Biomedical subjects

J G Bender

Publications and source records attributed to J G Bender.

At least 55 records · Page 3Linked to original sources

PubMed1992

Reduced oxygen tension increases hematopoiesis in long-term culture of human stem and progenitor cells from cord blood and bone marrow.

Growth of hematopoietic stem and progenitor cells found in the mononuclear cell (MNC) fraction of human cord blood and bone marrow was evaluated under atmospheres containing reduced (5%) and normal (20%) oxygen tension. Cord blood MNC were grown in suspension and on preestablished irradiated bone marrow stromal layers, whereas bone marrow MNC were used to initiate one-step long-term bone marrow cultures (LTBMC). Reduced oxygen tension resulted in a substantial increase in both the number and frequency of colony-forming cells observed in all three types of long-term hematopoietic cultures (LTHC) studied. At various time points under low oxygen, progenitor cell numbers were as much as 12-fold, 3-fold, and 4-fold higher for granulocyte-macrophage colony-forming units (CFU-GM), erythroid burst-forming units (BFU-E), and granulocyte erythrocyte macrophage megakaryocyte colony-forming units (CFU-GEMM), respectively. In addition to these numerical increases, progenitor cells were maintained for 1-2 weeks longer under low oxygen conditions. Reduced oxygen tension also increased total cell numbers by as much as fivefold in cord blood suspension cultures, but this effect on total cell numbers was less pronounced in cultures containing a stromal layer. The rate of irradiated stromal layer degeneration, as judged by cell counts and microscopic examination, was reduced under low oxygen. Finally, the beneficial effect of reduced oxygen was comparable to the effect of an irradiated stromal layer for maintaining cord blood progenitor cells in LTHC. These results indicate that low oxygen, which better approximates the in vivo environment, enhances the growth and maintenance of both stromal and progenitor cells for a longer period of time in vitro.

Bone Marrow↗

PubMed1991

Identification and comparison of CD34-positive cells and their subpopulations from normal peripheral blood and bone marrow using multicolor flow cytometry.

Four-color flow cytometry was used with a cocktail of antibodies to identify and isolate CD34+ hematopoietic progenitors from normal human peripheral blood (PB) and bone marrow (BM). Mature cells that did not contain colony forming cells were resolved from immature cells using antibodies for T lymphocytes (CD3), B lymphocytes (CD20), monocytes (CD14), and granulocytes (CD11b). Immature cells were subdivided based on the expression of antigens found on hematopoietic progenitors (CD34, HLA-DR, CD33, CD19, CD45, CD71, CD10, and CD7). CD34+ cells were present in the circulation in about one-tenth the concentration of BM (0.2% v 1.8%) and had a different spectrum of antigen expression. A higher proportion of PB-CD34+ cells expressed the CD33 myeloid antigen (84% v 43%) and expressed higher levels of the pan leukocyte antigen CD45 than BM-CD34+ cells. Only a small fraction of PB-CD34+ cells expressed CD71 (transferrin receptors) (17%) while 94% of BM-CD34+ expressed CD71+. The proportion of PB-CD34+ cells expressing the B-cell antigens CD19 (10%) and CD10 (3%) was not significantly different from BM-CD34+ cells (14% and 17%, respectively). Few CD34+ cells in BM (2.7%) or PB (7%) expressed the T-cell antigen CD7. CD34+ cells were found to be predominantly HLA-DR+, with a wide range of intensity. These studies show that CD34+ cells and their subsets can be identified in normal PB and that the relative frequency of these cells and their subpopulations differs in PB versus BM.

Adult↗

PubMed1991

Gelatin sponge model of effector recruitment: tumoricidal activity of adherent and non-adherent lymphokine-activated killer cells after culture in interleukin-2.

