The development of immunohistochemistry

The cell theory and cellular pathology: Discovery, refinements and applications fundamental to advances in biology and medicine

This review explores the developments leading up to the establishment of the cell theory and cellular pathology and their subsequent refinements and applications while focusing on the individuals who have made seminal advances in the field. The links between cell biology, cell pathology and cell injury research are emphasized. Recognition also is given to the importance of technological advances in microscopy, histology, biochemical and molecular methods for discovery in cell biology and cell pathology. Particular attention is focused on the work of Rudolph Virchow and his former students in the formulation of the cell theory in biology and pathology and John F. R. Kerr and colleagues who identified and developed a comprehensive characterization of apoptosis, thereby giving impetus to the contemporary field of cell injury research. Cell injury research remains an important and fruitful field of ongoing inquiry and discovery.

The road from cytotoxins to immunohistochemistry

This review article traces the immunohistochemistry ancestry of cytotoxins as antibodies. The immunohistochemistry success, as a diagnostic and research test, stood on the shoulders of negative and positive experimentation results with cytotoxins from the first half of the twentieth century. This is when experimental immunologists came with the understanding of the need for both antigen and antibody purification to achieve specificity of the immunological reaction. Simultaneously, protocols were developed, which involved injecting antigenic material into experimental animals. During this time, reliable methods for evaluation of antiserum strength or titer were established. The evolution of antigen preparation for immunofluorescence is presented here as one of the transitional steps to modern immunohistochemistry. This work paved the way for the development of the monoclonal and polyclonal antibodies methodology. The article is written from the author's perspective as an experimental immunologist and a hands-on participant during many steps of development in modern morphological laboratory diagnostics. Knowledge of the roots of immunohistochemistry is useful for laboratory professionals in appreciation of predecessors' contributions. Familiarity with history of experimental immunology would be beneficial for understanding the methodological principles of their current work as well as future development prospects.

In situ protein detection with enhanced specificity using DNA-conjugated antibodies and proximity ligation

Antibodies are important tools in anatomical pathology and research, but the quality of in situ protein detection by immunohistochemistry greatly depends on the choice of antibodies and the abundance of the targeted proteins. Many antibodies used in scientific research do not meet requirements for specificity and sensitivity. Accordingly, methods that improve antibody performance and produce quantitative data can greatly advance both scientific investigations and clinical diagnostics based on protein expression and in situ localization. We demonstrate here protocols for antibody labeling that allow specific protein detection in tissues via bright-field in situ proximity ligation assays, where each protein molecule must be recognized by two antibodies. We further demonstrate that single polyclonal antibodies or purified serum preparations can be used for these dual recognition assays. The requirement for protein recognition by pairs of antibody conjugates can significantly improve specificity of protein detection over single-binder assays.

Immunohistochemical Analysis of Urothelial Carcinoma Tissues for Proliferation and Differentiation Markers

Immunohistochemistry is a standard method in histopathology and enables the localized detection of proteins in histological tissue sections. Specific antibodies are bound to cellular antigens, captured by secondary antibodies or polymers, linked to enzymes and visualized by chromogenic substrates. Here, we describe an automated staining technique for larger slide batches as well as a manual protocol for only few slides using a polymer technique. We focus on differentiation markers, measures of cell proliferation, and therapeutic targets in benign and malignant urothelial tissues.

