Granulocyte-macrophage colony-stimulating factor augments neutrophil killing of Torulopsis glabrata and stimulates neutrophil respiratory burst and degranulation

Neutrophils Require Activation to Express Functional Cell-Surface Complement Receptor Immunoglobulin

The phagocytosis-promoting complement receptor, Complement Receptor Immunoglobulin (CRIg), is exclusively expressed on macrophages. It has been demonstrated that expression in macrophages could be modulated by inflammatory mediators, including cytokines. This raised the possibility that a major phagocyte, the neutrophil, may also express CRIg following activation with inflammatory mediators. Here we show that resting peripheral blood neutrophil lysates subjected to protein analysis by Western blot revealed a 35 kDa CRIg isoform, consistent with the expression of CRIg mRNA by RT-PCR. By flow cytometry, CRIg was detected intracellularly and in very minor amounts on the cell surface. Interestingly, expression on the cell surface was significantly increased to functional levels after activation with inflammatory mediators/neutrophil activators; N-Formylmethionine-leucyl-phenylalanine, tumor necrosis factor (TNF), Granulocyte-Macrophage Colony stimulating Factor (GM-CSF), bacterial lipopolysaccharide, leukotriene B4 and phorbol myristate acetate. The increase in expression required p38 MAP kinase and protein kinase C activation, as well as intracellular calcium. Neutrophils which were defective in actin microfilament reorganization due to a mutation in ARPC1B or inhibition of its upstream regulator, Rac2 lose their ability to upregulate CRIg expression. Inhibition of another small GTPase, Rab27a, with pharmacological inhibitors prevented the increase in CRIg expression, suggesting a requirement for the actin cytoskeleton and exocytosis. Engagement of CRIg on TNF-primed neutrophils with an anti-CRIg monoclonal antibody increased the release of superoxide and promoted the activation of p38 but not ERK1/ERK2 or JNK MAP kinases. The TNF-induced increase in killing of Staphylococcus aureus was blocked by the anti-CRIg antibody. Adding to the anti-microbial role of CRIg, it was found that GM-CSF priming lead to the release of neutrophil extracellular traps. Interestingly in contrast to the above mediators the anti-inflammatory cytokine IL-10 caused a decrease in basal expression and GM-CSF induced increase in CRIg expression. The data demonstrate that neutrophils also express CRIg which is regulated by inflammatory mediators and cytokines. The findings show that the neutrophil antimicrobial function involving CRIg requires priming as a means of arming the cell strategically with microbial invasion of tissues and the bloodstream.

Multiple Phenotypic Changes Define Neutrophil Priming

Exposure to pro-inflammatory cytokines, chemokines, mitochondrial contents, and bacterial and viral products induces neutrophils to transition from a basal state into a primed one, which is currently defined as an enhanced response to activating stimuli. Although, typically associated with enhanced generation of reactive oxygen species (ROS) by the NADPH oxidase, primed neutrophils show enhanced responsiveness of exocytosis, NET formation, and chemotaxis. Phenotypic changes associated with priming also include activation of a subset of functions, including adhesion, transcription, metabolism, and rate of apoptosis. This review summarizes the breadth of phenotypic changes associated with priming and reviews current knowledge of the molecular mechanisms behind those changes. We conclude that the current definition of priming is too restrictive. Priming represents a combination of enhanced responsiveness and activated functions that regulate both adaptive and innate immune responses.

Distinct Effects of Integrins αXβ2 and αMβ2 on Leukocyte Subpopulations during Inflammation and Antimicrobial Responses

Integrins α_Mβ₂ and α_Xβ₂ are homologous adhesive receptors that are expressed on many of the same leukocyte populations and bind many of the same ligands. Although α_Mβ₂ was extensively characterized and implicated in leukocyte inflammatory and immune functions, the roles of α_Xβ₂ remain largely obscure. Here, we tested the ability of mice deficient in integrin α_Mβ₂ or α_Xβ₂ to deal with opportunistic infections and the capacity of cells derived from these animals to execute inflammatory functions. The absence of α_Mβ₂ affected the recruitment of polymorphonuclear neutrophils (PMN) to bacterial and fungal pathogens as well as to model inflammatory stimuli, and α_Mβ₂-deficient PMN displayed defective inflammatory functions. In contrast, deficiency of α_Xβ₂ abrogated intraperitoneal recruitment and adhesive functions of monocytes and macrophages (Mϕ) and the ability of these cells to kill/phagocytose Candida albicans or Escherichia coli cells both ex vivo and in vivo During systemic candidiasis, the absence of α_Xβ₂ resulted in the loss of antifungal activity by tissue Mϕ and inhibited the production of tumor necrosis factor alpha (TNF-α)/interleukin-6 (IL-6) in infected kidneys. Deficiency of α_Mβ₂ suppressed Mϕ egress from the peritoneal cavity, decreased the production of anti-inflammatory IL-10, and stimulated the secretion of IL-6. The absence of α_Xβ₂, but not of α_Mβ₂, increased survival against a septic challenge with lipopolysaccharide (LPS) by 2-fold. Together, these results suggest that α_Mβ₂ plays a primary role in PMN inflammatory functions and regulates the anti-inflammatory functions of Mϕ, whereas α_Xβ₂ is central in the regulation of inflammatory functions of recruited and tissue-resident Mϕ.