This study examined the specific tumoricidal activity of lymphokine-activated killer (LAK) cells derived from tumor-infiltrating lymphocytes that prevent the growth of secondary tumors in animals harboring progressing primary tumors. A pre-implanted gelatin sponge was employed to capture infiltrating host effectors during the expression of concomitant tumor immunity. Additionally, this study compared the cytolytic activity of these sponge-derived cells with those of counterpart splenic lymphocytes. The cells from both sources were cultured for 4 days in IL-2 to generate LAK cells which were further expanded in IL-2-containing medium for up to 11 days. The cytotoxic activities of these cells were measured in a Chromium-51 release assay. The data revealed that the culture of splenic, or sponge-derived lymphocytes results in the emergence of non-adherent and adherent cell populations with LAK activity. The 4-day sponge-derived LAK cells (adherent and non-adherent) exhibited significant cytolysis of EMT6 cells while the spleen-derived counterparts showed minimal cytotoxicity toward these targets. Some NK activity in LAK cells derived from both sources was evident by their lysis of YAC-1 cells. LAK cells from both sources were incapable of lysing histo-compatible EL-4 (H-2b) tumor cells. The lysis of the EMT6 cells by the sponge-derived LAK cells was maintained over an 11-day period of culture in IL-2. Conversely, the spleen-derived LAK cells were unable to significantly lyse EMT6 cells during this period of in vitro culture. These results show the superior specific tumoricidal activity of LAK cells derived from lymphocytes mediating tumor rejection in vivo (sponge-derived) over that of counterpart splenic lymphocytes.

Animals↗

PubMed1990

Regulation of C5a and formyl peptide receptor expression on human polymorphonuclear leukocytes.

Fluorescein conjugates of C5a (FL-C5a) and formyl methionine-leucine-phenylalanine-lysine (FL-FMLPL) have been used to determine how the expression of receptors for these peptides is regulated on human polymorphonuclear leukocytes (PMN). Video intensification microscopy showed that receptors for FL-C5a were homogeneously distributed on the surface of the PMN, but within minutes were mobilized into patches and internalized by the PMN. Internalization of C5a receptors was confirmed in studies in which external FL-C5a fluorescence was quenched by reducing the pH. A similar rapid internalization was observed with FL-FMLPL. This process was inhibited for both fluorescent ligands by monensin. Reexpression of C5a and formyl peptide receptors after internalization occurred with both receptors. By comparison, the rate of reexpression of formyl peptide receptors was much faster than that observed with C5a receptors with the half maximal reexpression time for each being 5 to 10 min and 18 to 60 min, respectively. C5a receptor reexpression was completely blocked by monensin suggesting receptor recycling, whereas monensin had little effect on FMLPL receptor reexpression. The reexpression of both receptors occurred in the presence of cycloheximide indicating that this process occurred independent of protein synthesis. Additional studies on formyl peptide receptor showed that when PMN were treated with ionomycin to fully mobilize the intracellular pool of FMLPL receptors, receptor reexpression failed to occur. These studies show that both C5a and formyl peptide receptors are internalized after binding ligand, but that their reexpression occurs through different mechanisms. C5a receptors appear to be recycled to the cell surface whereas formyl peptide receptors are reexpressed predominantly by translocation from an intracellular pool.

Cell Compartmentation↗

PubMed1990

Relationship of chemotactic receptors for formyl peptide and C5a to CR1, CR3, and Fc receptors on human neutrophils.

The co-expression of C5a and formyl-methionine-leucine-phenylalanine-lysine (FMLPL) receptors with CR1, CR3, and Fc receptors on human neutrophils (PMN) was studied. Fluorescein-conjugated C5a (FL-C5a) and FMLPL (FL-FMLPL) were used to identify C5a and formyl peptide receptors. CR1, CR3, and Fc receptors were identified with monoclonal antibodies and a Texas red-labeled goat anti-mouse immunoglobulin second step reagent. The co-expression of chemotactic receptors with CR1, CR3, or Fc receptors was evaluated using two-color flow cytometry. A direct correlation between the degree of expression of receptors for FL-FMLPL and the expression of CR3, CR1, and Fc receptors on individual PMN was observed. In contrast, no correlation between the degree of C5a receptor expression and CR1, CR3, or Fc receptor expression was found. Similar results were obtained with PMN after up regulation of CR1, CR3, Fc, and FMLPL receptors by incubation at 37 degrees C for 10 min with or without phorbol myristate acetate. These data suggest that the expression of FMLPL, CR1, CR3, and Fc receptors are regulated in a similar manner, whereas C5a receptor expression is regulated independently. Furthermore, these data indicate that within a given population of PMN, a parallel exists between the degree of CR1, CR3, FMLPL, and Fc receptor expression on individual cells.

Antibodies, Monoclonal↗

PubMed1990

13-cis retinoic acid augments the production of macrophages in mouse bone marrow cultures stimulated with interleukin 3.

