Development of the granule population in neutrophil granulocytes from human bone marrow

Validation of an integrated Raman- and angular-scattering microscopy system on heterogeneous bead mixtures and single human immune cells

A microscopy system has been constructed that is capable of simultaneously acquiring both Raman spectra and angle-resolved elastic-scattering patterns in either epi- or transillumination modes with a 7 mum spot size. The benefits and drawbacks of the epi- and transillumination modalities are discussed. Validation studies have been performed on single beads of a few micrometers in size, as well as on ensembles of submicrometer particles. In addition, transilluminated Raman and elastic-scattering spectra were obtained from single granulocytes and peripheral blood monocytes. Both the Raman- and the elastic-scattering channels show clear differences between the two types of immune cells.

Light scattering by neutrophils: model, simulation, and experiment

We studied the elastic light-scattering properties of human blood neutrophils, both experimentally and theoretically. The experimental study was performed with a scanning flow cytometer measuring the light-scattering patterns (LSPs) of individual cells over an angular range of 5-60 deg. We determined the absolute differential light-scattering cross sections of neutrophils. We also proposed an optical model for a neutrophil as a sphere filled by small spheres and prolate spheroids that correspond to granules and segmented nucleus, respectively. This model was used in simulations of LSPs using the discrete dipole approximation and different compositions of internal organelles. A comparison of experimentally measured and simulated LSPs gives a good qualitative agreement in LSP shape and quantitative agreement in overall magnitude of the differential light-scattering cross section.

Nucleobindin co-localizes and associates with cyclooxygenase (COX)-2 in human neutrophils

The inducible cyclooxygenase isoform (COX-2) is associated with inflammation, tumorigenesis, as well as with physiological events. Despite efforts deployed in order to understand the biology of this multi-faceted enzyme, much remains to be understood. Nucleobindin (Nuc), a ubiquitous Ca²⁺-binding protein, possesses a putative COX-binding domain. In this study, we investigated its expression and subcellular localization in human neutrophils, its affinity for COX-2 as well as its possible impact on PGE₂ biosynthesis. Complementary subcellular localization approaches including nitrogen cavitation coupled to Percoll fractionation, immunofluorescence, confocal and electron microscopy collectively placed Nuc, COX-2, and all of the main enzymes involved in prostanoid synthesis, in the Golgi apparatus and endoplasmic reticulum of human neutrophils. Immunoprecipitation experiments indicated a high affinity between Nuc and COX-2. Addition of human recombinant (hr) Nuc to purified hrCOX-2 dose-dependently caused an increase in PGE₂ biosynthesis in response to arachidonic acid. Co-incubation of Nuc with COX-2-expressing neutrophil lysates also increased their capacity to produce PGE₂. Moreover, neutrophil transfection with hrNuc specifically enhanced PGE₂ biosynthesis. Together, these results identify a COX-2-associated protein which may have an impact in prostanoid biosynthesis.

Single-cell optical imaging of the phagocyte NADPH oxidase

The phagocyte NADPH oxidase is a key component of the innate immune response against invading microorganisms, because the generation of superoxide (O(2)(-)) inside the phagocytic vacuole by this enzyme is responsible for microbial killing by mechanisms that are directly or indirectly dependent on reactive oxygen species (ROS) formation. Most of what is known about the membrane-embedded and cytosolic NADPH oxidase subunits and their intricate network of interactions on assembly and activation has been derived from biochemical and biophysical studies involving subcellular fractionation or reconstituted cell-free systems. Such investigations can be complemented by single-cell microscopy on phagocytes, which may reveal spatial and/or temporal details about NADPH oxidase assembly that cannot be obtained from fractionated-cell assays. In recent years, we have investigated the NADPH oxidase in neutrophils using two complementary optical imaging techniques: Raman microscopy, a vibrational spectroscopic technique that does not require protein labeling, and live-cell fluorescence microscopy, which sheds light on the dynamics of NADPH oxidase assembly in individual cells. Here, we briefly introduce these techniques, compare their characteristics, and show their potential for studying NADPH oxidase at the single-cell level. New microscopy data are presented to illustrate the versatility of Raman and fluorescence microscopy on intact neutrophils.

