Biomedical subjects

M R Loken

Publications and source records attributed to M R Loken.

At least 55 records · Page 3Linked to original sources

PubMed1988

Flow cytometric analysis of normal B lymphoid development.

Identification of the antigens expressed on marrow B lineage cells can be used to develop a model for the sequential acquisition of cell surface antigens during B lymphocyte development. The data suggest that the surface antigen expression is highly controlled during the development of B cells with the coordinated acquisition of multiple cell surface antigens during the maturational process. The developmental scheme in figure 6 is inferred from the expression of cell surface antigens on single samples. Confirmation of the progression from one stage to the next requires the isolation of a particular stage with subsequent induction to the next stage in-vitro. These data suggest that the development of B lymphoid cells may be discrete rather than continuous. The most immature cells identifiable in the bone marrow express CD34+ as well as HLA-DR. The earliest recognizable B lineage cells (CD19+, bright CD10+) also express CD34+. These cells are smaller by forward light scattering when compared to the cells which express only CD34+ (precursor of myeloid cells). Cells within stage I also express TdT in the nucleus and are proliferating. As the cells progress from stage I to stage II, the B lineage cells lose cell surface CD34 and nuclear TdT. At this time the density of HLA-DR and CD45 increases while the amount of CD10 decreases. These changes occur with no detectable change in cell size as assessed by forward light scattering. HLA-DP is first detected on the cells at this time. The progression of cells from stage II to stage III is marked by the acquisition of CD20, HLA-DQ, and sIgM. The amount of CD45 increases further in the transition between stage II and stage III. The acquisition CD21 and CD22 as well as the loss of CD10 distinguishes stage IV from stage III. Once the cellular composition of normal marrow has been defined, perturbations from homeostasis can be identified. Since marrow is the tissue most sensitive to injury by most antineoplastic chemotherapy and radiotherapy regimens, a means of quantifying the changes from the normal state can provide an assessment of the cytotoxic injury produced in individual patients. By monitoring the return to normal, it may be possible to more precisely individualize therapy for each patient. With a clear understanding of normal hematopoiesis, it should also be possible to identify maturational blocks which occur in hypoplastic marrow states. This may provide a means of identifying the regulatory points for each lineage and provide strategies for overcoming the inhibition of development.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗

PubMed1988

Assessment of proliferation during maturation of the B lymphoid lineage in normal human bone marrow.

Different stages of B lymphoid maturation were identified in normal bone marrow using multiple cell surface markers. The proliferation status of each of these maturational stages was determined by simultaneous quantitative DNA analysis on a flow cytometer. The technique used to quantify these parameters preserved the cell surface immunofluorescence, the light scattering properties and the stoichiometric binding to DNA. The proliferating cells were confined to a distinct population of cells expressing CD10. The number of proliferating cells in these populations was relatively constant among 12 separate bone marrow samples. The data suggest that the timing and rate of proliferation of cells within a single lineage may be a preprogrammed aspect of normal maturation.

Antibodies, Monoclonal↗

PubMed1988

Asynchronous antigen expression in B lineage acute lymphoblastic leukemia.

Cell surface phenotypes of 113 B lineage acute lymphocytic leukemia (ALL) cases, defined by the presence of HLA-DR and at least one B-cell-specific antigen (either CD19, CD20, or CD22), were compared with antigen-defined stages of normal B lymphocyte development. The cases were first evaluated for expression of HLA-DR, CD19, CD34, CD10, CD20, and CD22 by indirect one-color immunofluorescence. Pairwise comparisons of cell surface marker expression were performed for each leukemic sample: no correlations were observed for paired antigen expression on the leukemic samples using antigens expressed either early or late during normal B lymphoid development. Complete immunophenotypes of the cases were then compared with normal B-cell developmental stages. Sixteen different complete immunophenotypes were observed on the leukemias that were not found in normal marrow; at least 78% of the cases demonstrated such "asynchronous" combinations of B lymphoid-associated differentiation antigens. Several samples were subsequently studied by two-color immunofluorescence, and the presence of doubly labeled cells with "asynchronous" antigen combinations was confirmed. These results indicate that the majority of B lineage leukemias exhibit "developmental asynchrony," as compared with normal marrow B cells. The data further suggest that ALL cases do not accurately represent cells arrested at the stage where the leukemogenic event occurred. Rather, ALL appears to be a disease in which there may be maturation of leukemic blasts; but this maturation is "asynchronous" when compared with the normal developmental process.