Mouse bone marrow cells in liquid culture with interleukin 3 generate nonadherent granulocytes, mast cells, and macrophages. The addition of 13-cis retinoic acid (13cRA) (10(-8)-10(-6) M) enhanced proliferation of the nonadherent cells, and concentrations greater than 5 x 10(-7) M stimulated a sixfold increase in adherent macrophages. Four-color flow cytometry was used to identify the lineages present using the following antibodies: MAC1 (granulocytes and macrophages), F4/80 (macrophages), B54.2 (mast cells), and H12 (anti-Thy1.2 to identify myeloid precursors). This analysis demonstrated a twofold increase in MAC1+ F4/80+ cells, which were sorted and identified morphologically as macrophages. 13cRA also increased by 60%-95% the numbers of colony-forming cells responsive to interleukin 3 (IL-3) and macrophage colony-stimulating factor (M-CSF) but did not significantly change the colony-forming cells responsive to granulocyte-macrophage colony-stimulating factor (GM-CSF). These data suggest that 13cRA increases the production of macrophages by modulating the commitment of IL-3-expanded progenitor cells to the macrophage lineage.

Animals↗

PubMed1989

Decreased opsonic activity for Staphylococcus aureus in neonatal and late gestation maternal sera.

Heat-killed Staphylococcus aureus (ATCC strain 25923) and Escherichia coli K-12 were used as target microorganisms for opsonization by serum from neonates or mothers at various stages of pregnancy or postpartum. The level of opsonic activity was evaluated by titrating serum for the ability to coat bacteria for recognition by normal human PMN. Recognition of the organisms was quantitated by measuring the PMN superoxide anion generation response to opsonized organisms. Studies show that opsonic activity for S. aureus was markedly decreased in serum from mothers in their second and third trimesters of pregnancy, in cord blood, and from infants at two weeks of age. Decreased activity was not observed in maternal serum in the first trimester of pregnancy and returned to control levels shortly after delivery. No significant difference was seen in opsonic activity for E. coli in these sera. The reduction in serum opsonic activity in mothers during the second and third trimesters of pregnancy suggests a systemic suppression of maternal immune responses during fetal development. This decreased activity is also observed in neonatal sera.

Escherichia coli↗

PubMed1988

Characterization of granulocytes and mast cells in cultures of mouse bone marrow stimulated with interleukin-3.

Bone marrow cells in liquid culture with interleukin 3 produce a population of non-adherent granulocytes and mast cells. Flow cytometry was used to identify granulocytes and mast cells on the basis of the physical properties of perpendicular light scatter (PLS) and coulter volume (CV) as well as the expression IgE and CR3 receptors. Multicolor analysis indicated there were subpopulations of Thy1.2 positive cells which transiently appeared in these cultures and also expressed IgE receptors, CR3 receptors or neither of these receptors. The data suggested a differentiation scheme in which Thy1.2 positive precursor cells give rise to granulocytes and mast cells. Further evidence for this differentiation scheme was provided from CV vs. PLS distributions which showed increases in CV and PLS as Thy1.2 positive cells differentiated into mast cells and decreases in CV and PLS as Thy1.2 positive cells differentiated into granulocytes.

Animals↗

PubMed1987

Independent regulation of human neutrophil chemotactic receptors after activation.

The fluoresceinated chemotactic factors, C5a, formyl-methionyl-leucyl-phenylalanyl-lysine (FMLPL), and casein were used in conjunction with flow cytometry to examine chemotactic factor receptor expression on polymorphonuclear leukocytes (PMN) activated with phorbol myristate acetate (PMA), C5a, or formyl-methionyl-leucyl-phenylalanine. Activation with PMA resulted in a dose-dependent increase in binding of fluorescein-labeled (FL)-casein and (FL-FMLPL) over the range of PMA concentrations from 0.5 to 50 ng/ml. In contrast, activation of PMN with PMA resulted in a dose-dependent decrease in FL-C5a binding, and activation with concentrations above 5 ng/ml resulted in a complete loss of binding. This loss of binding was not caused by inactivation of the ligand or prevented by the addition of superoxide dismutase and catalase or protease inhibitors. Furthermore, incubation of PMN with supernatants from PMN stimulated to degranulate did not reduce the availability of C5a receptors. This pattern of increased FMLPL and casein binding with decreased C5a binding was also observed with cytochalasin B-pretreated PMN that were stimulated with chemotactic factors. Parallel studies of superoxide anion generation demonstrated that PMA-treated PMN were still responsive to formyl-methionyl-leucyl-phenylalanine, but not to C5a. These data demonstrate that the activation of PMN up-regulates formyl peptide and casein receptors whereas C5a receptors are down-regulated under similar conditions.

