Nine color eleven parameter immunophenotyping using three laser flow cytometry

WebFlow: a software package for high-throughput analysis of flow cytometry data

Flow cytometry has emerged as a powerful tool for quantitative, single-cell analysis of both surface markers and intracellular antigens, including phosphoproteins and kinase signaling cascades, with the flexibility to process hundreds of samples in multiwell plate format. Quantitative flow cytometric analysis is being applied in many areas of biology, from the study of immunology in animal models or human patients to high-content drug screening of pharmacologically active compounds. However, these experiments generate thousands of data points per sample, each with multiple measured parameters, leading to data management and analysis challenges. We developed WebFlow (http://webflow.stanford.edu), a web server-based software package to manage, analyze, and visualize data from flow cytometry experiments. WebFlow is accessible via standard web browsers and does not require users to install software on their personal computers. The software enables plate-based annotation of large data sets, which provides the basis for exploratory data analysis tools and rapid visualization of multiple different parameters. These tools include custom user-defined statistics to normalize data to other wells or other channels, as well as interactive, user-selectable heat maps for viewing the underlying single-cell data. The web-based approach of WebFlow allows for sharing of data with collaborators or the general public. WebFlow provides a novel platform for quantitative analysis of flow cytometric data from high-throughput drug screening or disease profiling experiments.

Differential response of human basophil activation markers: a multi-parameter flow cytometry approach

BACKGROUND

Basophils are circulating cells involved in hypersensitivity reactions and allergy but many aspects of their activation, including the sensitivity to external triggering factors and the molecular aspects of cell responses, are still to be focused. In this context, polychromatic flow cytometry (PFC) is a proper tool to investigate basophil function, as it allows to distinguish the expression of several membrane markers upon activation in multiple experimental conditions.

METHODS

Cell suspensions were prepared from leukocyte buffy coat of K2-EDTA anticoagulated blood specimens; about 1500-2500 cellular events for each tested sample, gated in the lymphocyte CD45dim area and then electronically purified as HLADRnon expressing/CD123bright, were identified as basophilic cells. Basophil activation with fMLP, anti-IgE and calcium ionophore A23187 was evaluated by studying up-regulation of the indicated membrane markers with a two-laser six-color PFC protocol.

RESULTS

Following stimulation, CD63, CD13, CD45 and the ectoenzyme CD203c up-regulated their membrane expression, while CD69 did not; CD63 expression occurred immediately (within 60 sec) but only in a minority of basophils, even at optimal agonist doses (in 33% and 14% of basophils, following fMLP and anti-IgE stimulation respectively). CD203c up-regulation occurred in the whole basophil population, even in CD63non expressing cells. Dose-dependence curves revealed CD203c as a more sensitive marker than CD63, in response to fMLP but not in response to anti-IgE and to calcium ionophore.

CONCLUSION

Use of polychromatic flow cytometry allowed efficient basophil electronic purification and identification of different behaviors of the major activation markers. The simultaneous use of two markers of activation and careful choice of activator are essential steps for reliable assessment of human basophil functions.

Beyond 51Cr release: New methods for assessing HIV-1-specific CD8+ T cell responses in peripheral blood and mucosal tissues

Much scientific effort has been directed towards elucidating the complexities of cell-mediated immune responses to HIV-1(reviewed in [1,2]). These studies have attempted to explain the immune system's ultimate failure to contain viral replication, leading to development of AIDS disease, and to identify immune responses that will be useful in developing immunomodulatory therapies and novel vaccine strategies. Although many of the complex interactions involved in AIDS pathogenesis remain unsolved, great progress has been made in characterizing the kinetics, specificity and functional dynamics of HIV-1-specific T cell responses. These investigations have come at a time when advances in virology, cellular immunology and molecular biology have converged to provide a variety of methodological approaches not available at the onset of the AIDS pandemic. Application of these tools to other infectious diseases and immunopathological conditions will provide a fertile area of research for future years. This review focuses on recent developments in the assessment of HIV-1-specific T cell responses in peripheral blood and tissues, with a particular emphasis on flow cytometry-based approaches.

IkappaB kinase signaling is essential for maintenance of mature B cells

Nuclear factor (NF)-kappaB proteins play crucial roles in immune responses and cellular survival. Activation of NF-kappaB is mediated by the IkappaB kinase (IKK) complex, which is composed of two kinases, IKK1 and IKK2, and a regulatory subunit termed NF-kappaB essential modulator (NEMO). IKK2- and NEMO-deficient mice die at early embryonic stages. We therefore used conditional gene targeting to evaluate the role of these proteins in B cells in adult mice. B lineage-specific disruption of either IKK signaling by deletion of NEMO, or of IKK2-specific signals by ablation of IKK2 activity leads to the disappearance of mature B lymphocytes. We conclude that maintenance of mature B cells depends on IKK-mediated activation of NF-kappaB.