Strategies for immunohistochemical protein localization using antibodies: What did we learn from neurotransmitter transporters in glial cells and neurons

Immunocytochemistry and Western blotting are still major methods for protein localization, but they rely on the specificity of the antibodies. Validation of antibody specificity remains challenging mostly because ideal negative controls are often unavailable. Further, immunochemical labeling patterns are also influenced by a number of other factors such as postmortem changes, fixation procedures and blocking agents as well as the general assay conditions (e.g., buffers, temperature, etc.). Western blotting similarly depends on tissue collection and sample preparation as well as the electrophoretic separation, transfer to blotting membranes and the immunochemical probing of immobilized molecules. Publication of inaccurate information on protein distribution has downstream consequences for other researchers because the interpretation of physiological and pharmacological observations depends on information on where ion channels, receptors, enzymes or transporters are located. Despite numerous reports, some of which are strongly worded, erroneous localization data are being published. Here we describe the extent of the problem and illustrate the nature of the pitfalls with examples from studies of neurotransmitter transporters. We explain the importance of supplementing immunochemical observations with other measurements (e.g., mRNA levels and distribution, protein activity, mass spectrometry, electrophysiological recordings, etc.) and why quantitative considerations are integral parts of the quality control. Further, we propose a practical strategy for researchers who plan to embark on a localization study. We also share our thoughts about guidelines for quality control. GLIA 2016;64:2045-2064.

Genetically encoded molecular probes to visualize and perturb signaling dynamics in living biological systems

In this Commentary, we discuss two sets of genetically encoded molecular tools that have significantly enhanced our ability to observe and manipulate complex biochemical processes in their native context and that have been essential in deepening our molecular understanding of how intracellular signaling networks function. In particular, genetically encoded biosensors are widely used to directly visualize signaling events in living cells, and we highlight several examples of basic biosensor designs that have enabled researchers to capture the spatial and temporal dynamics of numerous signaling molecules, including second messengers and signaling enzymes, with remarkable detail. Similarly, we discuss a number of genetically encoded biochemical perturbation techniques that are being used to manipulate the activity of various signaling molecules with far greater spatial and temporal selectivity than can be achieved using standard pharmacological or genetic techniques, focusing specifically on examples of chemically driven and light-inducible perturbation strategies. We then describe recent efforts to combine these diverse and powerful molecular tools into a unified platform that can be used to elucidate the molecular details of biological processes that may potentially extend well beyond the realm of signal transduction.

Current status of diagnostic and prognostic markers in melanoma

Melanoma is the most life-threatening common form of skin cancer. While most cutaneous melanomas are cured by surgical resection, a minority will relapse locally, regionally, or distantly. Biomarkers have represented a focal point for research aimed at improving diagnostic accuracy as well as providing prognostic information that may help to guide therapeutic decisions. While systemic melanoma therapies were of extremely limited utility for patients with advanced disease in the past, two drugs have been approved the FDA within the past several years, and it is possible that they may provide even greater impact if employed earlier in the disease process. To optimally employ these therapies, prognostic biomarkers may offer significant value. This article reviews methodologies for both discovery and routine testing of melanoma biomarkers. It also focuses on specific commonly used markers, as well as approaches to studying their applications to specific clinical settings. As the armamentarium of melanoma drugs grows, it is hoped that specific biomarkers will aid in guiding the use of these agents for patients in the clinic.

Genomic analysis at the single-cell level

Studying complex biological systems such as a developing embryo, a tumor, or a microbial ecosystem often involves understanding the behavior and heterogeneity of the individual cells that constitute the system and their interactions. In this review, we discuss a variety of approaches to single-cell genomic analysis.

Effects of propionyl-L-carnitine on ischemia-reperfusion injury in hamster cheek pouch microcirculation