Adult↗

PubMed1987

Comparison of helium-neon and dye lasers for the excitation of allophycocyanin.

Allophycocyanin (APC) has a broad absorption spectrum permitting several different lasers to be used to excite this dye in a flow cytometer. A comparison was made between a dye laser and a helium-neon (HeNe) laser for the excitation of APC as an immunofluorescent chromophore. The ratio of fluorescence of stained to unstained lymphocytes (signal to background) was used to assess differences in sensitivity. In determining the best wavelength for operating the dye laser, it was found that there was little difference in the ability to separate the positive-labelled cells from the unstained cells using 600 nm or 633 nm light for excitation of APC. A study of the effect of laser power on the signal to background identified a nonlinear relationship. It was found that the sensitivity obtained with 47 mW of 633 nm light from a HeNe laser was near the maximum attainable. This sensitivity was comparable to that obtained using phycoerythrin as an immunofluorescence chromophore. APC had the added advantage of being applicable to the study of highly autofluorescent cells. Exciting this chromophore using red light dramatically decreased the autofluorescence observed even on alveolar macrophages.

Animals↗

PubMed1987

Cell surface antigens on human marrow cells: dissection of hematopoietic development using monoclonal antibodies and multiparameter flow cytometry.

A single sample of bone marrow includes the entire range of the developmental process, since cells of all stages and lineages are present. By selecting appropriate monoclonal antibodies, marrow cells of different lineages can be identified, even in their immature forms. Maturationally different bone marrow cells can be distinguished on the basis of their cell surface antigen expression and physical characteristics on a flow cytometer. Antigenic markers can be used within a lineage to trace the development from colony-forming cells to functional blood cells. Changes in cellular markers are observed as smooth, quantitative increases or decreases in cellular antigen expression. After defining the composition of normal marrow, it is possible to identify perturbations from the steady state and to monitor the return to homeostasis. Cells at various stages can be enumerated, then isolated for further study. In particular, these studies provide for the identification, purification and manipulation of the earliest hematopoietic progenitor cells.

Antibodies, Monoclonal↗

PubMed1987

Coordinate glycosylation and cell surface expression of glycophorin A during normal human erythropoiesis.

The expression of two epitopes on glycophorin A (GPA) during erythroid development was examined on normal human bone marrow using quantitative flow cytometry. The highly correlated binding of two monoclonal antibodies, one sensitive and the other insensitive to glycosylation, indicated that the two epitopes were coordinately expressed during erythroid development. Both antigens reached a maximum expression during the early normoblast stage and were maintained at a constant amount per cell throughout further maturation to erythrocytes. These data suggest that glycosylation of GPA, as detected by antibodies recognizing blood group (M) and (N) antigens, does not increase during erythroid maturation.

Antibodies, Monoclonal↗

PubMed1987

Flow cytometric analysis of human bone marrow: I. Normal erythroid development.

Flow cytometry was used to identify maturational differences of erythroid lineage cells in normal human bone marrow by combining physical characteristics, the expression of multiple cell surface antigens, and nucleic acid content. Normal low-density bone marrow cells could be divided into four populations, based on forward and right-angle light scattering. Erythroid cells, at different maturational stages, were found in three of these four marrow subpopulations. The sequentially correlated expression of three cell surface markers--HLe-1, transferrin receptor, and glycophorin--allowed us to study erythroid maturation from the colony forming cell to the mature erythrocyte. HLe-1 was expressed on the earliest identifiable erythroid cells and was progressively lost as the cells matured. Transferrin receptor began to be expressed at the BFU-E stage and disappeared at the late reticulocyte stage. Transferrin receptor expression preceded glycophorin expression, the latter beginning on morphologically recognizable erythroid precursors just after the CFU-E stage. In contrast to both HLe-1 and transferrin receptor, which were progressively lost during the maturational process, once glycophorin had been maximally expressed on the cell surface, it remained at constant quantities to the mature erythrocyte stage. Although developing nucleated erythroid cells at approximately the normoblast stage had light-scattering properties similar to those of lymphoid cells, these two cell types could be resolved by cell surface antigen expression. Normoblasts were glycophorin positive and HLe negative, whereas lymphoid cells expressed HLe and either Leu 4, Leu 11, or Leu 12. Decreases in cellular nucleic acid content, corresponding first to the extrusion of the nucleus and second to the loss of reticulum, characterized the later stages of erythroid development. These characteristics and instrumentation can be used to purify erythroid cells at various developmental stages.

