IMMUNOFLUORESCENT STAINING: THE FLUORESCENT ANTIBODY METHOD

Studying histone inheritance in different systems using imaging-based methods and perspectives

Understanding cell identity is critically important in the fields of cell and developmental biology. During cell division, a mother cell duplicates the genetic material and cellular components to give rise to two daughter cells. While both cells receive the same genetic information, they can take on similar or different cell fates, resulting from a symmetric or asymmetric division. These fates can be modulated by epigenetic mechanisms that can alter gene expression without changing genetic information. Histone proteins, which wrap DNA into fundamental units of chromatin, are major carriers of epigenetic information and can directly influence gene expression and other cellular functions through their interactions with DNA. While it has been well studied how the genetic information is duplicated and segregated, how epigenetic information, such as histones, are inherited through cell division is still an area of investigation. Since canonical histone proteins are incorporated into chromatin during DNA replication and can be modified over time, it is important to study their inheritance within the context of the cell cycle. Here, we outline the biological basis of histone inheritance as well as the imaging-based experimental design that can be used to study this process. Furthermore, we discuss various studies that have investigated this phenomenon with the focus on asymmetrically dividing cells in different systems. This synopsis provides insight into histone inheritance within the context of the cell cycle, along with the technical methods and considerations that must be taken when studying this process in vivo.

Electronic Immunoassay Using Enzymatic Metallization on Microparticles

We present here an inexpensive method for generating a sensitive direct electronic readout in bead-based immunoassays without the use of any intermediate optical instrumentation (e.g., lasers, photomultipliers, etc.). Analyte binding to capture antigen-coated beads or microparticles is converted to probe-directed enzymatically amplified silver metallization on microparticle surfaces. Individual microparticles are then rapidly characterized in a high-throughput manner via single-bead multifrequency electrical impedance spectra captured using a simple and inexpensive microfluidic impedance spectrometry system we develop here, where they flow through a three-dimensional (3D)-printed plastic microaperture sandwiched between plated through-hole electrodes on a printed circuit board. Metallized microparticles are found to have unique impedance signatures distinguishing them from unmetallized ones. Coupled with a machine learning algorithm, this enables a simple electronic readout of the silver metallization density on microparticle surfaces and hence the underlying analyte binding. Here, we also demonstrate the use of this scheme to measure the antibody response to the viral nucleocapsid protein in convalescent COVID-19 patient serum.

Assessing changes in the expression levels of cell surface proteins with a turn-on fluorescent molecular probe

Tri-nitrilotriacetic acid (NTA)-based fluorescent probes were developed and used to image His-tagged-labelled outer membrane protein C (His-OmpC) in live Escherichia coli. One of these probes was designed to light up upon binding, which provided the means to assess changes in the His-OmpC expression levels by taking a simple fluorescence spectrum.

Subcellular Localization of Histidine Phosphorylated Proteins Through Indirect Immunofluorescence

Immunofluorescence (IF) takes advantage of biological and physical mechanisms to identify proteins in cell or tissue samples, exploiting the specificity of antibodies and stimulated fluorescence light emission. Here, we describe an immunofluorescence staining method for the identification of histidine phosphorylated proteins that uses neutral/alkaline conditions and targeted reagents to overcome the chemical lability of histidine phosphorylation. This method describes how 1- and 3-phosphohistidine (pHis) monoclonal antibodies can be used to reveal the localization of proteins containing these elusive phosphoramidate bonds in cells. Standard procedures and materials for IF staining with adherent and nonadherent cells are described.

Beyond the H&E: Advanced Technologies for in situ Tissue Biomarker Imaging

For decades, histopathology with routine hematoxylin and eosin staining has been and remains the gold standard for reaching a morphologic diagnosis in tissue samples from humans and veterinary species. However, within the past decade, there has been exponential growth in advanced techniques for in situ tissue biomarker imaging that bridge the divide between anatomic and molecular pathology. It is now possible to simultaneously observe localization and expression magnitude of multiple protein, nucleic acid, and molecular targets in tissue sections and apply machine learning to synthesize vast, image-derived datasets. As these technologies become more sophisticated and widely available, a team-science approach involving subspecialists with medical, engineering, and physics backgrounds is critical to upholding quality and validity in studies generating these data. The purpose of this manuscript is to detail the scientific premise, tools and training, quality control, and data collection and analysis considerations needed for the most prominent advanced imaging technologies currently applied in tissue sections: immunofluorescence, in situ hybridization, laser capture microdissection, matrix-assisted laser desorption ionization imaging mass spectrometry, and spectroscopic/optical methods. We conclude with a brief overview of future directions for ex vivo and in vivo imaging techniques.