Identification of a germ-line pro-B cell subset that distinguishes the fetal/neonatal from the adult B cell development pathway

Studies presented here show that the expression of CD4, MHC class II (Ia,) and B220 cleanly resolves a major and a minor subset within the earliest pro-B cell population (germ-line pro-B) in adult bone marrow (BM). The major subset expresses intermediate B220 and low CD4 levels. The minor subset, which constitutes roughly 20% of the adult germ-line pro-B, expresses very low B220 levels and does not express CD4. Ia is clearly detectable at low levels on the major germ-line pro-B subset, both in wild-type adult mice and in gene-targeted mice (RAG2-/- and microMT), in which B cell development terminates before the pre-B cell stage. A small proportion of cells in the more mature pro-B cell subsets (Hardy Fractions B and C) also express Ia at this level. In contrast, Ia levels on the minor subset are barely above (or equal to) background. Surprisingly, the major germ-line pro-B cell subset found in adults is missing in fetal and neonatal animals. All of the germ-line pro-B in these immature animals express a phenotype (very low B220, no CD4, or Ia) similar to that of the minor pro-B cell subset in adult BM. Because B cell development in fetal/neonatal animals principally results in B-1 cells, these findings demonstrate that the B-1 development pathway does not include the major germ-line pro-B subset found in adult BM and hence identify a very early difference between the B-1 and -2 development pathways.

Recent developments in flow cytometry

Flow cytometry has experienced considerable expansion of available parameters during the last years. Various new techniques that allow the direct analysis of antigen-specific lymphocytes by direct labeling with antigen or according to functional parameters following in vitro antigen stimulation will have enormous impact on immunological research, diagnosis, and therapy. This article concentrates on the basic principles and applications of these important technological developments in flow cytometry and focuses on the analysis of specific lymphocytes.

B-1 and B-2 cell-derived immunoglobulin M antibodies are nonredundant components of the protective response to influenza virus infection

We have studied the role of secreted immunoglobulin (Ig)M in protection from infection with influenza virus and delineated the relative contributions of B-1 versus B-2 cell-derived IgM in this process. Mice deficient in secreted IgM but capable of expressing surface IgM and secreting other Ig classes show significantly reduced virus clearance and survival rates compared with wild-type controls. Irradiation chimeras in which only either B-1 or B-2 cells lack the ability to secrete IgM show mortality rates similar to those of mice in which neither B-1 nor B-2 cells secrete IgM. Dependence on both sources of IgM for survival is partially explained by findings in allotype chimeras that broadly cross-reactive B-1 cell-derived natural IgM is present before infection, whereas virus strain-specific, B-2 cell-derived IgM appears only after infection. Furthermore, lack of IgM secreted from one or both sources significantly impairs the antiviral IgG response. Reconstitution of chimeras lacking B-1 cell-derived IgM only with IgM-containing serum from noninfected mice improved both survival rates and serum levels of virus-specific IgG. Thus, virus-induced IgM must be secreted in the presence of natural IgM for efficient induction of specific IgG and for immune protection, identifying B-1 and B-2 cell-derived IgM antibodies as nonredundant components of the antiviral response.

CD4+ T cells derived from B cell-deficient mice inhibit the establishment of peripheral B cell pools

We demonstrate that adoptive transfer of peritoneal cavity B cells fails to replenish the peripheral B-1 cells in adult B cell-deficient (mu(-/-)) mice but does replenish adult RAG-1(-/-) mice. We show that this lack of self-replenishment in mu(-/-) mice is mediated by strongly inhibitory, radiation-sensitive CD4(+) T cells that also function in cotransfer studies to block the reconstitution of B-1 cells and inhibit accumulation of bone marrow-derived B-2 cells in the periphery in irradiated recipients. CD8(+) T cells from mu(-/-) do not mediate this inhibition. The inhibitory CD4(+) T cells develop early in life, because B-1 cell replenishment occurs normally when B-1 cells are transferred into mu(-/-) neonates. Thus, we conclude that the presence of B cells in the neonate conditions the CD4(+) T-cell population to permit the establishment and maintenance of normal B cell pools throughout life.

Use of reporter genes for optical measurements of neoplastic disease in vivo

Revealing the cellular and molecular changes associated with cancer, as they occur in intact living animal models of human neoplastic disease, holds tremendous potential for understanding disease mechanisms and elucidating effective therapies. Since light is transmitted through mammalian tissues, at a low level, optical signatures conferred on tumor cells by expression of reporter genes encoding bioluminescent and fluorescent proteins can be detected externally using sensitive photon detection systems. Expression of reporter genes, such as the bioluminescent enzyme firefly luciferase (Luc) or variants of green fluorescent protein (GFP) in transformed cells, can effectively be used to reveal molecular and cellular features of neoplasia in vivo. Tumor cell growth and regression in response to various therapies have been evaluated non-invasively in living experimental animals using these reporter genes. Detection of Luc-labeled cells in vivo was extremely sensitive with signals over background from as few as 1000 human tumor cells distributed throughout the peritoneal cavity of a mouse with linear relationships between cell number and signal intensity over five logs. GFP offers the strength of high-resolution ex vivo analyses following in vivo localization of the tumor. The dynamic range of Luc detection allows the full disease course to be monitored since disease progression from small numbers of cells to extensive disease can be assessed. As such, therapies that target minimal disease as well as those designed for late stage disease can be readily evaluated in animal models. Real time spatiotemporal analyses of tumor cell growth can reveal the dynamics of neoplastic disease, and facilitate rapid optimization of effective treatment regimens. Thus, these methods improve the predictability of animal models of human disease as study groups can be followed over time, and can accelerate the development of therapeutic strategies.