Neutrophil's weapons in atherosclerosis

Neutrophils are important components of immunity associated with inflammatory responses against a broad spectrum of pathogens. These cells could be rapidly activated by proinflammatory stimuli and migrate to the inflamed and infected sites where they release a variety of cytotoxic molecules with antimicrobial activity. Neutrophil antibacterial factors include extracellular proteases, redox enzymes, antimicrobial peptides, and small bioactive molecules. In resting neutrophils, these factors are stored in granules and released upon activation during degranulation. These factors could be also secreted in a neutrophil-derived microparticle-dependent fashion. Neutrophils exhibit a unique property to produce neutrophil extracellular traps (NETs) composed of decondensed chromatin and granular proteins to catch and kill bacteria. Neutrophil-released factors are efficient in inactivation and elimination of pathogens through oxidation-dependent or independent damage of bacterial cells, inactivation and neutralization of virulence factors and other mechanisms. However, in chronic atherosclerosis-associated inflammation, protective function of neutrophils could be impaired and misdirected against own cells. This could lead to deleterious effects and progressive vascular injury. In atherogenesis, a pathogenic role of neutrophils could be especially seen in early stages associated with endothelial dysfunction and induction of vascular inflammation and in late atherosclerosis associated with plaque rupture and atherothrombosis. Assuming a prominent impact of neutrophils in cardiovascular pathology, developing therapeutic strategies targeting neutrophil-specific antigens could have a promising clinical potential.

Hepatocyte growth factor stimulates neutrophil degranulation but not respiratory burst

Neutrophil function is regulated in part by cytokines with growth factor activities for different cell types. Hepatocyte growth factor (HGF) is a cytokine produced during injury to the liver and other organs. Neutrophils are numerous in such tissue injury sites and may be influenced by HGF. In the present study the effect of HGF on neutrophils was investigated. The data show that HGF at 1-10 ng/ml increased lysosomal enzyme release from both specific and azurophilic granules of cytochalasin-B treated neutrophils. The release of specific granule contents in response to N-formyl-methionyl-leucylphenylalanine was also increased by HGF. In contrast there were no significant effects of HGF on neutrophil respiratory burst, adherence or locomotion. It is concluded that HGF modulates neutrophil granule exocytosis.

Regulation of innate immune response to Candida albicans infections by αMβ2-Pra1p interaction

Candida albicans is a common opportunistic fungal pathogen and is the leading cause of invasive fungal diseases in immunocompromised individuals. The induction of cell-mediated immunity to C. albicans is one of the main tasks of cells of the innate immune system, and in vitro evidence suggests that integrin α(M)β₂ (CR3, Mac-1, and CD11b/CD18) is the principal leukocyte receptor involved in recognition of the fungus. Using α(M)β₂-KO mice and mutated strains of C. albicans in two models of murine candidiasis, we demonstrate that neutrophils derived from mice deficient in α(M)β₂ have a reduced ability to kill C. albicans and that the deficient mice themselves exhibit increased susceptibility to fungal infection. Disruption of the PRA1 gene of C. albicans, the primary ligand for α(M)β₂, protects the fungus against leukocyte killing in vitro and in vivo, impedes the innate immune response to the infection, and increases fungal virulence and organ invasion in vivo. Thus, recognition of pH-regulated antigen 1 protein (Pra1p) by α(M)β₂ plays a pivotal role in determining fungal virulence and host response and protection against C. albicans infection.

