Monoclonal antibodies and the FACS: complementary tools for immunobiology and medicine

Progress in the development and use of monoclonal antibodies to study the evolution and function of the immune systems in the extant lineages of ungulates

Details on the origin and function of the immune system are beginning to emerge from genomic studies tracing the origin of B and T cells and the major histocompatibility complex. This is being accomplished through identification of DNA sequences of ancestral genes present in the genomes of lineages of vertebrates that have evolved from a common primordial ancestor. Information on the evolution of the composition and function of the immune system is being obtained through development of monoclonal antibodies (mAbs) specific for the MHC class I and II molecules and differentially expressed on leukocytes differentiation molecules (LDM). The mAbs have provided the tools needed to compare the similarities and differences in the phenotype and function of immune systems that have evolved during speciation. The majority of information currently available on evolution of the composition and function of the immune system is derived from study of the immune systems in humans and mice. As described in the present review, further information is beginning to emerge from comparative studies of the immune systems in the extant lineages of species present in the two orders of ungulates, Perissodactyla and Artiodactyla. Methods have been developed to facilitate comparative research across species on pathogens affecting animal and human health.

Advances in Mass Spectrometry-Based Single Cell Analysis

Technological developments and improvements in single-cell isolation and analytical platforms allow for advanced molecular profiling at the single-cell level, which reveals cell-to-cell variation within the admixture cells in complex biological or clinical systems. This helps to understand the cellular heterogeneity of normal or diseased tissues and organs. However, most studies focused on the analysis of nucleic acids (e.g., DNA and RNA) and mass spectrometry (MS)-based analysis for proteins and metabolites of a single cell lagged until recently. Undoubtedly, MS-based single-cell analysis will provide a deeper insight into cellular mechanisms related to health and disease. This review summarizes recent advances in MS-based single-cell analysis methods and their applications in biology and medicine.

Detergent micelle conjugates containing amino acid monomers allow purification of human IgG near neutral pH

Industrial scale production of therapeutic monoclonal antibodies (mAbs) is commonly achieved with Protein A chromatography, a process that requires exposure of the antibody to strongly acidic conditions during the eluting step. Exposure to acid inactivates virus contaminants but may, in parallel, lead to antibody aggregation that must be eliminated or kept at acceptably low levels. This report seeks to provide a practical method for overcoming a long-standing problem. We show how Brij-O20 detergent micelles, conjugated by the amphiphilic [(bathophenanthroline)₃:Fe²⁺] complex in the presence of amino acid monomers: phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp), isoleucine (Ile) or valine (Val), efficiently capture polyclonal human IgG (hIgG) at neutral pH and allow its recovery by extraction either at pH 4 (85-97% yield) or at pH 6.3 (72-84% yield). Of the five amino acid monomers surveyed, Phe or Tyr produced the highest overall process yield at both pH 4 and 6.3. The monomeric state of the purified hIgG's was confirmed by dynamic light scattering (DLS). Potential advantages of the purification method are discussed.

Methods to Produce Monoclonal Antibodies for the Prevention and Treatment of Viral Infections

A viral threat can arise suddenly and quickly turn into a major epidemic or pandemic. In such a case, it is necessary to develop effective means of therapy and prevention in a short time. Vaccine development takes decades, and the use of antiviral compounds is often ineffective and unsafe. A quick response may be the use of convalescent plasma, but a number of difficulties associated with it forced researchers to switch to the development of safer and more effective drugs based on monoclonal antibodies (mAbs). In order to provide protection, such drugs must have a key characteristic-neutralizing properties, i.e., the ability to block viral infection. Currently, there are several approaches to produce mAbs in the researchers' toolkit, however, none of them may serve as a gold standard. Each approach has its own advantages and disadvantages. The choice of the method depends both on the characteristics of the virus and on time constraints and technical challenges. This review provides a comparative analysis of modern methods to produce neutralizing mAbs and describes current trends in the design of antibodies for therapy and prevention of viral diseases.

Dual-layered hydrogels allow complete genome recovery with nucleic acid cytometry

Targeting specific cells for sequencing is important for applications in cancer, microbiology, and infectious disease. Nucleic acid cytometry is a powerful approach for accomplishing this because it allows specific cells to be isolated based on sequence biomarkers that are otherwise impossible to detect. However, existing methods require specialized microfluidic devices, limiting adoption. Here, we describe a modified workflow that uses particle-templated emulsification and flow cytometry to conduct the essential steps of cell detection and sorting normally accomplished by microfluidics. Our microfluidic-free workflow allows facile isolation and sequencing of cells, viruses, and nucleic acids and thus provides a powerful enrichment approach for targeted sequencing applications. This article is protected by copyright. All rights reserved.