Determination of Protein Expression Level in Cultured Cells by Immunocytochemistry on Paraffin-embedded Cell Blocks

Immunofluorescent staining is currently the method of choice for determination of protein expression levels in cell-culture systems when morphological information is also necessary. The protocol of immunocytochemical staining on paraffin-embedded cell blocks, presented herein, is an excellent alternative to immunofluorescent staining on non-paraffin-embedded fixed cells. In this protocol, a paraffin cell block from HeLa cells was prepared using the thromboplastin-plasma method, and immunocytochemistry was performed for the evaluation of two proliferation markers, CKAP2 and Ki-67. The nuclei and cytoplasmic morphology of the HeLa cells were well preserved in the cell-block slides. At the same time, the CKAP2 and Ki-67 staining patterns in the immunocytochemistry were quite similar to those in immunohistochemical staining in paraffin cancer tissues. With modified cell-culture conditions, including pre-incubation of HeLa cells under serum-free conditions, the effect could be evaluated while preserving architectural information. In conclusion, immunocytochemistry on paraffin-embedded cell blocks is an excellent alternative to immunofluorescent staining.

Altered DNA repair; an early pathogenic pathway in Alzheimer's disease and obesity

Unrepaired DNA double-strand breaks (DSBs) are lethal. The present study compared the extent of DSBs, neuronal apoptosis, and status of two major DSB repair pathways - homologous combinational repair (HR) and nonhomologous end-joining (NHEJ) - in hippocampus of 5–6 month and 16–18 month-old wild-type and APP/PSEN1 mice fed control diet or high fat diet (60% fat from lard). We performed immunohistochemical staining and quantification for nuclear foci formation of γ-H2AX for DSBs, RAD51, and 53BP1, which represent the functional status of HR and NHEJ, respectively. Increased γ-H2AX and caspase-3 staining indicated greater DSBs and associated neuronal apoptosis in APP/PSEN1 mice at both ages studied. RAD51-positive foci were fewer in APP/PSEN1 indicating that HR processes may be diminished in these mice, although NHEJ (53BP1 staining) appeared unchanged. High fat diet in young wild-type mice led to similar changes to those observed in APP/PSEN1 mice (γ-H2AX and caspase-3 staining, and fewer RAD51-positive foci). Overall, these data suggest that APP/PSEN1- and high fat diet-associated early accumulation of DSBs and neuronal cell death, resulted at least in part, from inhibition of HR, one of the major DSB repair pathways.

Flexible direct-growth CNT biosensors

A biosensor was fabricated by growing carbon nanotubes (CNTs) directly on a polyimide flexible substrate at low temperatures (≤400 °C). A biocompatible polymer (poly(para-xylylene), parylene) was subsequently coated on the surface without CNTs as an insulator for future applications of flexible biosensors in in vivo sensing. The feasibility of the CNT flexible biosensor was demonstrated by quantitatively detecting human serum albumin (HSA). The CNT surface was modified with functional groups using UV-ozone, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), and treated with N-hydroxysuccinimide (NHS) to improve the biocompatibility for the conjugation of protein. In addition, anti-HSA (AHSA) was used to capture HSA specifically, and bovine serum albumin (BSA) was applied to block the non-specific sites. The electrical properties of the biosensors applied with various HSA concentrations were measured and quantified using an electrochemical impedance spectroscopy system under AC conditions. The detection limit of the biosensor for HSA detection was approximately 3×10(-11) mg/ml. The proposed sensor has considerable potential for future application in wearable biosensors and implant detection.

IDENTIFICATION OF MYCOPLASMATACEAE BY THE FLUORESCENT ANTIBODY METHOD

Clark, Harold W. (The George Washington University, Washington, D.C.), Jack S. Bailey, Richard C. Fowler, and Thomas McP. Brown. Identification of Mycoplasmataceae by the fluorescent antibody method. J. Bacteriol. 85:111-118. 1963.-The conditions of the fluorescent antibody reactions were studied in relation to their application to Mycoplasmataceae or pleuropneumonia-like organisms (PPLO). Mycoplasma hominis type 1 and 2 antigens and their homologous antisera were used to determine the activity and specificity of these and other strains. Fluorescein isothiocyanate conjugated antiserum globulin preparations were used in both the direct and indirect fluorescent antibody methods. A direct tube technique was used for the detection and measurement of growth in broth cultures by the addition of conjugated antiserum. The specific fluorescent staining and recognition of hot water fixed M. hominis colonies was presented as a suitable identification standard. The antigenic activity was found to remain in the insoluble residue after exposure of M. hominis strains to sonic vibration (9 kc) for 30 min and centrifugation. Brief 2-min exposures of tissue cells to vibration (9 kc) caused the disruption of tissues, with the release of viable and "bound" nonwashable strains that reacted specifically with fluorescent antibody. It is proposed to apply both the sonic vibration and the fluorescent antibody techniques for the identification of Mycoplasmataceae in human tissues.

