Chapter 41 Identafication and Purafication of Murine Hematopoietic Stem Cellsby Flow Cytometry

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Primed innate immunity leads to autoinflammatory disease in PSTPIP2-deficient cmo mice

The mouse Lupo (I282N) mutation in proline-serine-threonine phosphatase-interacting protein 2 (PSTPIP2) leads to reduced expression of PSTPIP2 that is associated with a macrophage-mediated autoinflammatory disease. Another mutation in PSTPIP2, L98P, termed chronic multifocal osteomyelits (cmo), leads to a disease in mice that resembles chronic recurrent multifocal osteomyelits in humans. The cellular basis of cmo disease was investigated. cmo disease develops independently of lymphocytes and is cured by bone marrow transplantation. Macrophages, mast cells, and osteoclasts from cmo mice fail to express detectable PSTPIP2 protein. Asymptomatic Pstpip2(cmo/cmo) mice have increased circulating levels of macrophage inflammatory protein 1-alpha and interleukin-6, and their macrophages exhibit increased production of these inflammatory mediators, which is normalized by retroviral expression of wild-type PSTPIP2. Spleens of asymptomatic cmo mice contain increased numbers of macrophage precursors, and cmo mice mobilize more macrophage precursors in response to a sterile inflammatory stimulus. Signal transducer and activator of transcription 1 is elevated in cmo splenic macrophages, which also exhibit increased colony-stimulating factor-1-stimulated proliferation and increased extracellular signal-regulated kinase 1/2 phosphorylation. PSTPIP2 overexpression in macrophages leads to the opposite phenotype. Thus, PSTPIP2 deficiency causes both an expansion of macrophage progenitors and increased responsiveness of mature macrophages to activating stimuli, which together prime the organism for exaggerated and sustained responses leading to autoinflammatory disease.

Phenotypic comparison of multiple monocyte-related populations in murine peripheral blood and bone marrow

BACKGROUND

Monocyte subsets are not well defined in murine peripheral blood (PB). Monocyte-related populations could also be located in bone marrow (BM), but studies correlating monocyte populations found in these two tissues are lacking. This study simultaneously analyzed PB and BM to phenotypically define multiple monocyte-related subsets in each location.

METHODS

Murine PB and BM cells were simultaneously stained for monocyte-related populations, using five-color flow cytometry. Relevant subsets were defined on the basis of Ly-6C, CD11b, and wheat germ agglutinin phenotype in addition to light-scatter characteristics. These populations were extensively characterized for the expression of other myeloid and dendritic cell markers, adhesion molecules, chemokine receptors, and growth factor receptors.

RESULTS

Six monocyte-related populations were defined, three each in BM and PB. No identical populations were found between the two tissues. Two BM populations and one PB population have heterogeneous expression of many markers, suggesting additional complexity among monocyte-related subsets.

CONCLUSIONS

The murine monocytic series comprises multiple subsets, differing between PB and BM. This study defines and extensively phenotypes six of these populations, providing preliminary information about possible developmental relationships and migratory capacities of these cells.

Absence of cross-reactivity between murine Ly-6C and Ly-6G

BACKGROUND

The Ly-6 family has many members, including Ly-6C and Ly-6G. A previous study suggested that the anti-Ly-6G antibody, RB6-8C5, may react with Ly-6Chi murine bone marrow (BM) cells. This finding has been interpreted as cross-reactivity of RB6-8C5 with the Ly-6C antigen, and has been generalized to many hematopoietic cell types, using the terminology Ly-6G/C. The present study was undertaken to determine whether anti-Ly-6G antibodies truly cross-react with the Ly-6C antigen on multiple hematopoietic cell types.

METHODS

Splenocytes, thymocytes, and BM cells obtained from Ly-6.1 and Ly-6.2 strains of mice were stained with a variety of antibodies to Ly-6C and Ly-6G. Flow cytometric analysis was performed on these populations.