Analysis of the Cellular Immune Responses to Vaccines

Flow cytometry, enzyme-linked immunospot (ELISpot), and cellular cytotoxicity assays are powerful tools for studying the cellular immune response toward intracellular pathogens and vaccines in livestock species. Lymphocytes from immunized animals can be purified using Ficoll-Paque density gradient centrifugation and evaluated for their antigen specificity or reactivity toward a vaccine. Here, we describe staining of bovine lymphocytes with peptide (p)-MHC class I tetramers and antibodies specific toward cellular activation markers for evaluation by multiparametric flow cytometry, as well as interferon (IFN)-γ ELISpot and cytotoxicity using chromium (⁵¹Cr) release assays. A small component on the use of immunoinformatics for fine-tuning the identification of a minimal CTL epitope is included, and a newly developed and simple assay to measure TCR avidity.

Early dynamic changes in circulating tumor cells and prognostic relevance following interventional radiological treatments in patients with hepatocellular carcinoma

The aim of this study was to investigate the dynamic changes of circulating tumor cells (CTCs) in patients with hepatocellular carcinoma (HCC) before and immediately after conducting a microwave ablation (MWA) and conventional transarterial chemoembolization (C-TACE). Additionally, the CTCs short-term dynamics were compared with the clinical course of the HCC-patients. Blood samples from 17 patients with HCC who underwent MWA (n = 10) or C-TACE (n = 7) were analyzed. Venous blood was taken before and immediately after the radiological interventions to isolate and quantify CTCs using flow cytometry. CTCs were identified as CD45- and positive for the markers ASGPR, CD146 and CD274 (PD-L1). Patients were followed of up to 2.2 years after the radiological intervention. CTCs were detected in 13 HCC patients (76%) prior to the radiological interventions. The rate of CTCs was significantly decreased after the intervention in patients treated with MWA (0.4 CTCs/mL of blood, p = 0.031). However, no significant differences were observed in patients who received C-TACE (0.3 CTCs/mL of blood, p = 0.300). Overall, no correlation was found between the CTCs rate before and after the radiological intervention and recurrence rate of HCC. This preliminary data could confirm the tumoricidal effects of MWA in patients with HCC by significantly decreasing CTCs rate. In our study, we were able to detect CTCs in HCC patients using 3 different tumor markers. This preliminary data shows significant lower CTCs detected in response to MWA. However, large-scale randomized clinical trials are needed to determine the future role and the prognostic relevance of CTCs following this treatment.

Approaches to overcome flow cytometry limitations in the analysis of cells from veterinary relevant species

Background

Flow cytometry is a powerful tool for the multiparameter analysis of leukocyte subsets on the single cell level. Recent advances have greatly increased the number of fluorochrome-labeled antibodies in flow cytometry. In particular, an increase in available fluorochromes with distinct excitation and emission spectra combined with novel multicolor flow cytometers with several lasers have enhanced the generation of multidimensional expression data for leukocytes and other cell types. However, these advances have mainly benefited the analysis of human or mouse cell samples given the lack of reagents for most animal species. The flow cytometric analysis of important veterinary, agricultural, wildlife, and other animal species is still hampered by several technical limitations, even though animal species other than the mouse can serve as more accurate models of specific human physiology and diseases.

Results

Here we present time-tested approaches that our laboratory regularly uses in the multiparameter flow cytometric analysis of ovine leukocytes. The discussed approaches will be applicable to the analysis of cells from most animal species and include direct modification of antibodies by covalent conjugation or Fc-directed labeling (Zenon™ technology), labeled secondary antibodies and other second step reagents, labeled receptor ligands, and antibodies with species cross-reactivity.

Conclusions

Using refined technical approaches, the number of parameters analyzed by flow cytometry per cell sample can be greatly increased, enabling multidimensional analysis of rare samples and giving critical insight into veterinary and other less commonly analyzed species. By maximizing information from each cell sample, multicolor flow cytometry can reduce the required number of animals used in a study.