Caseins↗

PubMed1987

Regulation of myelopoiesis.

Myeloid cells are produced by the bone marrow from stem cells and progenitor cells. This review summarizes the current understanding of how this process is regulated. Regulation of progenitor cell proliferation and differentiation occurs in microenvironments present within the bone marrow as well as on the systemic level by the release of regulators into the circulation. The regulators of central importance to myelopoiesis are growth factors necessary for the proliferation and differentiation of progenitors. These growth factors have recently been characterized and studies indicate that there is a hierarchy of factors acting upon successive differentiation stages of progenitors. Endotoxin appears to be a major modulator of myeloid growth factor production. Other inhibitors of myelopoiesis are also discussed. Regulation of myelopoiesis therefore involves a balance between growth factor production and inhibition by other factors.

Animals↗

PubMed1987

Correlation of serum opsonic activity in cystic fibrosis with colonization and disease state: measurement of opsonins to Pseudomonas aeruginosa by neutrophil superoxide anion generation.

Serum from patients with cystic fibrosis and normal controls was used to opsonize mucoid and nonmucoid Pseudomonas aeruginosa particles. Opsonic activity was then determined by measuring the production of superoxide anion (O2-) from normal neutrophils stimulated with the opsonized particles. Without any opsonization, mucoid P. aeruginosa stimulated significantly more O2- than nonmucoid P. aeruginosa. Responses to nonmucoid P. aeruginosa observed with heat-inactivated serum from patients with cystic fibrosis were significantly higher (p = 0.008) than those observed with heat-inactivated control sera. Comparisons made between patients who were colonized with P. aeruginosa and those who were not showed that heat activated serum from colonized patients had significantly higher levels of opsonic activity than heat inactivated serum from patients who were not colonized. These differences were observed with either mucoid or nonmucoid P. aeruginosa. A negative correlation was also observed between opsonic activity and clinical status measured by Schwachman scores of colonized patients. These data indicate that in patients colonized with P. aeruginosa the deterioration of their clinical status correlated with increased opsonic activity reflected in the oxidative burst response of neutrophils.

Adolescent↗

PubMed1986

A model for the regulation of myelopoiesis by specific factors.

Hematopoietic cells originate from stem cells that generate progenitor cells programmed to differentiate along specific cell lineages. Recently, a number of factors have been identified that are involved in regulating the proliferation of myeloid lineage cells. We propose a model in which a hierarchy of specific factors acts sequentially during defined stages of maturation to regulate myelopoiesis. The role of these factors as competence or progression factors in causing cells to enter and traverse the cell cycle is discussed. Experimental evidence supports the model.

Animals↗

PubMed1986

Altered function of synovial fluid granulocytes in patients with acute inflammatory arthritis: evidence for activation of neutrophils and its mediation by a factor present in synovial fluid.

In rheumatoid arthritis (RA) a chronic inflammatory state exists in which the synovial fluid is periodically filled with large numbers of polymorphonuclear leukocytes (PMNs). Oxygen radicals produced by these cells have been implicated as mediators of tissue damage and may be directly involved in the pathogenesis of RA. We examined the production of oxygen radicals by synovial fluid PMNs (SF-PMNs) and peripheral blood PMNs (PB-PMNs) by measuring chemiluminescence (CL) as well as superoxide anion (O2-) release. Increased spontaneous CL in the presence of luminol and increased CL in response to phorbol myristate acetate (PMA) was observed in SF-PMNs when compared to PB-PMNs. When zymosan was used as the stimulus in the absence of luminol, a slightly lower CL response was observed in SF-PMNs as compared to PB-PMNs. No significant differences were observed in the generation of O2- generation with any stimulus. Preincubation of normal PB-PMNs in 10% synovial fluid enhanced the luminol-dependent spontaneous and PMA-stimulated CL as well as zymosan-stimulated CL. When O2- release from normal PB-PMNs pretreated with 10% synovial fluid was compared to untreated controls, enhancement of spontaneous O2- release was observed. PMA- and zymosan-stimulated responses did not differ significantly from controls. Increased spontaneous and PMA-stimulated release of myeloperoxidase (MPO) was also observed in normal PB-PMNs pretreated with synovial fluid. These findings may explain the increased luminol-dependent CL since this type of CL requires the presence of MPO. Our findings suggest that the enhanced chemiluminescence observed in normal PMNs treated with synovial fluids may be related to increases in spontaneous O2- generation and myeloperoxidase release. Increased MPO release may account for enhanced CL observed in SF-PMNs.