Labeling procedures employing crystalline fluorescein isothiocyanate

Griffin, Charles W. (Baltimore Biological Laboratory, Baltimore, Md.), Theodore R. Carski, and George S. Warner. Labeling procedures employing crystalline fluorescein isothiocyanate. J. Bacteriol. 82:534-537. 1961.-The effect of altering the ratio of dye to protein in the labeling of three immune globulins with crystalline fluorescein isothiocyanate was the purpose of the study. Direct staining of group A streptococci and rabies-infected mouse brain, and indirect staining of Treponema pallidum (Nichols strain) comprised the three immunological systems selected for investigation. Maximal specific staining and minimal nonspecific background staining were demonstrated by the use of low dye-to-protein labeling ratios.

A RAPID IMMUNOFLUORESCENCE TECHNIQUE FOR DETECTING SALMONELLAE IN RAW MEAT

A rapid 18 hr. technique has been developed for detecting salmonella contaminated carcass and boneless meats. It is based on 43° C. selenite enrichment of samples, followed by immunofluorescent detection of salmonella cells in the enrichment. In tests with 286 meat samples the rapid and conventional techniques agreed in the detection of 93 positive and 149 negative samples. The two tests failed to agree for the remaining 44 samples. The rapid technique thus lacks precision, but could be used as a rapid ‘presumptive’ salmonella test, so that contaminated material could be prevented from reaching the processing lines of food factories.

We thank Dr Betty Hobbs of the Food Hygiene Laboratory for kindly sup plying the meat samples used in this investigation, Dr Patricia Bradstreet of the Standards Laboratory for Serological Reagents for the salmonella diagnostic antisera and Mr R. Kenworthy for performing the goat injections.

Immunoglobulin clases IgG, IgM, IgA and complement component C3 in dental periapical lesions of patients with rheumatoid disease

To identify the immunoglobulin classes present in dental periapical lesions and to determine how, if at all, the distribution of immunoglobulin classes IgG. IgM and IgA differ in the dental periapical lesions of rheumatoid and control patients, paraffin-embedded and frozen tissues from the dental periapical lesions of 36 rheumatoid and 22 control patients were examined by the direct immunofluorescence technique. In addition, both rheumatoid and control tissues were examined for the presence of complement component C3, albumin and fibrinogen. Neither the greater frequency and abundancy with which IgG and to a lesser degree, IgA occurred in the dental periapical lesions of rheumatoid patients than in the corresponding lesions of control patients, nor the more frequent occurrence of complement component C3 in these same lesions, was statistically significant. No difference in the distribution of the various immunoglobulin classed could be discerned between the rheumatoid and control group. Albumin was distributed almost equally between the two patient groups. The greater abundance of fibrinogen among control patients was, however, statistically significant. These results do not provide evidence that an immunologic reaction takes place in the dental periapical lesions of patients with rheumatoid disease similar to that which characterizes rheumatoid inflammation. However, the presence of such a reaction cannot be excluded without more extensive investigation.

Reduction of nonspecific background staining in the fluorescent treponemal antibody-absorption test

The nonspecific background fluorescence which occurs with the fluorescent treponemal antibody-absorption test for syphilis was found to result from a reaction between serum-treated Treponema pallidum organisms and the conjugated antihuman gamma-globulin. It was also shown that beta-lipoprotein and albumin were the important contributing factors in human serum. Various dilutions of 2.5% trypsin in phosphate-buffered saline specifically reduced background fluorescence under proper test conditions. By employing a trypsin digestion method, a semiautomated procedure utilizing a visual readout has been postulated as feasible.

Studies on passive haemolysis mediated by antiserum globulin antibodies

The concurrent action of complement and antiserum globulin (anti-SG) antibodies on red cells coated with an antigen and sensitized with the specific antibodies was studied. The occurrence of haemolysis in such systems is dependent on the haemolytic properties of the anti-SG antibodies used in the test. The haemolytic properties of the immunoglobulins that sensitize the coated cells have no apparent role in the development of the lysis.

The method of titration of antibodies by passive haemolysis can be rendered more sensitive and can be applied to detect antibodies that do not fix complement, if a suitable anti-SG serum is permitted to react with the immunoglobulins that have combined with the antigen coating the erythrocytes. Under standard conditions reproducible titrations can be performed to detect 0·009 μg N Ab/ml with an error equal to 10 per cent.