Background and purpose Propionyl-l-carnitine (pLc) exerts protective effects in different experimental models of ischemia–reperfusion (I/R). The aim of the present study was to assess the effects of intravenously and topically applied pLc on microvascular permeability increase induced by I/R in the hamster cheek pouch preparation. Methods The hamster cheek pouch microcirculation was visualized by fluorescence microscopy. Microvascular permeability, leukocyte adhesion to venular walls, perfused capillary length, and capillary red blood cell velocity (V_RBC) were evaluated by computer-assisted methods. E-selectin expression was assessed by in vitro analysis. Lipid peroxidation and reactive oxygen species (ROS) formation were determined by thiobarbituric acid-reactive substances (TBARS) and 2′-7′-dichlorofluorescein (DCF), respectively. Results In control animals, I/R caused a significant increase in permeability and in the leukocyte adhesion in venules. Capillary perfusion and V_RBC decreased. TBARS levels and DCF fluorescence significantly increased compared with baseline. Intravenously infused pLc dose-dependently prevented leakage and leukocyte adhesion, preserved capillary perfusion, and induced vasodilation at the end of reperfusion, while ROS concentration decreased. Inhibition of nitric oxide synthase prior to pLc caused vasoconstriction and partially blunted the pLc-induced protective effects; inhibition of the endothelium-derived hyperpolarizing factor (EDHF) abolished pLc effects. Topical application of pLc on cheek pouch membrane produced the same effects as observed with intravenous administration. pLc decreased the E-selectin expression. Conclusions pLc prevents microvascular changes induced by I/R injury. The reduction of permeability increase could be mainly due to EDHF release induce vasodilatation together with NO. The reduction of E-selectin expression prevents leukocyte adhesion and permeability increase.

Embryogenesis of the serotonergic system in the earthwormEisenia fetida (Annelida, Oligochaeta): Immunohistochemical and biochemical studies

Organization of the serotonergic system and changes of the serotonin (5-HT) content were studied during the embryogenesis of the earthworm Eisenia fetida, using immunocytochemistry and HPLC. A gradual emergence of 5-HT immunoreactive (IR) cells and their axon projections in the several ganglia of the central (CNS) and peripheral nervous system are described in the context of a staged time-scale of development. The first 5-HT-IR neurons appear in the subesophageal ganglion at an early embryonic stage (E2), followed by neurons in some rostrally located ventral ganglia. In the cerebral ganglion, 5-HT-IR cells can be detected only from stage E5. The number of labeled cells in each ganglion of the embryo increases until hatching, when it is still considerably lower than that observed in adults. This shows that the development of the 5-HTergic system is far from complete by the end of embryogenesis. Organization of 5-HT-IR innervation of the body wall starts by stages E3 to E4. In the stomatogastric nervous system the first 5-HT-IR fibers can be detected by stage E5. By stage E9 5-HT immunopositive neurons can be observed in both the stomatogastric ganglia and the enteric plexus. Both 5-HT levels and the numbers of the labeled cells show a significant increase before hatching, which indicate a functional maturation of the 5-HTergic system. Based on the early appearance of 5-HT, we suppose that it may play a regulatory role in both the gangliogenesis and the maturation of peripheral functions necessary during postembryonic life.

Calbindin distribution in male, female and lactating rat pituitary

Calcium binding proteins such as calbindin and calretinin have been studied in the pituitary gland, but information on them is still incomplete. To investigate the localization, distribution and role of calbindin in the pituitary, several antibodies to calbindin and to other pituitary markers, such as calretinin and tyrosine-hydroxylase, have been used in male, female and lactating rats. Calbindin has not been localised to a specific endocrine cell population unlike calretinin in the thyrotrophs. There was occasional localization in somatotrophs, thyrotrophs and luteotrophs, but not in corticotrophs or lactotrophs. However, there are sex differences in the expression of this protein as the number of calbindin-immunoreactive cells is higher in the male than in the female pituitary. Furthermore, the number of calbindin containing cells, not lactotrophs, increases in lactating rats and decreases after removal of the pups. It is concluded that calbindin expression may be altered by physiological and endocrine events such lactation, even though it is still unclear why the protein is not related to a specific cell type. The simultaneous use of monoclonal and polyclonal antisera to calbindin revealed that the rabbit antibody recognizes nuclear and cytoplasmic calbindin, while the monoclonal one binds only to the cytoplasmic calbindin. The suggestion is that calbindin may have a secondary role that is not simply to bind calcium.