All-trans retinoic acid and hematopoietic growth factors regulating the growth and differentiation of blast progenitors in acute promyelocytic leukemia

Although acute leukemia is generally thought to be characterized by maturation arrest, it has been shown that differentiation occurs in blast cells of acute myelogenous leukemia (AML) in vitro as well as in vivo, and that morphologically abnormal mature polymorphonuclear neutrophils (PMNs) often seen in patients with AML are possibly derived from spontaneously differentiating leukemic cells. Acute promyelocytic leukemia (APL) is an unique example in which these features of AML are evident in an almost complete form; administration of all-trans retinoic acid (ATRA) induces differentiation of neoplastic cells into mature neutrophils and successfully induce complete remission in most patients. However, PMNs appearing during ATRA treatment are morphologically abnormal, as indicated not only by the presence of Auer rods but also by neutrophil secondary-granule deficiency that is commonly seen in AML. Moreover, ATRA has heterogeneous effects on the growth of blast progenitors in APL in different patients, being inhibitory, stimulatory or ineffective, which might account in part for the leukemia relapse in patients treated with ATRA alone. Hematopoietic growth factors regulate the growth of blast progenitors in APL. Among them, granulocyte colony-stimulating factor (G-CSF) is unique in that it preferentially stimulates clonal growth, but not self-renewal, in many APL cases, and synergistically enhances the differentiation-inducing effect of ATRA when used in combination. Many other compounds also exert such synergistic effects with ATRA, for which a variety of mechanisms have been suggested. It is crucial to precisely elucidate the functions of these molecules governing the growth/differentiation balance of AML blast progenitors and the mechanisms underlying their deregulated differentiation program in order to achieve effective differentiation therapy for patients with AML, not restricted to APL.

Neutrophil Secondary-Granule Deficiency as a Hallmark of All-Trans Retinoic Acid–Induced Differentiation of Acute Promyelocytic Leukemia Cells

Acute promyelocytic leukemia (APL) is a neoplasm with the unique chromosomal translocation t(15; 17), which involves the retinoic acid receptor α gene. All-trans retinoic acid (ATRA) has been used for APL patients as a potent therapeutic agent to induce differentiation of leukemia cells. Although polymorphonuclear leukocytes (PMNs) appearing in the blood and bone marrow during ATRA treatment often possess Auer rods, indicating their neoplastic origin, other morphological abnormalities of PMNs have not been elucidated. We studied the morphological changes of APL cells during ATRA treatment at the ultrastructural level. Although most aberrant primary granules, including Auer rods, became morphologically normal in response to ATRA therapy and the nuclei showed chromatin condensation and lobulation, resulting in the emergence of PMNs, the lobulated nuclei often had nuclear filamentous connections and/or nuclear blebs, indicating some pathological process. Furthermore, PMNs, particularly early in ATRA treatment, lacked neutrophil secondary granules as did the PMNs appearing in a culture of APL cells incubated with ATRA, findings consistent with previously reported data that acute myeloid leukemia cell lines do not produce secondary granule proteins even after induction of differentiation towards mature neutrophils. The present data indicate that ATRA is incapable of inducing complete morphological maturation of APL cells and that secondary-granule deficiency may be a hallmark of aberrantly differentiated leukemic cells.

Neutrophil Secondary-Granule Deficiency as a Hallmark of All-Trans Retinoic Acid–Induced Differentiation of Acute Promyelocytic Leukemia Cells

Acute promyelocytic leukemia (APL) is a neoplasm with the unique chromosomal translocation t(15; 17), which involves the retinoic acid receptor α gene. All-trans retinoic acid (ATRA) has been used for APL patients as a potent therapeutic agent to induce differentiation of leukemia cells. Although polymorphonuclear leukocytes (PMNs) appearing in the blood and bone marrow during ATRA treatment often possess Auer rods, indicating their neoplastic origin, other morphological abnormalities of PMNs have not been elucidated. We studied the morphological changes of APL cells during ATRA treatment at the ultrastructural level. Although most aberrant primary granules, including Auer rods, became morphologically normal in response to ATRA therapy and the nuclei showed chromatin condensation and lobulation, resulting in the emergence of PMNs, the lobulated nuclei often had nuclear filamentous connections and/or nuclear blebs, indicating some pathological process. Furthermore, PMNs, particularly early in ATRA treatment, lacked neutrophil secondary granules as did the PMNs appearing in a culture of APL cells incubated with ATRA, findings consistent with previously reported data that acute myeloid leukemia cell lines do not produce secondary granule proteins even after induction of differentiation towards mature neutrophils. The present data indicate that ATRA is incapable of inducing complete morphological maturation of APL cells and that secondary-granule deficiency may be a hallmark of aberrantly differentiated leukemic cells.