Persistent infection of cells in culture by measles virus. I. Development and characteristics of HeLa sublines persistently infected with complete virus

Rustigian, Robert (Tufts University School of Medicine, Boston, Mass.). Persistent infection of cells in culture by measles virus. I. Development and characteristics of HeLa sublines persistently infected with complete virus. J. Bacteriol. 92:1792-1804. 1966.-After the development of marked cytopathic effects in HeLa cultures infected with the Edmonston strain of measles virus, renewed cell growth occurred, and HeLa sublines persistently infected with measles virus were obtained. Persistent infection has occurred in a large fraction of the cells of infected clonal lines for more than 300 to 500 cell generations during a period of 6 years. One mechanism by means of which infection was maintained in the clonal lines is transmission of virus or viral subunits from cell to cell at division. Continued subculture of the persistently infected populations resulted in the virtual disappearance of cytopathic effects, a marked decrease in the amount of extracellular virus, and alterations in the cytopathogenicity of virus recovered from persistently infected populations. The intracellular virus-host cell events in late passages of the infected clonal lines appeared to be similar to those in cells of primary infected cultures at early stages of infection, as judged by the pattern of viral immunofluorescence and the very low incidence of cells with intranuclear inclusion bodies. Cultures of the persistently infected clonal lines were highly resistant to super infection by parent Edmonston virus. Cultures of one of these clonal lines were just as susceptible as normal HeLa cultures to vaccinia, herpes simplex, and polio type 2 viruses, and a simian agent, with a possible low degree of resistance to the simian agent.

An immunohistochemical study on renal biopsies in children

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Immunofluorescence study of wild rabies virus and antibody

A concentrate of wild rabies antibody was prepared from hyperimmune serums of three dogs refractory to wild rabies. The animals resisted repeated intramuscular injections of large doses of wild rabies virus in emulsions of whole brain, in emulsions of submaxillary salivary glands, and in emulsified mixtures of brain and submaxillary glands taken from naturally rabid dogs. The antibody was conjugated with fluorochrome and then absorbed by a procedure that gave "cell-free" working solutions of fluorescent antibody. The procedure entailed parallel absorption steps with minced pathological canine submaxillary glands from (1) naturally rabid dogs (these glands contained specific, undegraded, natural antigens of live wild rabies virus plus nonspecific substances and antigens) and (2) nonrabid dogs from a rabies endemic region (these glands contained nonspecific substances and antigens). Extracts from submaxillary glands of the three naturally rabid dogs and one nonrabid dog were stained with a cell-free solution of the fluorescent antibody. The glands of the rabid dogs contained fluorescent aggregates of intense green spherical and filamentous particles. When nonfluorescent canine hyperimmune serum was incubated with rabies-containing submaxillary extract, the rabies antigens were quenched. When nonfluorescent equine fixed virus antiserum was incubated with such extracts, the aggregates still retained bright fluorescence.

Experimental thyroiditis in the rhesus monkey. I. Cytotoxic, mixed-agglutinating and complement-fixing antibodies

Rhesus monkeys inoculated repeatedly with a crude extract of pooled rhesus thyroids plus complete Freund adjuvant produced autoantibodies cytotoxic for monkey and human thyroid cells in vitro. No cytotoxicity was observed with normal rhesus kidney or adrenal cells taken as controls from the same animals. The specific cytotoxic reaction was absorbed by thyroid microsomes, but not by other tissue fractions. Monkey (as well as human) thyroiditis sera failed to fix complement with thyroglobulin although both fixed complement with crude thyroid suspensions. The cytotoxic antibody was heat stable (56°C for 30 min) and required complement for damage to tissue cells. Fractionation by sucrose gradient ultracentrifugation demonstrated that the cytotoxic antibody had a sedimentation rate of about 7S and was stable to sulphydryl agents, whereas the complement-fixing antibody sedimented more rapidly and was largely inactivated by mercaptoethanol treatment. Thus in this case, cytotoxic antibody is not identical with the over-all complement-fixing activity of an antiserum. The presence of organ specific antigen on the surface of cultured rhesus thyroid cells was detected by the mixed agglutination antiglobulin reaction using monkey antisera. The curves of antibody production detected by mixed agglutination and cytotoxicity tend to correspond although the former test was 10–100 times more sensitive.

Immunological studies on Behçet's syndrome

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Clinical Application of Immunofluorescence I. Grouping β-Hemolytic Streptococci

Smith, Thomas B. (Armed Forces Institute of Pathology, Washington, D.C.). Clinical application of immunofluorescence. I. Grouping β-hemolytic streptococci. J. Bacteriol. 89: 198–204. 1965.—Procedures are described for the production of antistreptococcal serum in rabbits and for the preparation of group-specific conjugates for Lancefield groups A, C, and G. A modification of the conventional technique of absorption and inhibition to prevent cross-reactions with common antigens was used with excellent results. In addition, a promising new approach to eliminating cross-reactions of group A conjugate with antigens of groups C and G by dilution with group A-variant antiserum was tested. A complete method is introduced that enables the clinical laboratory to report whether group A streptococci are present in a given throat culture well within 24 hr after the physician collects the sample.