RESULTS

Evaluation of anti-Ly-6C and anti-Ly-6G staining showed only Ly-6C expression and no Ly-6G expression on subsets of splenic T and B cells and thymocytes from Ly-6.1 and Ly-6.2 mice. Bone marrow cells were identified that express both Ly-6G and Ly-6C; no Ly-6G+Ly-6C- populations were seen.

CONCLUSIONS

Multiple Ly-6C+ hematopoietic cell populations were identified that do not stain with anti-Ly-6G antibodies. This calls into question the use of the Ly-6G/C nomenclature and suggests that epitopes recognized by anti-Ly-6G antibodies should simply be designated Ly-6G.

B cells express Ly-6C in a Th1 but not Th2 cytokine environment

Interferon-alpha (IFN-alpha) is the primary regulator of transient Ly-6C expression on T cells. B cells, which do not express Ly-6C in the resting state, have been reported to express Ly-6C following exposure to proinflammatory stimuli. This study examined the factors controlling Ly-6C expression on B cells and the kinetics of Ly-6C expression in the presence of these factors. In vivo studies demonstrated that proinflammatory (Th1) cytokines transiently upregulate B cell Ly-6C expression. In vitro studies identified Th1 cytokines, particularly IFN-alpha and IFN-gamma, as the principal cytokines responsible for this induction. Polyclonal B cell activators (anti-IgM and recombinant CD40 ligand trimer) showed minimal ability to independently induce Ly-6C expression on B cells but did enhance the ability of IFNs to induce expression. Th2 cytokine environments did not result in B cell Ly-6C expression, and interleukin-4 (IL-4) actually antagonized the IFN-driven induction of Ly-6C. Ly6.1 strains of mice consistently demonstrated a greater ability to express Ly-6C on B cells than did Ly-6.2 strains. Together, these studies demonstrate the ability of Th1 but not Th2 cytokine environments to transiently induce the expression of Ly-6C on B cells and provide additional evidence for differences in the regulation of Ly-6C expression in Ly6.1 and Ly6.2 strains.

Type I interferon is the primary regulator of inducible Ly-6C expression on T cells

Ly-6C has been proposed as a marker of memory CD8+ T cells. Reports have indicated that Ly-6C is upregulated after T cell receptor (TCR) stimulation or exposure to proinflammatory cytokines. This study examined the relative roles of proinflammatory cytokines and TCR engagement in Ly-6C induction. In vitro experiments tested the effects of cytokines on Ly-6C expression and confirmed interferon-alpha (IFN-alpha) as a primary cytokine that induces Ly-6C expression on CD4+ and CD8+ T cells. The amount and duration of Ly-6C expression were examined on T cells after in vivo induction of proinflammatory cytokines (CpG oligodeoxynucleotides [ODN]) or TCR activation (staphylococcal enterotoxin B [SEB]). In vivo, proinflammatory cytokines transiently upregulated Ly-6C on T cells in the absence of TCR stimulation. TCR stimulation by SEB transiently upregulated Ly-6C expression on antigen-specific and antigen-nonspecific T cells but did not cause long-term upregulation of Ly-6C expression in either population. IFN-alpha was confirmed as a primary inducer of Ly-6C in vivo, as CpG ODN were unable to induce Ly-6C expression in IFN-alphaRI(-/-) mice. Thus, inducible Ly-6C expression on CD4+ and CD8+ T cells is largely due to IFN-alpha in the environment and appears not to be directly correlated with the development of T cell memory.

Delineation among eight major hematopoietic subsets in murine bone marrow using a two-color flow cytometric technique

BACKGROUND

Many methods have been developed specifically for identifying hematopoietic progenitor cells in murine bone marrow, but few methods allow rapid identification of multiple bone marrow populations. We describe a new, simple method for identifying simultaneously eight populations in murine bone marrow with two-color flow cytometry and phenotypically define these populations.

METHODS

Bone marrow was stained with anti-Ly-6C and anti-B220 (CD45R) in one fluorochrome and wheat germ agglutinin (WGA) in another fluorochrome. The eight populations identified in this way were defined further primarily by four-color flow cytometry.