Classification of the Immune Composition in the Tumor Infiltrate

Flow cytometry is one of the most suitable techniques for analyzing and classifying different cell suspensions derived from blood or others compartments. The characterization of all different cellular subtypes is made with different antibodies that detect surface or intracytoplasmic antigens. Here we describe the technique to thoroughly characterize immune cells from tumor infiltrates and proceed to isolation using single-cell sorting.

A Quartz Crystal Microbalance Immunosensor for Stem Cell Selection and Extraction

A cost-effective immunosensor for the detection and isolation of dental pulp stem cells (DPSCs) based on a quartz crystal microbalance (QCM) has been developed. The recognition mechanism relies on anti-CD34 antibodies, DPSC-specific monoclonal antibodies that are anchored on the surface of the quartz crystals. Due to its high specificity, real time detection, and low cost, the proposed technology has a promising potential in the field of cell biology, for the simultaneous detection and sorting of stem cells from heterogeneous cell samples. The QCM surface was properly tailored through a biotinylated self-assembled monolayer (SAM). The biotin–avidin interaction was used to immobilize the biotinylated anti-CD34 antibody on the gold-coated quartz crystal. After antibody immobilization, a cellular pellet, with a mixed cell population, was analyzed; the results indicated that the developed QCM immunosensor is highly specific, being able to detect and sort only CD34+ cells. Our study suggests that the proposed technology can detect and efficiently sort any kind of cell from samples with high complexity, being simple, selective, and providing for more convenient and time-saving operations.

Analysis of the Cellular Immune Responses to Vaccines

Flow cytometry, enzyme-linked immunospot (ELISpot) and cellular cytotoxicity assays are powerful tools for studying the cellular immune response towards intracellular pathogens and vaccines in livestock species. Lymphocytes from immunized animals can be purified using Ficoll-Paque density gradient centrifugation and evaluated for their antigen specificity or reactivity towards a vaccine. Here, we describe staining of bovine lymphocytes with peptide (p)-MHC class I tetramers and antibodies specific towards cellular activation markers for evaluation by multiparametric flow cytometry, as well as interferon (IFN)-γ ELISpot and cytotoxicity using chromium ((51)Cr) release assays. A small component on the use of immunoinformatics for fine-tuning the identification of a minimal CTL epitope is included.

A method for cell type marker discovery by high-throughput gene expression analysis of mixed cell populations

BACKGROUND

Gene transcripts specifically expressed in a particular cell type (cell-type specific gene markers) are useful for its detection and isolation from a tissue or other cell mixtures. However, finding informative marker genes can be problematic when working with a poorly characterized cell type, as markers can only be unequivocally determined once the cell type has been isolated. We propose a method that could identify marker genes of an uncharacterized cell type within a mixed cell population, provided that the proportion of the cell type of interest in the mixture can be estimated by some indirect method, such as a functional assay.

RESULTS

We show that cell-type specific gene markers can be identified from the global gene expression of several cell mixtures that contain the cell type of interest in a known proportion by their high correlation to the concentration of the corresponding cell type across the mixtures.

CONCLUSIONS

Genes detected using this high-throughput strategy would be candidate markers that may be useful in detecting or purifying a cell type from a particular biological context. We present an experimental proof-of-concept of this method using cell mixtures of various well-characterized hematopoietic cell types, and we evaluate the performance of the method in a benchmark that explores the requirements and range of validity of the approach.

A framework for analytical characterization of monoclonal antibodies based on reactivity profiles in different tissues

MOTIVATION

Monoclonal antibodies (mAbs) are among the most powerful and important tools in biology and medicine. MAb development is of great significance to many research and clinical applications. Therefore, objective mAb classification is essential for categorizing and comparing mAb panels based on their reactivity patterns in different cellular species. However, typical flow cytometric mAb profiles present unique modeling challenges with their non-Gaussian features and intersample variations. It makes accurate mAb classification difficult to do with the currently used kernel-based or hierarchical clustering techniques.

RESULTS

To address these challenges, in the present study we developed a formal two-step framework called mAbprofiler for systematic, parametric characterization of mAb profiles. Further, we measured the reactivity of hundreds of new antibodies in diverse tissues using flow cytometry, which we successfully classified using mAbprofiler. First, mAbprofiler fits a mAb's flow cytometric histogram with a finite mixture model of skew t distributions that is robust against non-Gaussian features, and constructs a precise, smooth and mathematically rigorous profile. Then it performs novel curve clustering of the fitted mAb profiles using a skew t mixture of non-linear regression model that can handle intersample variation. Thus, mAbprofiler provides a new framework for identifying robust mAb classes, all well defined by distinct parametric templates, which can be used for classifying new mAb samples. We validated our classification results both computationally and empirically using mAb profiles of known classification.