Biosynthesis, processing and sorting of neutrophil proteins: insight into neutrophil granule development

Neutrophil granulocytes are specialized phagocytic cells that carry a collection of granules for regulated secretion, each with distinct constituents. The granules can be classified as azurophil (primary), developed first, followed in time by specific (secondary) granules gelatinase granules, and secretory vesicles. Stage- and tissue-specific transcription factors govern the successive expression of genes for granule proteins to allow storage of the gene products in these organelle categories whose packaging is separated in time. Many of the granule proteins, in particular those of the heterogeneous lysosome-like azurophil granules, are subject to extensive post-translational proteolytic processing into mature proteins, most commonly as a post-sorting event. A selective aggregation of proteins destined for storage in granules, as discussed in this review, would facilitate their retention and eliminate a need for distinct sorting motifs on each granule protein. Aggregation of granule proteins, that are often cationic, would be assisted by the anionic serglycin proteoglycans present in neutrophils. The antibacterial granule proteins can serve as models for antibiotics and some of them possess a potentially useful therapeutic ability to bind and neutralize endotoxin. Because aberrant expression of transcription factors regulating the synthesis of granule proteins is often found in leukemia, the clarification of mechanisms regulating the timed expression of granule proteins will shed light on the maturation block in myeloid leukemias.

Dynamic reorganization of the alkaline phosphatase-containing compartment during chemotactic peptide stimulation of human neutrophils imaged by backscattered electrons

Scanning electron microscopy (EM) and cytochemical techniques were used to examine the alkaline phosphatase-containing compartment in human neutrophils after stimulation with nanomolar concentrations of N-formylmethionyl-leucyl-phenylalanine (10(-8) M fMLP). Alkaline phosphatase (AlkPase) activity was demonstrated with a lead-based metal capture cytochemical method. The reaction product was visualized with the backscattered electron imaging mode of scanning EM, and analyzed by electron probe X-ray microanalysis. Alkaline phosphatase activity was detected only in fMLP-stimulated neutrophils; unstimulated neutrophils displayed no activity. Stimulation of human neutrophils with 10(-8) M fMLP induced a time-dependent intracellular redistribution of irregular round or tubular granules containing alkaline phosphatase activity, as seen by backscattering. The intracellular redistribution of alkaline phosphatase activity was accompanied by increased cytochemical activity on the cell surface. The reaction product was localized preferentially on ridges and folds of polar neutrophils. Reorganization of the AlkPase-containing compartment correlated with changes induced by fMLP in cell shape, ie, membrane ruffling and front-tail polarity, as observed with the secondary electron image mode of scanning EM. These findings demonstrate the intracellular reorganization, increase, and asymmetric distribution of alkaline phosphatase activity on the plasma membrane of human neutrophils after stimulation by chemotactic peptides.

Cytochemical characterization of leucocytes from the seawater teleost, gilthead seabream (Sparus aurata L.)

The cytochemical characterization of head-kidney and peripheral blood leucocytes of gilthead seabream (Sparus aurata L.) was studied by light and electron microscopy. Neutrophilic granulocytes show some cytoplasmic granules, which are positive for alkaline phosphatase and peroxidase but acid phosphatase negative. The scarce granules found in the cytoplasm of the circulating neutrophils and their cytochemical features seem to be indicative of an immature stage. Acidophils are also alkaline phosphatase and peroxidase positive at pH 11.0. They are strongly positive for acid phosphatase and acid phosphatase activity may thus be considered a cytochemical marker to characterize and differentiate neutrophilic from acidophilic granulocytes in this fish species. Three granule populations are characterized in the cytoplasm of the gilthead seabream acidophils: the first is positive only for peroxidase and the second contains a dense core with acid and alkaline phosphatase activities, surrounded by a thin peroxidase positive electron-dense halo. The third granule type contains an eccentric core, which is strongly positive for acid and alkaline phosphatase and peroxidase. As regards their cytochemical features, the first and second granule types seem to correspond respectively to the azurophilic and specific granules found in acidophils of mammals and could be involved in phagocytic processes, thus playing an important microbicidal role in this species. The monocytes, monocyte-macrophages and macrophages show different cytochemical features. The first have scarce acid phosphatase-positive lysosomes, while blood monocyte-macrophages and macrophages are positive for acid and alkaline phosphatases and for peroxidase; the monocyte-macrophages show scarce lysosomes.