Freeze-substitution: origins and applications

Freeze-substitution is a physicochemical process in which biological specimens are immobilized and stabilized for microscopy. Water frozen within cells is replaced by organic solvents at subzero temperatures. Freeze-substitution is widely used for ultrastructural and immunocytochemical analyses of cells by transmission and scanning electron microscopy. Less well recognized is its superiority over conventional chemical fixation in preserving labile and rare tissue antigens for immunocytochemistry by light microscopy. In the postgenome era, the focus of molecular genetics will shift from analyzing DNA sequence structure to elucidating the function of gene networks, the intercellular effects of polygenetic diseases, and the conformational rearrangements of proteins in situ. Novel strategies will be needed to integrate knowledge of chemical structures of normal and abnormal macromolecules with the physiology and developmental biology of cells and tissues from whole organisms. This review summarizes the progress and future prospects of freeze-substitution for such explorations.

The increasing power of immunohistochemistry and immunocytochemistry

Since its introduction in the early 1940s, immunostaining technology has developed in a remarkable way, and the applicability of immunohisto/cytochemical probing methods will unquestionably continue to increase in several directions. Immunofluorescence remains the most powerful and reliable immunohistochemical approach for multicolour staining to evaluate co-localization of two or more antigens in an objective manner. Moreover, the fluorescent colour signals exhibit a relatively consistent relationship to the actual antigen concentration in the test preparation and are hence better suited for quantitative computerized image analysis than light-microscopic observations of immunoenzyme staining. On the other hand, immunoenzyme methods are more economical with regard to reagent consumption and are therefore ideal for the use in semiautomatic staining machines. In addition, the superior morphological correlate provided by the latter methods, makes them more attractive and adequate for most purposes in diagnostic pathology laboratories. However, multicolour immunoenzyme staining provides an easily obtainable and reliable result only when the antigens are known a priori to be separately located, both because of technical problems and because imbalanced colour mixing is difficult to evaluate in the light microscope. All these aspects of immunohistochemistry are briefly reviewed in this historical perspective coloured by the author's own experience.

Microscopic imaging of cells

The microworld was revealed to investigators through a glass bead or a hanging water droplet long before optics was understood. The cellular structure of plants was well resolved by such simple magnifying glasses, van Leeuwenhoek, the Dutch merchant and amateur microscopist, was the first to report to the English Royal Society his observations of bacteria with his single-lens microscope in 1665.

Improved fixation for immunofluorescence microscopy using light-activated 1,3,5-triazido-2,4,6-trinitrobenzene (TTB)

A new fixation method has been developed for immunofluorescent microscopy using the photosensitive compound 1,3,5-triazido-2,4,6-trinitrobenzene (TTB). Our results show that TTB-fixed cells are well preserved morphologically and that the cellular antigens are better preserved than conventionally fixed cells. By altering one condition at a time in the TTB fixation procedure and analyzing resulting fluorescent antitubulin staining patterns in mammalian tissue culture cells, an optimal procedure was developed. Cells fixed with TTB and stained with antitubulin, antiprekeratin, anti-intermediate filament, anti-alpha-actinin, anti-myosin, antiactin, or anticlathrin were compared with cells fixed by conventional methods and stained with the same antibody. The quality of immunofluorescence images of TTB fixed cells was the same as or better than that of conventionally fixed cells. The most dramatic improvement in image quality was seen when using antiprekeratin or antitubulin. In dividing cells, particularly in metaphase, fluorescent staining with antiactin and anti-alpha-actinin was relatively excluded from the spindle. Antimyosin, on the other hand, stained the spindle and surrounding area more heavily than the subcortical region. We suggest that after TTB fixation, the immunofluorescent patterns of these contractile proteins more closely reflect their relative concentrations in living cells. The exact mechanism for fixation by TTB is not yet known. However, our studies indicated that TTB fixation was not caused by the typical fast photoinduced nitrene diradical mechanism, but rather by some slower, temperature-dependent reaction of a photoactivation product of TTB with the cell.