AVAILABILITY AND IMPLEMENTATION

A demonstration code in R is available at the journal website. The R code implementing the full framework is available from the author website - http://amath.nchu.edu.tw/www/teacher/tilin/software

CONTACT

saumyadipta_pyne@dfci.harvard.edu

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Purification of specific cell population by fluorescence activated cell sorting (FACS)

Experimental and clinical studies often require highly purified cell populations. FACS is a technique of choice to purify cell populations of known phenotype. Other bulk methods of purification include panning, complement depletion and magnetic bead separation. However, FACS has several advantages over other available methods. FACS is the preferred method when very high purity of the desired population is required, when the target cell population expresses a very low level of the identifying marker or when cell populations require separation based on differential marker density. In addition, FACS is the only available purification technique to isolate cells based on internal staining or intracellular protein expression, such as a genetically modified fluorescent protein marker. FACS allows the purification of individual cells based on size, granularity and fluorescence. In order to purify cells of interest, they are first stained with fluorescently-tagged monoclonal antibodies (mAb), which recognize specific surface markers on the desired cell population (1). Negative selection of unstained cells is also possible. FACS purification requires a flow cytometer with sorting capacity and the appropriate software. For FACS, cells in suspension are passed as a stream in droplets with each containing a single cell in front of a laser. The fluorescence detection system detects cells of interest based on predetermined fluorescent parameters of the cells. The instrument applies a charge to the droplet containing a cell of interest and an electrostatic deflection system facilitates collection of the charged droplets into appropriate collection tubes (2). The success of staining and thereby sorting depends largely on the selection of the identifying markers and the choice of mAb. Sorting parameters can be adjusted depending on the requirement of purity and yield. Although FACS requires specialized equipment and personnel training, it is the method of choice for isolation of highly purified cell populations.

CD44 is a marker for the outer pillar cells in the early postnatal mouse inner ear

Cluster of differentiation antigens (CD proteins) are classically used as immune cell markers. However, their expression within the inner ear is still largely undefined. In this study, we explored the possibility that specific CD proteins might be useful for defining inner ear cell populations. mRNA expression profiling of microdissected auditory and vestibular sensory epithelia revealed 107 CD genes as expressed in the early postnatal mouse inner ear. The expression of 68 CD genes was validated with real-time RT-PCR using RNA extracted from microdissected sensory epithelia of cochleae, utricles, saccules, and cristae of newborn mice. Specifically, CD44 was identified as preferentially expressed in the auditory sensory epithelium. Immunohistochemistry revealed that within the early postnatal organ of Corti, the expression of CD44 is restricted to outer pillar cells. In order to confirm and expand this finding, we characterized the expression of CD44 in two different strains of mice with loss- and gain-of-function mutations in Fgfr3 which encodes a receptor for FGF8 that is essential for pillar cell development. We found that the expression of CD44 is abolished from the immature pillar cells in homozygous Fgfr3 knockout mice. In contrast, both the outer pillar cells and the aberrant Deiters' cells in the Fgfr3 ( P244R/ ) (+) mice express CD44. The deafness phenotype segregating in DFNB51 families maps to a linkage interval that includes CD44. To study the potential role of CD44 in hearing, we characterized the auditory system of CD44 knockout mice and sequenced the entire open reading frame of CD44 of affected members of DFNB51 families. Our results suggest that CD44 does not underlie the deafness phenotype of the DFNB51 families. Finally, our study reveals multiple potential new cell type-specific markers in the mouse inner ear and identifies a new marker for outer pillar cells.

Biomarker discovery in heterogeneous tissue samples -taking the in-silico deconfounding approach

Background

For heterogeneous tissues, such as blood, measurements of gene expression are confounded by relative proportions of cell types involved. Conclusions have to rely on estimation of gene expression signals for homogeneous cell populations, e.g. by applying micro-dissection, fluorescence activated cell sorting, or in-silico deconfounding. We studied feasibility and validity of a non-negative matrix decomposition algorithm using experimental gene expression data for blood and sorted cells from the same donor samples. Our objective was to optimize the algorithm regarding detection of differentially expressed genes and to enable its use for classification in the difficult scenario of reversely regulated genes. This would be of importance for the identification of candidate biomarkers in heterogeneous tissues.