Candida glabrata tryptophan-based pigment production via the Ehrlich pathway

Pigments contribute to the pathogenicity of many fungi, mainly by protecting fungal cells from host defence activities. Here, we have dissected the biosynthetic pathway of a tryptophan-derived pigment of the human pathogen Candida glabrata, identified key genes involved in pigment production and have begun to elucidate the possible biological function of the pigment. Using transcriptional analyses and a transposon insertion library, we have identified genes associated with pigment production. Targeted deletion mutants revealed that the pigment is a by-product of the Ehrlich pathway of tryptophan degradation: a mutant lacking a tryptophan-upregulated aromatic aminotransferase (Aro8) displayed significantly reduced pigmentation and a recombinantly expressed version of this protein was sufficient for pigment production in vitro. Pigment production is tightly regulated as the synthesis is affected by the presence of alternative nitrogen sources, carbon sources, cyclic AMP and oxygen. Growth of C. glabrata on pigment inducing medium leads to an increased resistance to hydrogen peroxide, an effect which was not observed with a mutant defective in pigmentation. Furthermore, pigmented yeast cells had a higher survival rate when exposed to human neutrophils and caused increased damage in a monolayer model of human epithelia, indicating a possible role of pigmentation during interactions with host cells.

Resolution of Rhinocerebral Zygomycosis Associated with Adjuvant Administration of Granulocyte‐Macrophage Colony‐Stimulating Factor

We successfully treated 3 consecutive patients who had nonneutropenic rhinocerebral zygomycosis, by use of subcutaneous granulocyte-macrophage colony-stimulating factor therapy combined with traditional surgical and medical treatment. All patients are currently free of disease. Granulocyte-macrophage colony-stimulating factor should be considered as adjuvant therapy for rhinocerebral zygomycosis; however, optimum dose and length of therapy are unknown.

Colony-Stimulating Factors in Stem Cell Transplantation: Effect on Quality of Life

Health-related quality of life (QOL) is poorest during the immediate post-transplantation period, but the impact of medical interventions during this period has not been studied. Colony-stimulating factors (CSFs), which are used to minimize short-term negative outcomes, might be expected to improve QOL; however, little is published about their impact on QOL during this period. We conducted a MEDLINE search to identify studies reporting on outcomes of stem cell transplantation (SCT) affected by the CSFs, mainly sargramostim and filgrastim. End points studied were: mucositis, incidence and type of infection, duration of hospitalization, time to myeloid engraftment, and quantity and quality of harvested cells. To impute the impact of CSFs on QOL post-SCT, we also reviewed the association between QOL and CSF outcomes in other circumstances. Data suggest that both CSFs improve QOL in the early autologous or allogeneic post-bone marrow transplantation period. Poor QOL caused by infection and increased length of hospital stay is expected to be improved by sargramostim. Time to myeloid engraftment, when negatively affecting QOL, is expected to be improved with both CSFs; however, the time to myeloid engraftment is consistently shorter with filgrastim. Current prospective trials designed to study the effects of CSFs in the immediate post-SCT period should collect QOL data.

Mechanisms of the in vitro fungicidal effects of human neutrophils against Penicillium marneffei induced by granulocyte-macrophage colony-stimulating factor (GM-CSF)

We examined the in vitro fungicidal activity of human neutrophils against conidia and yeast cells of Penicillium marneffei. Neutrophils showed a small but significant anti-fungal effect against the yeast form of P. marneffei. Treatment of neutrophils with GM-CSF significantly augmented their anti-fungal activity. In contrast, the conidia form resisted killing even by stimulated neutrophils. Neutrophil fungicidal effect was not inhibited by superoxide dismutase (SOD), while the same treatment significantly suppressed the killing of Candida albicans by GM-CSF-stimulated neutrophils. For effective killing of P. marneffei yeast cells by GM-CSF-stimulated neutrophils, direct contact between the two was essential; interference in such interaction by separation using a 0. 45-microm-pored membrane prevented such an effect. Addition of colchicine attenuated GM-CSF-stimulated neutrophil fungicidal activity in a dose-dependent manner. This effect did not appear to be mediated by interference with neutrophil mobility toward yeast cells, because similar results were obtained when the cultures were set in round-bottomed wells which facilitate their direct contact. Finally, granular extracts derived from unstimulated neutrophils significantly suppressed the growth of microorganisms. Pretreatment of neutrophils with GM-CSF markedly enhanced this effect. The fungicidal activity of granular lysates was strongly, but not completely, reduced by heat treatment. Considered together, our results indicate that GM-CSF-stimulated neutrophils killed the yeast form of P. marneffei present in close proximity, probably in a superoxide anion-independent mechanism, but through exocytosis of granular enzymes which were largely heat-labile.