Acute Disease↗

PubMed1985

Modulation of neutrophil-reduced pyridine nucleotide content following stimulation with phorbol myristate acetate and chemotactic factors.

Modulation of NAD(P)H in human neutrophils (PMN) following stimulation with phorbol myristate acetate (PMA) or chemotactic factors was determined by flow cytometry. Stimulation of PMN with 1 microgram/ml of PMA results in a time-dependent decrease in fluorescence, attributable to the oxidation of NAD(P)H. The decrease in fluorescence did not occur with PMN from a patient with chronic granulomatous disease (CGD) and was observed in only half of PMN from the mother of the patient. Loss of fluorescence in normal PMN was maximal following 7-15 min of stimulation with PMA. Simultaneous measurement of PMA-stimulated NAD(P)H oxidation and H2O2 production showed that NAD(P)H oxidation occurred as an all-or-none response while H2O2 production showed a graded response. These data suggest that with PMA stimulation, a threshold exists beyond which constitutive NAD(P)+ reduction is suppressed and complete oxidation of NAD(P)H occurs, while H2O2 production is proportional to the concentration of PMA. PMA-stimulated oxidation of NAD(P)H was reversible, and fluorescence returned to the initial level or higher after 40-60 min. Oxidation of NAD(P)H also occurred when cytochalasin B-treated PMN were stimulated with 25 nM C5a or 100 nM formyl-methionyl-leucyl-phenylalanine (f-MLP), but occurred more rapidly, peaking at 1 to 3 min. Fluorescence also returned by 5-6 min. This response to C5a and f-MLP was graded and proportional to the concentration of chemotactic factor used. Comparative studies showed that the cytochalasin-B treatment was essential for measurement of NAD(P)H oxidation, in response to C5a and F-MLP.

Complement C5↗

PubMed1985

Characterization of human mononuclear cells using reduced pyridine nucleotide fluorescence and flow cytometry.

Peripheral blood monocytes undergo an oxidative burst similar to that seen in neutrophils. The basis for this response appears to be an NAD(P)H oxidase that utilizes reduced NAD(P)H to form superoxide anion. We utilized the unique UV-stimulated fluorescence property of reduced pyridine nucleotides to analyze NAD(P)H utilization in monocytes. UV-stimulated fluorescence in mononuclear cell preparations indicated two populations of cells with the highly fluorescent cells having a Coulter volume consistent with that of monocytes. Dual laser analysis with monoclonal antibodies confirmed that these highly fluorescent cells are monocytes by showing them to be OKM1+, Leu DR+, and anti-monocyte 0.2+. Natural killer (NK) cells, as defined by Leu 7, were not found in this highly fluorescent population. Stimulation of mononuclear cells with phorbol myristate acetate caused a fluorescence loss indicative of NAD(P)H oxidation in monocytes but not in lymphocytes. Stimulation with suboptimal concentrations of PMA (1-5 ng/ml) resulted in a dose-dependent fluorescence loss in monocytes that occurred in an all-or-none fashion identical to the pattern observed in neutrophils. Simultaneous measurement of H2O2 production using dichlorofluorescein formation with NAD(P)H fluorescence indicates that oxidant production occurs in a graded manner. This method, then, provides a convenient way to study in single cells the metabolic events involved in depletion and replenishment of NAD(P)H during the oxidative burst and demonstrates an additional means by which to distinguish monocytes from lymphocytes using flow cytometry.

Antibodies, Monoclonal↗

PubMed1985

Stimulus interactions in release of superoxide anion (O2-) from human neutrophils. Further evidence for multiple pathways of activation.