Results

Experimental data and simulation studies involving noise parameters estimated from these data revealed that for valid detection of differential gene expression, quantile normalization and use of non-log data are optimal. We demonstrate the feasibility of predicting proportions of constituting cell types from gene expression data of single samples, as a prerequisite for a deconfounding-based classification approach.

Classification cross-validation errors with and without using deconfounding results are reported as well as sample-size dependencies. Implementation of the algorithm, simulation and analysis scripts are available.

Conclusions

The deconfounding algorithm without decorrelation using quantile normalization on non-log data is proposed for biomarkers that are difficult to detect, and for cases where confounding by varying proportions of cell types is the suspected reason. In this case, a deconfounding ranking approach can be used as a powerful alternative to, or complement of, other statistical learning approaches to define candidate biomarkers for molecular diagnosis and prediction in biomedicine, in realistically noisy conditions and with moderate sample sizes.

Intracellular staining for analysis of the expression and phosphorylation of signal transducers and activators of transcription (STATs) in NK cells

Cytokines stimulate biological responses by activating intracellular signaling pathways. We have been adapting flow cytometric techniques to measure the levels of expression and activation of signaling molecules within mixed populations containing NK cells and to characterize their differences within NK cell subpopulations. Approaches for evaluating the total levels of the signal transducers and activators of transcription STAT1 and STAT4, of STAT1 in cells expressing IFNgamma, and of the type 1 interferon (type 1 IFN) activation by phosphorylation, i.e., induction of pSTAT1 and pSTAT4, have been developed. The results of experiments using these techniques have demonstrated that an unusual feature of NK cells is high basal expression of STAT4 but reduced STAT1 levels. The condition predisposes for pSTAT4 activation by type 1 IFNs. The work has also shown, however, that total STAT1 levels are induced during viral infections as a result of IFN exposure, and that this change acts to promote the activation of STAT1 but limit both the activation of STAT4 and IFNgamma expression. The intracellular staining approaches used for the studies described here have utility in characterizing other mechanisms regulating cytokine-mediated signaling, and defining additional pathways shaping cellular responses to cytokines.

Investigating T cells by polychromatic flow cytometry

Since its development, flow cytometry gave a relevant contribution to the field of Immunology. Its unique potential to analyse multiple parameters at the single cell level allowed the identification of unknown cell subsets with specific roles in immunoregulation as well as in the pathogenesis of several diseases. More recently, with the advent of new equipments and fluorochromes, the possibility exists to analyse simultaneously a large number (up to 19) of parameters in a single cell. This strategy, defined polychromatic flow cytometry (PFC), has been widely utilised in the last years for the fine analysis of immune cell phenotypes, including antigen-specific T lymphocytes, B cell subsets, and the intracellular phosphoproteome, among others. A huge amount of data can be generated by such an approach, and their interpretation could become a very complex and time-consuming task. Protocols for performing PFC will be discussed in this chapter, together with some guidelines for data interpretation and analysis.

Phenotypic analysis of B-cells and plasma cells

B-cells and antibody-secreting plasma cells are key players in protective immunity, but also in autoimmune disease. To understand their various functions in the initiation and maintenance of autoimmune pathology, a detailed dissection of their functional diversity is mandatory. This requires a detailed phenotypic classification of the diversity of B-cells. Here, technologies of immunocytometry and ELISpot are described in detail, and their value for phenotypic characterization of cells of the B lineage, as well as for preparative cell sorting, to further characterize them functionally and on the molecular level are described.

Development of separation technique for stem cells

In recent years, human embryonic stem cells have been established, and somatic stem cells derived from various adult organs have been identified and characterized to differentiate into various kinds of functional cells. There have been attempts to use functional cells induced from such stem cells for tissue regeneration and cell therapy. The method is expected to become an important treatment for intractable diseases in the near future. Since tissues and organs generally contain only a small quantity of somatic stem cells, and since it is necessary to separate functional cells generated from stem cells for use in therapy, an effective method for specific cell separation is crucial to the practical application of regenerative medicine. For the specific separation of cells, a fluorescence activated cell sorter using specific antibodies is a powerful tool, but the method is not suitable for large-scale processing and a special device is required. Although a magnetic cell separation system using immuno-magnetic fine particles is also commercially available, the system still needs special apparatus for large-scale processing. We developed a novel method for the separation of specific cells in an aqueous two-phase system using antibodies modified with a temperature-responsive polymer. The method enables the processing of a large quantity of cells without the requirement of a special device.