Antibodies, Monoclonal↗

PubMed1987

Antigenic analysis of hematopoiesis. VI. Flow cytometric characterization of My-10-positive progenitor cells in normal human bone marrow.

We have previously shown [1] that the anti-My-10 murine monoclonal antibody detected an epitope of a 115-kDa glycoprotein expressed specifically on KG-1a leukemia cells and a small subset of normal human bone marrow cells. This My-10+ marrow cell subset was shown to contain a highly enriched population of morphologic blast cells and hematopoietic colony-forming cells [1]. In this report, My-10+ cells were characterized, by flow cytometry, as an approximately 1% subpopulation of normal human bone marrow cells. My-10+ cells were slightly larger than lymphocytes and agranular, as determined by their fluorescence-activating cell sorting (-er) (FACS) light-scattering properties. In two-color immunofluorescence experiments, My-10+ cells coexpressed the HLA-DR antigen. However, there was no detectable cellular coexpression of My-10 with either the Leu 1-5, 7, 9, 11, 15, M3, or My-18 antigens. There was an average of approximately 50,000 My-10 molecules per My-10+ marrow cell. This provides further evidence that the My-10 molecule is expressed, at relatively low levels, selectively on early human marrow cells but not on mature lymphohematopoietic cells.

Antibodies, Monoclonal↗

PubMed1987

Flow cytometric analysis of human bone marrow. II. Normal B lymphocyte development.

A panel of B lymphoid-reactive monoclonal antibodies was used to analyze the phenotypic changes that accompany B lymphocyte development in normal human bone marrow. The B lymphoid cells were identified using light scattering and the expression of CD19 on a flow cytometer. Quantitative three-color immunofluorescence was then used to correlate other cell surface antigens on these cells identified as B lymphoid in normal marrow. CD10 and CD20 identified almost exclusive populations and provided a convenient means of discriminating between the less and more mature B lineage cells. The CD10+ cells could be further subdivided using CD34. The population of CD19+, CD10+, CD34+ cells comprised only 0.6% of marrow cells, but these contained the majority of terminal deoxynucleotidyl transferase (TdT+) cells. In the assessment of class II antigens, HLA-DR was expressed on all B lineage cells whereas HLA-DP preceded HLA-DQ in appearance during the developmental process. Among the later antigens expressed on B lineage cells, cell surface IgM, CD20, and HLA-DQ were expressed at essentially the same time. Cell surface CD10 was lost at the time when CD21 and CD22 were acquired on the cell surface. These data illustrate that multiparameter flow cytometry can be used to define a continuous progression of stages of B lymphocyte development based on cell surface antigen expression even though these cells represent a minor fraction of normal marrow cells.

Antibodies, Monoclonal↗

PubMed1986

S-phase detection with an antibody to bromodeoxyuridine. Role of DNase pretreatment.

We have previously described a monoclonal antibody (BU-1) to 5-bromo-2-deoxyuridine (BrdUrd) that is useful for measurement of cell cycle S-phase. BU-1 hybridoma supernatant reacted with incorporated BrdUrd after the cells had been ethanol fixed; without a requirement for acid or base denaturation. We have found that this reactivity is lost if purified antibody is used, if the culture supernatants are heated, or if a mycoplasma-free hybridoma line is isolated. The supernatant contained endogenous DNase activity that was a result of mycoplasma infection of the cell line. This DNase activity was required for staining the cells with BU-1 in the absence of other denaturation steps. The endogenous DNase could be substituted for by the addition of bovine pancreatic DNase I. The disruption of the double stranded DNA structure with an enzyme rather than with harsh chemical or heat treatments does not affect protein structure or cellular morphology and allows the detection of incorporated BrdUrd of morphologic or antigenic cell subsets. DNase pre-treatment may also be useful for detection of other 'hidden' DNA antigens.

Antibodies, Monoclonal↗

PubMed1986

The relationship of CD16 (Leu-11) and Leu-19 (NKH-1) antigen expression on human peripheral blood NK cells and cytotoxic T lymphocytes.