A wide variety of agents stimulate superoxide anion (O2-) release from human neutrophils. To determine whether the same or different cellular pathways are utilized, neutrophils were stimulated to release O2- with combinations of f-Met-Leu-Phe (FMLP) (10(-7)M), C5a (25 nM), Con A (100 micrograms/ml), arachidonic acid (100 microM), and PMA (1 microgram/ml). These concentrations produced maximal O2- production when used alone. A synergistic response was observed when Con A was used in combination with FMLP or C5a. This response was twice the expected release in cytochalasin B-treated cells and three to five times the expected release in untreated cells. Additional studies showed that synergism was dependent upon the simultaneous presence of both agents. Additive O2- responses were observed when either FMLP, Con A, or C5a was tested in combination with arachidonic acid and when FMLP and C5a were tested together. When PMA was tested with C5a, FMLP, or Con A, a nonadditive O2- response resulted, whereas mixtures of PMA and arachidonic acid resulted in a less than additive response. These contrasting results using different soluble stimuli in combination suggest that multiple pathways exist for the stimulation of neutrophil O2- release, with some stimuli being totally independent of each other (possibly activating separate pools of oxidase), while other stimuli show cooperative effects on oxidase activation.

Adult↗

PubMed1985

Inhibition of human neutrophil function by 6-aminonicotinamide: the role of the hexose monophosphate shunt in cell activation.

Stimulation of polymorphonuclear leukocytes with phorbol myristate acetate (PMA) or chemotactic factors such as f-Met-Leu-Phe (fMLP) activates a membrane oxidase which results in the generation of the superoxide anion (O2-) and the oxidation of NADPH to NADP+. The subsequent reduction of NADP+ to NADPH is believed to be directly dependent upon activation of the hexose monophosphate shunt (HMPS). To further understand the role of the HMPS in the oxidative burst, we examined the kinetics of HMPS activation by fMLP and PMA. Both of these agents stimulate an increase in HMPS activity that parallels their production of O2-. To examine the role of the HMPS in cell activation, we treated polymorphonuclear leukocytes with the specific HMPS inhibitor, 6-aminonicotinamide. This pretreatment inhibited fMLP- and PMA-stimulated HMPS activity and O2- release by 80% and 60% respectively with a 50% inhibitory dose (ID50) of 5 X l0(-7)M. Measurement of reduced NADPH using 350 nm ultraviolet light-stimulated fluorescence and flow cytometry indicated that 6-aminonicotinamide had no effect on resting levels of NADPH fluorescence but significant inhibited the fluorescence recovery following stimulation with fMLP or PMA. In contrast, PMA- and fMLP-stimulated membrane depolarization measured with the carbocyanine dye 3,3'-dihexyloxacarbocyanine iodide and chemotaxis to fMLP were unaffected by 6-aminonicotinamide treatment. On the contrary, fMLP- or PMA-stimulated myeloperoxidase release by fMLP or PMA was enhanced by 30% and 150%, respectively, following treatment with 6-aminonicotinamide, suggesting a decreased oxidative inactivation of myeloperoxidase.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemotaxis↗

PubMed1983

Analysis of the bimodal chemiluminescence pattern stimulated in human neutrophils by chemotactic factors.

Chemotactic factors, which are important in attracting neutrophils to inflammatory sites, have also been shown to stimulate oxidative metabolism, resulting in increased chemiluminescence and release of superoxide anion (O2-). We observed a unique bimodal chemiluminescence pattern upon stimulation with either the complement-derived factor C5a or formyl-methionyl-leucyl-phenylalanine. A sharp peak of activity occurred within 1 to 2 min, and a second more extended peak was seen between 3 and 6 min. Enhancement of both peaks occurred when the cells were pretreated with cytochalasin B. Expression of both peaks was found to be related to cell density, and expression of the second peak was not dependent upon extracellular metabolites released during the first peak. Cells preincubated in luminol and then thoroughly washed responded with only a single peak coincident with the second peak. Together these findings indicate that the first peak is extracellular in origin, whereas the second peak is cell associated. Studies with scavengers of oxygen intermediates and inhibitors of myeloperoxidase for the oxidation of luminol, which may occur in part through the formation of HOCl as well as through a non-HOCl-mediated mechanism. Evidence for a non-HOCl-mediated mechanism comes from experiments in which luminol, myeloperoxidase, and O2- generated by xanthine-xanthine oxidase produce luminescence in the absence of chloride ion. These studies provide further insight into the sequence of events which occur during the stimulation of neutrophils with chemotactic factors and the nature of neutrophil chemiluminescence.

Blood Cell Count↗