Dynamic imaging of the immune system: progress, pitfalls and promise

Both innate and adaptive immunity are dependent on the migratory capacity of myeloid and lymphoid cells. Effector cells of the innate immune system rapidly enter infected tissues, whereas sentinel dendritic cells in these sites mobilize and transit to lymph nodes. In these and other secondary lymphoid tissues, interactions among various cell types promote adaptive humoral and cell-mediated immune responses. Recent advances in light microscopy have allowed direct visualization of these events in living animals and tissue explants, which allows a new appreciation of the dynamics of immune-cell behaviour. In this article, we review the basic techniques and the tools used for in situ imaging, as well as the limitations and potential artefacts of these methods.

A novel monoclonal antibody against canine monocytes/macrophages

The production and partial characterization of a monoclonal antibody, the IgG1 IH1, which recognizes an antigen distributed in canine monocytes/macrophages, is reported here. The distribution and apparent molecular weight of the antigen recognized by the IH1 MAb was determined in peripheral blood leukocytes, peripheral blood monocyte-derived macrophages and tissue sections of spleen, liver and skin, using Western blotting, immunocytochemistry, immunohistochemistry and flow cytometry. The IH1 MAb-recognized antigen was detected in Western blotting under non-reducing conditions spread out as a large band covering the position corresponding to the migration of molecules with molecular weights from 55 to 73 kDa. The IH1 MAb labeled blood monocytes, tissue macrophages in lymph nodes, and in the mantle zone of the spleen, and Kupffer cells in the liver. It did not react with human cells. In flow cytometric analysis, the IH1 MAb reacted with a subpopulation of monocytes. The MAb described herein may become a valuable tool for diagnosis and research on canine diseases.

Antibody microarray for correlating cell phenotype with surface marker

To correlate cell surface markers with the cell phenotype, an antibody microarray prepared by covalently immobilizing antibodies onto a cellulose membrane and subsequent immunocytochemical staining were employed. The direct binding assay of a lymphoblastic leukemia cell line on the microarray showed that the immobilized antibody served to capture cells expressing the specific antigen. The density of bound cells increased linearly with an increasing content of antigen-expressing cells in suspension. The method was further applied to the analysis of surface antigens expressed on neural stem cells. A binding assay was performed with neural cells obtained from the neurosphere culture of the rat fetal striatum on a microarray spotted with eight kinds of antibodies and four different proteins, followed by immunocytochemical staining of cells bound to the microarray using antibodies to the intracellular markers of immature (nestin and vimentin) and mature (beta-tubulin III and glial fibrillary acidic protein) neural cells. As a result, the phenotype of bound cells could be correlated to surface antigen expression, which illustrated the potential of the solid-phase cytometry developed here for the identification of surface markers.

Virus Specific T-Cell Responses

CD8+ and CD4+ T-cells play a key role in the maintenance of our immunity against viruses. Recent technological developments, such as the use of MHC-peptide tetrameric complexes, have permitted significant improvements in the study of these cells. It is now possible to assess precisely frequencies as well as phenotypic and functional features of virus specific T-cells from the onset of many viral infections onwards. Different virus specific T-cell populations exhibit distinct functional characteristics and can be positioned at different stages of a process of post-thymic development, which we are drawing near to understanding the significance. Still, further work is needed before consensus is reached as regards what defines and how to induce the optimal virus specific T-cell response which will confer long lasting immunological protection in humans.

Production of Monoclonal Antibodies Against Canine Leukocytes

A panel of anti-canine leukocyte monoclonal antibodies (MAbs) was produced by immunizing BALB/c mice with canine peripheral blood mononuclear cells (PBMC), either resting or stimulated with concanavalin A (ConA). Three out of 28 clones-IH1, AB6, and HG6-screened by ELISA and producing antibody with the highest specificity for canine cell immunostaining, were subjected to three subsequent subcloning steps by limiting dilution, and selected for further characterization. These MAbs belonged to IgG1 (HG6 and IH1) and IgG2a (AB6) isotypes. The distribution of cell populations expressing the antigen recognized by the antibodies was identified by indirect immunoflorescence on canine PBMC and on tissue sections of lymph node, spleen, liver and skin. The possible crossreactivity with human PBMC was also examined in immunocytochemistry. One of the antibodies specifically recognized macrophages. The MAbs presented here can be foreseen as possible valuable diagnostic and research tools to study immune functions in dogs.

