Michael R. Loken

Quantitative Comparison of Myeloid Antigens on Five Lineages of Mature Peripheral Blood Cells

Five‐dimensional flow cytometry was used to identify the 5 lineages of peripheral blood leukocytes simultaneously in a single cell preparation. This technique was then used to compare quantitatively the distribution of cell surface antigens on each of these lineages of cells. Neutrophils, eosinophils, basophils, lymphocytes, and monocytes were uniquely identified by correlating their forward and orthogonal light scattering signals with the amount of cell surface‐bound IgE. These three cellular characteristics were combined with two additional immunofluorescence labels to create a 5‐dimensional space in which each leukocyte population occupied a unique position. The relative quantities of antigens on each cell type were determined for the monoclonal antibodies CD11b, CD13, CD14, CD15, CD16, CD33, CD38, CD45, CD45R, anti‐HLA‐DR, and anti‐Leu‐8 labeled with either fluorescein or phycoerythrin. The amount of antigen was described by the mean fluorescence intensity in comparison with the background fluorescence of each cell type. The distribution of the different cell surface antigens on the 5 major leukocyte populations as well as their interdonor variation were then correlated for 10 normal donors. Since none of the antigens studied was lineage specific, it was shown that the different lineages of blood cells could clearly be identified by quantitative comparison of the antigens. This study provides the basis for discrimination between mature cells and immature stages of differentiation of leukocytes and for distinction between normal and leukemic cells.

A rapid sample preparation technique for flow cytometric analysis of immunofluorescence allowing absolute enumeration of cell subpopulations

A simple and rapid method was developed for immunofluorescence measurements of cells by flow cytometry which does not require washing procedures, permitting absolute enumeration of cell subpopulations. Peripheral blood cells were labeled with fluorescein and phycoerythrin conjugated monoclonal antibodies and the nucleic acid stain LDS-751. Distilled water was added following incubation to induce erythrocyte lysis by hypotonic shock. After lysis for 30 s the tonicity of the sample was increased followed by measurement on the flow cytometer. The leukocyte populations were clearly resolved in the correlation of forward and orthogonal light scattering. The immunofluorescence resolution of the labeled leukocytes was equivalent to NH4Cl and a commercial lysing preparation. Absolute number of leukocytes and percentage of leukocyte subpopulations determined with this procedure correlated well with the results obtained with a clinical hematology analyzer. Cell recovery and preservation of cellular characteristics of three different procedures for lysing the human erythrocytes were compared. The LDS-751 permitted the discrimination of intact cells from residual erythrocyte ghosts, platelets and damaged nucleated cells. A considerable loss of cells was found for both NH4Cl and commercial lysing solution; the samples prepared by NH4Cl lysing had a selective loss of lymphocyte subpopulations as compared with the other two techniques. In contrast to the two procedures in which multiple washing steps are involved, the no wash, hypotonic lysis procedure provided a means of obtaining absolute numbers of leukocyte subpopulations identified by combining light scattering and immunofluorescence characteristics with no centrifugation steps required.

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)

Flt3 ligand promotes engraftment of allogeneic hematopoietic stem cells without significant graft-versus-host disease

Background. Graft-versus-host (GVH) reactions contribute to stable engraftment of allogeneic hematopoietic stem cell transplants. It was hypothesized that the in vivo expansion of recipient dendritic cells (DC) with the administration of ligand for Flt3 (FL) could promote allogeneic engraftment after reduced-intensity conditioning by enhancing the GVH effect. Methods. FL was first administered to three nonirradiated healthy dogs for 13 days at a dosage of 100 &mgr;g/kg/day. Next, nine dogs received 4.5 Gy total-body irradiation (TBI) and unmodified marrow grafts from dog leukocyte antigen (DLA)-identical littermates without posttransplant immunosuppression. FL was administered to the recipients at a dosage of 100 &mgr;g/kg/day from day −7 until day +5. Results. In normal dogs, FL produced significant increases in monocytes (CD14+) and neutrophils in the peripheral blood, a marked increase in CD1c+ cells with DC-type morphology in lymph nodes, and increased alloreactivity of third-party responders to peripheral blood mononuclear cells in mixed lymphocyte reactions (P <0.001). Sustained engraftment was observed in eight of nine (89%) FL-treated dogs compared with 14 of 37 (38%) controls (P =0.02, logistic regression). All engrafted FL-treated dogs became stable complete (n=2) or mixed (n=6) hematopoietic chimeras without significant graft-versus-host disease (GVHD). Recipient chimeric dogs (n=4) were tolerant to skin transplants from their marrow donors but rejected skin grafts from unrelated dogs within 7 to 9 days (median, 8 days). Conclusions. In this study, the authors showed that FL administered to recipients promotes stable engraftment of allogeneic marrow from DLA-identical littermates after 4.5 Gy TBI without significant GVHD.

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.