A novel intracellular compartment with unusual secretory properties in human neutrophils

Human neutrophils contain a novel intracellular compartment that is distinct from the previously characterized azurophil and specific granules. This compartment is distinguished by the presence of cytochemically detectable alkaline phosphatase activity. The alkaline phosphatase-containing compartments are short rod-shaped organelles that rapidly undergo a dramatic reorganization upon cell stimulation with either a chemoattractant or an active phorbol ester. Biochemical analysis shows that in unstimulated neutrophils the majority of the alkaline phosphatase activity is intracellular, but after stimulation essentially all of this activity becomes associated with the cell surface. The exocytotic pathway is unusual in that these small organelles fuse to form elongated tubular structures before their association with the plasmalemma.

Neutrophil function and oral disease

The pathological sequela of reduced neutrophil function in the oral cavity and the mechanisms behind dysfunction have added to our understanding of infectious diseases. Numerous examples have been given, and the overriding conclusion must be that any impairment of neutrophil function will lead to some degree of increased susceptibility to infection. Perhaps the tissue most sensitive to pathological changes in the oral cavity is the periodontium. In cases of severe neutrophil dysfunction, there is severe periodontal breakdown, but also in cases of "mild" neutrophil dysfunction, where there is no other infection, such as in individuals with LJP, there is severe periodontal breakdown. The molecular basis of neutrophil dysfunction is beginning to be understood in individuals with LJP, LAD, CGD, and AIDS. It is our hope that further research in this area will help to delineate the pathogenesis of these and other oral diseases.

T-cell prolymphocytic leukemia with an unusual phenotype CD4+ CD8+

A patient with T-cell prolymphocytic leukemia (T-PLL) is described. The outcome was poor, with death 8 months after diagnosis, despite several therapeutic interventions. The cells carried both CD4 and CD8 epitopes, but other thymocytic markers were absent. The spleen showed infiltration of CD4+ CD8+ prolymphocytes in the red pulp and in T-cell-dependent areas of the white pulp. Immunologic function studies revealed proliferation after stimulation with mitogens and even several antigens. However, in the mixed lymphocyte culture the T-PLL cells did not proliferate. Cytotoxic T-cells could not be induced. In T-non-T recombination experiments neither helper nor suppressor cell function was found for pokeweed mitogen-dependent plasmablast generation of normal B-cells. Cytogenetically, many abnormalities were found. Among them, 14q+; absence of chromosomes 8, 11, and 22; and the presence of large marker chromosomes and fragments.

Granule enzymes of human and rabbit polymorphonuclear leukocytes: an investigation of enzyme solubility

Granules were isolated from both human and rabbit polymorphonuclear leukocytes (PMNs), and the quantity and solubility of certain granule enzymes compared. Lysozyme and alpha-mannosidase were found to be the most soluble enzymes in the granules of both species and could be released by lysis with 0.1% (v/v) Triton X-100. Alkaline phosphatase was also released by this lytic procedure, but its release required higher concentrations of Triton. The main difference between the species was found in the less-soluble enzymes that were retained as an insoluble complex after lysis by Triton X-100. Both myeloperoxidase and the neutral proteinase activity of rabbit PMNs were found to be highly insoluble, requiring 0.6 M sodium chloride for their extraction from this complex. The corresponding enzymes from human PMNs were more soluble, 0.15 M sodium chloride releasing the majority of the neutral proteinase activity. In addition, the insolubility of the rabbit neutral proteinase activity seemed to prevent its release from PMNs stimulated to degranulate in vitro by treatment with the calcium ionophore, A23187. Since rabbit PMNs were also shown to contain significantly less neutral proteinase activity than human PMNs, it would seem that the rabbit is a poor model for the study of PMN-mediated tissue injury in man.