Immunophenotypic analysis of human articular chondrocytes: Changes in surface markers associated with cell expansion in monolayer culture

Cartilage tissue engineering relies on in vitro expansion of primary chondrocytes. Monolayer is the chosen culture model for chondrocyte expansion because in this system the proliferative capacity of chondrocytes is substantially higher compared to non-adherent systems. However, human articular chondrocytes (HACs) cultured as monolayers undergo changes in phenotype and gene expression known as "dedifferentiation." To gain a better understanding of the cellular mechanisms involved in the dedifferentiation process, our research focused on the characterization of the surface molecule phenotype of HACs in monolayer culture. Adult HACs were isolated by enzymatic digestion of cartilage samples obtained post-mortem. HACs cultured in monolayer for different time periods were analyzed by flow cytometry for the expression of cell surface markers with a panel of 52 antibodies. Our results show that HACs express surface molecules belonging to different categories: integrins and other adhesion molecules (CD49a, CD49b, CD49c, CD49e, CD49f, CD51/61, CD54, CD106, CD166, CD58, CD44), tetraspanins (CD9, CD63, CD81, CD82, CD151), receptors (CD105, CD119, CD130, CD140a, CD221, CD95, CD120a, CD71, CD14), ectoenzymes (CD10, CD26), and other surface molecules (CD90, CD99). Moreover, differential expression of certain markers in monolayer culture was identified. Up-regulation of markers on HACs regarded as distinctive for mesenchymal stem cells (CD10, CD90, CD105, CD166) during monolayer culture suggested that dedifferentiation leads to reversion to a primitive phenotype. This study contributes to the definition of HAC phenotype, and provides new potential markers to characterize chondrocyte differentiation stage in the context of tissue engineering applications.

[Production of a new monoclonal anti-AB reagent]

Techniques of monoclonal antibodies production have well progressed in the developed countries. But, they are still absent in the third world. In this report, the murine hybridoma technology was performed to produce anti-ABH monoclonal antibodies. The anti-AB specificity of several hybridomas was determined by agglutination techniques using phenotyped red cells panels. An anti-AB monoclonal antibody was selected and compared to other reagents for its use as a blood grouping reagent. Its characteristics were in accordance with the international standards. Hybridoma establishment to produce a good monoclonal reagent is henceforth possible in Morocco.

Affibody-beta-galactosidase immunoconjugates produced as soluble fusion proteins in the Escherichia coli cytosol

Recombinant immunoconjugates constitute a novel class of immunoassay reagents produced by genetic fusion between an antigen recognizing moiety and a reporter enzyme or fluorescent protein, obviating the need for chemical coupling. In this work, we describe the construction, Escherichia coli production and characterization of recombinant beta-galactosidase (beta-gal)-based immunoconjugates directed to human immunoglobulin A (IgA). As the antigen recognizing moieties, either monovalent or dimeric (head-to-tail) versions of an IgA-specific affibody (Z(IgA1)) were used, previously selected in vitro from a protein library based on combinatorial engineering of a single staphylococcal protein A domain. To increase the likelihood of proper presentation on the assembled homotetrameric enzyme surface, the affibody moieties were linked to the N-terminus of the enzyme subunits via a heptapeptide linker sequence. The two resulting immunoconjugates Z(IgA1)-beta-gal and (Z(IgA1))(2)-beta-gal, containing four and eight affibody moieties per enzyme, respectively, could be expressed as soluble and proteolytically stable proteins intracellularly in E. coli from where they were purified to high purity by a single anion exchange chromatography step. The yields of immunoconjugates were in the range 200-400 mg/l culture. Biosensor-binding studies showed that both the Z(IgA1)-beta-gal and (Z(IgA1))(2)-beta-gal immunoconjugates were capable of selective IgA-recognition, but with an apparent higher binding affinity for the variant containing divalent affibody moieties, presumably due to avidity effects. The applicability of this class of recombinant immunoconjugates was demonstrated by IgA detection in enzyme-linked immunosorbent assay (ELISA) and dot-blot analyses. In addition, using human kidney biopsy samples from a nephropathy patient, IgA depositions in glomeruli could be detected by immunohistochemistry with low background staining of tissue.

