol treatment in paraformaldehyde-fixed slices for immunofluorescent staining of ependymal basal bodies in brain ventricles. As 100% methanol induced severe deformations to the slices (including rolling and folding over), we tried to decrease methanol concentration. We found that 33.3% to 75% methanol could result in ideal immunostaining of basal bodies without inducing obvious deformations. Instead of treating slices at -20°C (without proper cryoprotection measurements) as suggested in previous studies, we carried out methanol treatment at room temperature. Our modified protocol can not only raise immunostaining efficiency in tissue slices, it may also prevent potential freezing damages to the samples.

When tissue antigens and antibodies get along: revisiting the technical aspects of immunohistochemistry--the red, brown, and blue technique

Once focused mainly on the characterization of neoplasms, immunohistochemistry (IHC) today is used in the investigation of a broad range of disease processes with applications in diagnosis, prognostication, therapeutic decisions to tailor treatment to an individual patient, and investigations into the pathogenesis of disease. This review addresses the technical aspects of immunohistochemistry (and, to a lesser extent, immunocytochemistry) with attention to the antigen-antibody reaction, optimal fixation techniques, tissue processing considerations, antigen retrieval methods, detection systems, selection and use of an autostainer, standardization and validation of IHC tests, preparation of proper tissue and reagent controls, tissue microarrays and other high-throughput systems, quality assurance/quality control measures, interpretation of the IHC reaction, and reporting of results. It is now more important than ever, with these sophisticated applications, to standardize the entire IHC process from tissue collection through interpretation and reporting to minimize variability among laboratories and to facilitate quantification and interlaboratory comparison of IHC results.

Technical aspects of immunohistochemistry

Immunohistochemistry is an integral technique in many veterinary laboratories for diagnostic and research purposes. In the last decade, the ability to detect antigens (Ags) in tissue sections has improved dramatically, mainly by countering the deleterious effects of formaldehyde with antigen retrieval (AR) and increasing sensitivity of the detection systems. In this review, I address these topics and provide an overview of technical aspects of immunohistochemistry, including those related to antibodies (Abs) and Ags, fixation, AR, detection methods, background, and troubleshooting. Microarray technology and the use of rabbit monoclonal Abs in immunohistochemistry are also discussed.

Immuno-localization of Fas and FasL in rat hepatic endothelial cells: influence of different fixation protocols

Immunocytochemistry has been widely used to localize molecules involved in apoptosis. In this short report, we describe with the aid of confocal laser scanning microscopy the immunolocalization of Fas and FasL on liver sinusoidal endothelial cells, and show how the localization of these two molecules differ when the cells are fixed with different fixation protocols. Methanol fixation shows diffuse staining of Fas and FasL in the cytoplasm, as well as in the nucleus. In contrast, paraformaldehyde fixation reveals the presence of Fas and FasL polarized at one side of the cell and only in the cytoplasm. After fixation with a combination of paraformaldehyde and glutaraldehyde the polarization is still present although the fluorescence is concentrated and located as bright dots in the cytoplasm. In conclusion, paraformaldehyde preserves the (nuclear) membrane-associated structures better then methanol and results in a more accurate localization of Fas and FasL. Understanding the different outcome of these common used fixation protocols will assist investigators to select the most suitable method for visualizing membrane-bound Fas and FasL.