RESULTS

Six of the eight populations were characterized phenotypically as containing erythroid, granulocytic, mast, early B, mature B, and stem cell populations. Two additional populations with phenotypic characteristics of partially differentiated precursor cells also were identified. One population was Ly-6C/B220+ and WGA-. It also expressed markers associated with early B, T, and/or dendritic cell differentiation. The second population was Ly-6C(hi)WGA(hi)Mac-1+ and was negative for numerous other lineage-specific and precursor markers. Its morphology suggested monocytic differentiative potential.

CONCLUSIONS

A two-color flow cytometric assay profiles six bone marrow populations with identifiable phenotypes and two additional unique, putative hematopoietic precursor populations.

Increased levels of apoptosis of leukocyte subsets in cultured PBMCs compared to whole blood as shown by Annexin V binding: relevance to cytokine production

Most of the investigatory studies of cytokine production by cells have been performed on purified cells or cell lines by measuring the secreted cytokine levels in the bulk culture supernatant. However, results of cytokine production from isolated peripheral blood mononuclear cells (PBMCs) cultivated in synthetic media, have been reported to be inaccurate and of low reproducibility. Isolation procedures have been shown to be toxic to certain cells. We hypothesised that purified cell culture techniques may result in increased levels of apoptosis of cells compared with whole blood culture techniques. To compare the effects on cell viability between PBMCs and whole blood techniques, an Annexin V binding assay was utilised. The effect of different cell concentration and serum/plasma concentrations on apoptosis levels in the various leukocyte subsets in PBMC and whole blood cultures following stimulation was investigated. There were significantly increased levels of apoptosis of cells in PBMC compared to whole culture at similar plasma concentrations, suggesting that cell viability was plasma concentration-dependent. There were significantly increased levels of apoptosis in PBMC cultures at the same cell concentration to whole blood techniques, suggesting that interaction between all cellular elements (as in whole blood techniques) is important in maintaining cell viability. These results suggest that whole blood culture techniques provide the best conditions for study of leukocyte cytokine production. If PBMC culture is performed, similar plasma and cell concentration to whole blood will best preserve cell viability.

Analysis of gene expression in subpopulations of murine hematopoietic stem and progenitor cells

OBJECTIVE

The aim of the present work was to study how functional differences between subsets of the murine hematopoietic stem/progenitor cell compartment are manifested on the level of different patterns of gene expression in these subsets.

MATERIALS AND METHODS

Amplified 3' terminal total cDNA fragment populations from four stem and progenitor cell fractions sorted using differential staining with Rhodamine 123 were prepared, and gene expression patterns were analyzed by Southern hybridization with a panel of gene markers.

RESULTS

For the vast majority of lineage-specific markers, no expression was detected in the long-term repopulating stem cell fraction. Expression of a number of key genes positively regulating entry and progression through the cell cycle was down-regulated in long-term repopulating cells, in accordance with the quiescent state of the latter. In contrast, certain but not all cell division kinase inhibitors were significantly up-regulated in long- and short-term repopulating stem cell fractions. Expression of several genes important for entry into the apoptotic pathway was moderately reduced in long-term repopulating cells. Messenger RNA levels of the transcription factors GATA-1, GATA-2, c-Myb and SCL were down-regulated in long-term repopulating cells, as compared to more mature stem/progenitor cells. Finally, expression of the MDR1a gene encoding the Pgp efflux pump was highest in long-term repopulating cells, and progressively decreased with maturation.

CONCLUSION

The patterns of gene expression in the stem/progenitor cell fractions are in good correlation with the known properties of adult hematopoietic stem/progenitor cells and may provide insight into molecular mechanisms underlying stem cell physiology.