Expression deconvolution: a reinterpretation of DNA microarray data reveals dynamic changes in cell populations

Cells grow in dynamically evolving populations, yet this aspect of experiments often goes unmeasured. A method is proposed for measuring the population dynamics of cells on the basis of their mRNA expression patterns. The population's expression pattern is modeled as the linear combination of mRNA expression from pure samples of cells, allowing reconstruction of the relative proportions of pure cell types in the population. Application of the method, termed expression deconvolution, to yeast grown under varying conditions reveals the population dynamics of the cells during the cell cycle, during the arrest of cells induced by DNA damage and the release of arrest in a cell cycle checkpoint mutant, during sporulation, and following environmental stress. Using expression deconvolution, cell cycle defects are detected and temporally ordered in 146 yeast deletion mutants; six of these defects are independently experimentally validated. Expression deconvolution allows a reinterpretation of the cell cycle dynamics underlying all previous microarray experiments and can be more generally applied to study most forms of cell population dynamics.

B-1 cell (CD5+/CD11b+) numbers and nIgM levels are elevated in physically active vs. sedentary rats

Habitual, moderate exercise is associated with improved health, including reductions in illness. These benefits may stem, in part, from immune function improvements. We have previously reported that daily wheel running increases serum and peritoneal natural IgM (nIgM) in pathogen-free Sprague-Dawely rats. B-1 cells, which primarily reside in the peritoneal cavity, produce nIgM in the absence of antigen stimulation. This study examined whether physical activity would also increase B-1 cell numbers in the peritoneal cavity, mesenteric lymph nodes, and spleen. Male, pathogen-free Fischer 344 rats were sedentary (standard cages) or physically active (running wheel access) for 6-7 wk. Peritoneal cavity, mesenteric lymph nodes, and spleen cells were taken, and the number of CD5+/CD11b+ (B-1) cells were measured by using two-color flow cytometry. The results were that physically active animals had increased numbers of CD5+/CD11b+ cells in the peritoneal cavity. In addition, physically active animals had increased serum and peritoneal nIgM, thus replicating our previous observations. These results indicate that voluntary running selectively increases the B-1 cell population, which is most likely responsible for the elevated serum and peritoneal nIgM in active rats. Because B-1 cells are important in host defense, these changes may contribute to the health benefits of exercise.

Flow cytometric analysis of macaque whole blood for antigen-specific intracellular cytokine production by T lymphocytes

We report here the standardized conditions for stimulation of macaque whole blood samples with various protein or peptide antigens, and production of significant intracellular levels of interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) in CD4+ as well as CD8+ T lymphocytes. We observed significantly higher levels of TNF-alpha compared with IFN-gamma in both CD4+ and CD8+ T lymphocytes from all the macaque whole blood samples stimulated with staphylococcal enterotoxin B (SEB) as an antigen. Similarly, when whole blood samples from rhesus macaques immunized with an HIV envelope peptide cocktail vaccine were stimulated with either the peptide cocktail or recombinant gp160, we observed production of significant levels of TNF-alpha by both CD4+ and CD8+ T lymphocytes. These results strongly support the utility of the whole blood cytokine flow cytometry methodology for determining antigen-specific immune responses of macaques in vaccine studies.

Inflammatory signals increase Fas ligand expression by inner ear cells

There is considerable evidence that hearing and vestibular function can be influenced by immune processes. The inner ear has evolved mechanisms, such as the blood-labyrinthine barrier that limit immune responses and autoimmune processes to reduce the potential for damage to cochlear cells. Recently, expression of Fas ligand (FasL) in some non-lymphoid tissue, as in the anterior chamber of the eye, has been hypothesized to play a role in protection of sensitive organs from activated T-cells. We show that under resting conditions, cochlear cells express little or no FasL. However, after exposure to interferon-gamma in vitro, FasL is induced in many neonatal cochlear cells. In addition, we show that FasL is upregulated in adult cochlear cells after induction of a sterile labyrinthitis in vivo. The induction of FasL by inflammation may serve to limit cochlear immune responses, and to protect sensorineural tissue from immune and autoimmune damage.

Miniaturised multiplexed immunoassays

Miniaturised immunoassays are of general interest for applications that require the simultaneous determination of different parameters from a minute sample of material. Apart from planar microarray-based systems, bead-based flow cytometric approaches are well suited for the multiplexed detection of target molecules, especially when the number of parameters that have to be determined in parallel is limited.