We examined the antigenic and functional characteristics of human peripheral blood lymphocytes that differentially express the CD16 (Leu-11) and Leu-19 (NKH-1) antigens. Leu-19 is a approximately 220,000 daltons protein expressed on approximately 15% of freshly isolated peripheral blood lymphocytes. Within the Leu-19+ subset, three distinct populations were identified: CD3-,CD16+,Leu-19+ cells; CD3+,CD16-,Leu-19+ cells; and CD3-,CD16-,Leu-19bright+ cells. Both the CD3+,CD16-,Leu-19+ and CD3-,CD16+,Leu-19+ populations mediated non-major histocompatibility complex (MHC)-restricted cytotoxicity against the NK-sensitive tumor cell K562 and were large granular lymphocytes. CD3-,CD16+,Leu-19+ NK cells were the most abundant (comprising approximately 10% of peripheral blood lymphocytes) and the most efficient cytotoxic effectors. The finding that CD3+,Leu 19+ lymphocytes mediated cytotoxicity against K562 unequivocally demonstrates that a unique subset of non-MHC-restricted cytotoxic CD3+ T lymphocytes are present in the peripheral blood of unprimed, normal individuals. However, CD3+,CD16-,Leu-19+ cells comprised less than 5% of peripheral blood lymphocytes, and the cytotoxic activity of this subset was significantly less than CD3-,CD16+,Leu-19+ NK cells. Most CD3+,Leu-19+ T cells co-expressed the CD2, CD8, and CD5 differentiation antigens. The antigenic and functional phenotype of peripheral blood CD3+,Leu-19+ cytotoxic T lymphocytes corresponds to the interleukin 2-dependent CD3+ cell lines that mediate non-MHC-restricted cytotoxicity against NK-sensitive tumor cell targets. A small population of Leu-19bright+ lymphocytes lacking both CD3 and CD16 was also observed. This population (comprising less than 2% of peripheral blood lymphocytes) contained both large agranular lymphocytes and large granular lymphocytes. CD3-,CD16-,Leu-19bright+ lymphocytes also mediate non-MHC-restricted cytotoxicity. The relationship of these CD3-CD16-,Leu-19bright+ lymphocytes to CD3+ T cells or CD16+ NK cells is unknown.

Animals↗

PubMed1986

T15 idiotype expression in the murine response to phosphorylcholine is actively regulated by genes linked to the Igh-C locus.

In this report, we demonstrate the existence of a regulatory system that can determine the relative expression of individual clones (idiotypes) within the total immune response to PC. Studies of Igh-C-congenic mice and backcross analysis demonstrate that this regulation is controlled by genes linked to the immunoglobulin heavy chain locus. The regulation acts in a trans fashion. The regulatory genes of one parental allele can control the expression of idiotopes coded for by both parental alleles. This regulation does not appear to affect the quantity of the response, but could affect the quality of the response, depending on the potential repertoire and avidity of the individual clones available to respond to a given antigenic challenge.

Animals↗

PubMed1986

Antigenic analysis of hematopoiesis. IV. The My-11 hematopoietic cell surface antigen is expressed by myelomonocytic and lymphoid, but not erythroid, progenitor cells.

The anti-My-11 murine monoclonal antibody reported on in this work identifies a KG-1a cell surface glycoprotein with apparent molecular mass of 210,000 daltons. Peripheral blood B-lymphocytes, and a novel subset of T-lymphocytes (not coinciding with helper or cytotoxic subsets) express My-11 antigen; granulocytes, red cells, and platelets are antigen negative. In normal bone marrow, lymphoid progenitors (TdT positive) and most granulocyte-monocyte progenitors express My-11, but erythroid and multilineage progenitors are My-11 negative. Approximately half of acute leukemia blast cell specimens are My-11 positive. The My-11 antigen distinguishes between lymphohematopoietic cells on the basis of lineage, and assists in the purification of hematopoietic progenitor cells and the subclassification of leukemias and normal lymphocytes.

Antibodies, Monoclonal↗

PubMed1985

Simultaneous analysis of cell surface antigens, bromodeoxyuridine incorporation and DNA content.

A method has been developed for correlating the presence of cell surface markers with bromodeoxyuridine (BrdUrd) uptake. We have found that paraformaldehyde fixation will maintain immunofluorescent cell surface staining through acid denaturation that is necessary for anti-BrdUrd reactivity to single-stranded DNA. In addition, the forward angle light scattering was maintained, even though the cells had been exposed to 2N HCl and detergent. The protocol was tested on three model systems: mouse thymus, a human cell line (CCRF-SB), and peripheral blood leukocytes. It was found that there was no specific loss of lymphocyte subsets.