Optimal storage conditions for preserving granulocyte viability as monitored by Annexin V binding in whole blood

It is important in the laboratory to develop techniques to preserve leucocyte viability in blood specimens for subsequent flow cytometric analysis. This article describes a new simple whole blood lysis method using Annexin V FITC staining which can be used to define both early and late apoptosis of granulocytes in heterogeneous cell populations, without the need for additional stains or to purify the cells (which may result in loss of the cells of interest). The differential Annexin V binding assay was in good agreement with the light microscopy reference method and showed excellent correlation with 7-aminoactinomycin D (7-AAD) staining. It was not affected by problems of morphological interpretation and artifactal changes of granulocyte deformability noted using light microscopy, or the technical difficulties encountered due to red cell contamination using the 7-AAD method. Using this new differential Annexin V staining method, we determined the optimum conditions that maintain granulocyte viability for subsequent flow cytometric analysis and are now employed in our laboratory. These conditions were lithium heparin (Hep) anticoagulated whole blood specimens kept at 4 degrees C with the addition of nutrient medium. Specimens that are anticoagulated with acid citrate dextrose (ACD) or ethyl-diacetyl-tetraacetic acid (EDTA) should also be treated similarly to preserve granulocyte viability and to overcome problems associated with identification of cell populations by flow cytometry.

SLP-76 Expression Is Restricted to Hemopoietic Cells of Monocyte, Granulocyte, and T Lymphocyte Lineage and Is Regulated During T Cell Maturation and Activation

The leukocyte-specific adapter protein SLP-76 is known to augment the transcriptional activity of nuclear factor of activated T cells and AP-1 following TCR ligation. A role for SLP-76 in additional receptor-mediated signaling events is less clear. To define the pattern of SLP-76 expression during murine hemopoiesis, we stained cells isolated from various tissues with a combination of surface markers followed by intracellular staining with a fluorochrome-labeled SLP-76-specific Ab. In the bone marrow, SLP-76 expression is largely restricted to cells of granulocyte and monocyte lineage. Heterogeneous SLP-76 expression is first detected in the CD44+CD25− subset within the CD3−CD4−CD8− thymocyte population. Interestingly, SLP-76 expression increases as thymocyte maturation progresses within the CD4−CD8− compartment but decreases as cells mature to a CD4+CD8+ phenotype. SLP-76 expression is then up-regulated following selection and concomitant with maturation to a CD4+ or CD8+ phenotype. In the periphery, SLP-76 is expressed in T lymphocytes with no detectable expression in the B cell compartment. Exposure to the superantigen staphylococcal enterotoxin B augments SLP-76 expression in the reactive T cell subset. Furthermore, in vitro stimulation with TCR-specific Abs augments the existing levels of SLP-76. These data reveal that SLP-76 expression is coordinately regulated with surface expression of a pre-TCR or mature TCR complex during thymocyte development and that TCR ligation elicits signals that result in increased expression of SLP-76.

A fast kinetic method for assessing mitochondrial membrane potential in isolated hepatocytes with rhodamine 123 and flow cytometry

Rhodamine 123 (Rh123) is widely used as a flow cytometric probe for mitochondrial membrane potential (MMP) in metabolic, pharmacologic, and toxicological studies. However, the use of relatively high concentrations of Rh123 (up to 10 micrograms/ml) and prolonged incubation times (up to 1 h), including washing steps, may be inconvenient for certain applications in which labile cells are used or which demand rapid or repeated analysis. In this paper we describe a rapid kinetic assay of MMP in isolated rat hepatocytes, based upon the quantitation of the initial rate of Rh123 uptake by living cells, selected by their scattering properties. The results indicate that at an appropriate dye-to-cell ratio (in our experiments, 50 ng Rh123/ml for 250,000-300,000 cells/ml), the initial rate of Rh123 uptake is a highly reproducible and sensitive parameter for estimation of MMP, as demonstrated by the effects of substrates and inhibitors of the glycolytic pathway and mitochondrial respiration. Because of its simplicity, rapidity (about 5 min) and metabolic implications, this assay would be also suitable for the routine evaluation of metabolic state of cell suspensions, as a complementary test to the standard dual-staining tests of viability. Other possible applications in screening pharmacologic and toxicological analysis are discussed.