Different molecular forms of a glycoprotein antigen found on azurophilic granule membranes of cultured human HL60 promyelocytes and on the plasma membrane of a myeloblastoid variant line

In previous immunohistological studies an antigen designated D46 was identified on the surface of an agranular, myeloblastoid cell line (HL60-D). It was not detected on the surface of either parental HL60 cells or variants with aberrant primary granules (HL60-A7). In these promyelocytes it was found to be intracytoplasmic, in a granular pattern. In the work presented here, this antigen and other granule-related glycoproteins were studied by radiolabeling, subcellular fractionation and gel electrophoresis. The major findings include the following: the anti-D46 antibody precipitated one major and one minor glycosylated component, each of which migrated with a different electrophoretic mobility, depending on whether it was derived from cells with or without granules. Incorporation of radioactive amino acids, but not monosaccharides, revealed an additional component of lower mobility. The D46 antigen(s) was recovered in the detergent-rich phase of a Triton X-114 extract of granules, suggesting that it is an integral membrane protein. As assessed by the relative activities of marker enzymes, the granules of both the HL60 and HL60-A7 cell lines exhibited a heterogeneous pattern of sedimentation in density gradients. The electrophoretic patterns of the major [2-3H]mannose-labeled glycoproteins of the granule-enriched fractions were similar, except for one diffuse band of 110-170 kD which was not detected in HL60-A7. These studies provide direct evidence for heterogeneity of enzymatic and membrane constituents of primary myeloid granules, and give the first indication that there may be glycoprotein changes associated with certain ultra-structural defects that occur in abnormal promyelocytes. They suggest also, in the example of the D46 antigen; that some glycoproteins may exist in different forms when localized to either the granules or the plasma membrane.

Ultrastructural localization of peroxidase activity in developing neutrophil granulocytes from human bone marrow

Developing neutrophil granulocytes of normal human bone marrow were investigated with the diaminobenzidine technique to determine the ultrastructural localization of peroxidase activity. Neutrophil granulocytes have three types of granule: nucleated, azurophil, and specific granules. These granules are produced consecutively during the eomyelocyte stage, the promyelocyte stage, and the myelocyte stage, respectively. The organelles involved in the production of granules, i.e., the nuclear envelope, rough endoplasmic reticulum, and Golgi apparatus, are peroxidase positive during the eomyelocyte and promyelocyte stages and peroxidase negative thereafter. This pattern differs for the granules themselves: nucleated granules are negative in the eomyelocyte and become positive in the promyelocyte. Azurophil granules become positive in the promyelocyte. Specific granules are negative. Our observations highly suggest that small Golgi-derived peroxidase-positive vesicles are involved in the maturation of both nucleated granules and azurophil granules.

Deficiency of myeloperoxidase and abnormal chromosome 1 occurs in variant (HL60) promyelocytes

Maturation of normal polymorphonuclear neutrophils is characterized by successive periods of granule synthesis, a process which frequently is abnormal in leukemia. Recently, the human leukemic cell line HL60, displaying a promyelocytic phenotype, has been used to study granulocyte maturation. We describe a variant line of HL60, called HL60-A7, resulting from growth in actinomycin D, which contains atypical large azurophilic granules deficient in myeloperoxidase. The products of in-vitro translation of A7 RNA contained less than 5% of the immunoreactive MPO found in the parent line. Electrophoresis of plasma membrane polypeptides radioiodinated by the lactoperoxidase technique revealed several differences. Karyotypic analysis identified a consistent chromosome 1q+ abnormality which was not found in any of the parental cells examined. This constellation of differences between HL60 and HL60-A7, i.e. MPO deficiency, abnormal granule morphology, cell surface changes, and further cytogenetic abnormalities, may point to a common site sensitive to altered regulation in some leukemic promyelocytes.

Atypical promyelocytic leukemia (M3) with immature primary granules and t(15;17)

An unusual case of acute myeloid leukemia with a standard t(15;17) is described. While light microscopy morphology was suggestive of acute myeloid leukemia M5a and light microscopy cytochemistry showed 80% of blasts to be strongly positive with Sudan Black B--more consistent with a diagnosis of M4--ultrastructural analysis demonstrated that the predominant cells were promyelocytes with immature primary granules hardly visible with the Romanovsky stains by light microscopy. Because typical cytologic and clinical features of M3 or M3 variant were lacking this atypical case would not have been recognized but for the presence of t(15;17) and the demonstration of promyelocytic features by electron microscopy.