Animals↗

PubMed1985

Two B-cell subpopulations identified by flow cytometry.

Ig+ spleen cells were analysed by light scatter analysis on a flow cytometer and two distinct subpopulations were identified. The large Ig+ cells (10-11 micron in diameter) were found in spleen and bone marrow, whereas the small Ig+ cells (7-8 micron in diameter) were found in all lymphoid tissues. Of the total Ig+ splenic lymphocytes, 40-60% were large Ig+ cells and had surface IgM, Ia and Fc gamma receptors. The large Ig+ cells were highly enriched for responsiveness to the B-cell mitogens, anti-Ig, Nocardia water-soluble mitogen and LPS, whereas the small Ig+ splenic cells had little or no responsiveness to these mitogens.

Animals↗

PubMed1984

Three-color immunofluorescence analysis of Leu antigens on human peripheral blood using two lasers on a fluorescence-activated cell sorter.

A fluorescence-activated cell sorter was modified to quantify simultaneously three immunofluorescence stains on a population of cells. A dye laser containing rhodamine 6G was used to obtain 600 nm light to excite Texas Red coupled avidin. An argon ion laser operating at 488 nm excited both fluorescein and phycoerythrin directly conjugated antibodies. The emission from these fluorophores could be independently quantified as demonstrated by the histograms generated by samples labeled separately with each of the three stains. This three-color detection system was used to analyze human peripheral blood mononuclear cells for the expression of three antigens: Leu 2, Leu 7, and Leu 11. Upon reanalysis of the list mode data, several discrete subpopulations of lymphocytes could be identified based on the quantitative expression of these three antigens. Of particular interest in the normal sample studied was a population of dimly labeled Leu 2+ cells which were predominantly Leu 11+, a phenotype which is seen infrequently in normal individuals. This technique expands the combinations of antigens that can be studied at any one time and will facilitate the detection and functional analysis of cells in heterogeneous populations.

Antibodies, Monoclonal↗

PubMed1984

Constancy of cell buoyant density for cultured murine cells.

The relationship between cell cycle and cell density was determined for three different lines of mouse cells by equilibrium centrifugation of suspension cultures. The mean cell densities of the three lines differed significantly, with values of 1.0622, 1.0678, 1.0540 gm/ml for 70Z/3, S 107, and ABE 8, respectively. However, the density distributions within each of the three lines were indistinguishable, with an average coefficient of variation about 5% of the mean reduced density (i.e., density minus one). Quantitative DNA analysis of the cells separated by density showed that the proportion of cells in G1, S, and G2 + M phase of the cell cycle changed very little or not at all with cell density. In addition, cells separated by size (and therefore by phase of the cell cycle) using velocity sedimentation had the same means and distributions of densities. These results indicate that there is little or no change in cell density as the cells traverse the life cycle and that buoyant density appears to be a constant property of a cell type.

Animals↗

PubMed1984

Quantitative fluorescence analysis of cyclosporine binding to human leukocytes.

The purpose of this investigation was to estimate the binding of cyclosporine at the single-cell level on human peripheral lymphocytes, and to test possible identity of the cyclosporine-binding site with a common receptor of T cell activation. A dansyl-coupled derivative (Dans cyclosporine) was used as a fluorescent probe. The histograms of unseparated, labeled peripheral leukocytes obtained by a fluorescence-activated cell sorter (FACS) showed that Dans cyclosporine stained all leukocytes--but two distinct populations could be separated based on the intensity of fluorescence. The more brightly labeled cells consisted mainly of granulocytes and monocytes, whereas the less-bright cells represented the lymphocyte compartment. Fluorescence microscopy revealed binding on the membrane for both cell populations; the label was, however, rapidly internalized in phagocytes. For both populations binding was saturable, time and temperature dependent, and reversible. Half-saturation occurred at approximately 5 X 10(-7) M (Kd). With respect to lymphocyte subpopulations, no difference of cellular fluorescence was found between unseparated lymphocytes and T cell subsets. In addition, mitogens such as concanavalin A, phytohemagglutinin, phorbol 12-myristate 13-acetate, or OKT3 antibody did not inhibit Dans cyclosporine binding. These results clearly indicate that cyclosporine binds to all peripheral blood lymphocytes, and no preferential binding on T cell subsets can be detected.

Adult↗