Cytokine-induced fungicidal activity of human polymorphonuclear leukocytes against Penicillium marneffei

We investigated the fungicidal activity of human polymorphonuclear leukocytes (PMN) against Penicillium marneffei. The yeast cells were cocultured in vitro with PMN for 24 h. Microscopic examination was also performed to examine the germination of yeast cells and their transformation to hyphal form during culture. Unstimulated PMN inhibited fungal growth when used at a higher effector/target (E/T) ratio but inhibited germination at a lower E/T ratio. We also examined the effects of various PMN-activating cytokines, including granulocyte-macrophage colony stimulating factor (GM-CSF), G-CSF, interleukin (IL)-8, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha on the activity of PMN. Among these, GM-CSF, G-CSF and IFN-gamma enhanced PMN activity from being fungistatic to fungicidal. However, the other cytokines had little or no effect on PMN activity. In contrast, all tested cytokines enhanced PMN inhibitory effects on germination and morphological changes of P. marneffei. These antifungal activities were most strongly induced by GM-CSF. The combined use of any of the above cytokines failed to synergistically enhance antifungal PMN activity. Our results demonstrated that cytokine-activated PMN exert a significant antifungal activity, by suppressing the growth and germination of P. marneffei. Our results suggest that PMN may contribute to host resistance to infection against this fungal pathogen.

Hematopoietic growth factors and acute leukemia

Over the past decade, with the advent of hematopoietic growth factors, major strides have been made and multiple studies have attempted to define the use of these cytokines in acute leukemia. It is perhaps disappointing that, after so many studies, so many questions remain. Nevertheless, the role of cytokines in induction therapy seems to be established, although questions remain around the issue of priming therapy. Intriguing data regarding the potential for enhancing antimicrobial function should hopefully be resolved over the next few years. What is perhaps most reassuring is that the issue of safety, which for a considerable period of time precluded the development of clinical trials in acute leukemia, has been firmly laid to rest. The use of growth factors to protect normal stem cells during treatment of leukemia and to induce leukemic cell differentiation has not yet been the subject of many clinical trials. Also, growth factors are likely targets for the interruption of autocrine leukemic blast or progenitor cell growth, but again, few clinical observations are published. With the ongoing cloning of new growth factors active both in normal hematopoiesis and in leukemogenesis, the role of growth factor use in the treatment of AML will likely be the basis for much future preclinical and clinical activity.

Comparison of neutrophil and monocyte function by microbicidal cell-kill assay in patients with cancer receiving granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, or no cytokine after cytotoxic chemotherapy: a phase II trial

Functional effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) and recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) were prospectively measured by harvesting blood samples from 51 oncology patients (21 who were receiving no cytokines, 14 receiving rhGM-CSF, and 16 who were receiving rhG-CSF) just before cytotoxic chemotherapy (baseline) immediately before the last cytokine dose (pre), 2 hours after the last cytokine dose (post), and 48 hours after the pre period (follow-up). Neutrophils and monocytes were separated and functional effects were measured by comparing cell-kill percentages, as determined by a microbial cell-kill assay against Staphylococcus aureus and Candida albicans. Optimal cell concentrations (2 x 10(6) monocytes/ml; 4 x 10(6) neutrophils/ml) and effector-to-cell ratios (1:50) were initially determined with blood samples harvested from 23 healthy volunteers. Results in oncology patients indicated that rhGM-CSF improved monocyte-killing activity against S. aureus at follow-up, compared with controls (p = 0.0094) and compared with monocytes from rhG-CSF-treated patients at the post period (p = 0.014). Cell-killing percentage of the rhGM-CSF-treated patients was also enhanced against C. albicans during the post period, compared with controls (p = 0.011) and rhG-CSF-treated patients (p = 0.067). Neutrophil activity was not altered by either cytokine. In conclusion, monocyte-induced microbial killing was enhanced in oncology patients receiving rhGM-CSF after cytotoxic chemotherapy, compared with patients receiving rhG-CSF or no cytokines. No differences in neutrophil activity were observed between patients receiving either cytokine.

Neutropenia and neoplasia: an overview of the pharmacoeconomics of sargramostim in cancer therapy

Sargramostim is a myeloid growth factor that is widely used as adjunctive support in patients with neutropenia. Sargramostim enhances neutrophil recovery and myeloid engraftment, reduces infectious complications, and shortens the duration of hospitalization in selected patients. The high cost of sargramostim and other myeloid growth factors and their ability to reduce infections and days of hospitalization have generated interest in their pharmacoeconomic impact. Cost minimization studies in patients receiving chemotherapy for acute myelogenous leukemia and in recipients of autologous bone marrow transplantation (BMT) show estimated cost savings with sargramostim of 1996 US$12,513 and 1994 US$14,500, respectively. These data are consistent with cost savings of 1989 US$16,000 using molgramostim in autologous BMT recipients. Although no pharmacoeconomic data have been published in patients with other conditions, clinical outcomes research demonstrates a clear benefit for sargramostim administration in recipients of peripheral blood progenitor cell and allogeneic BMT and in patients who experience graft delay or failure. Because of reductions in the duration of hospitalization and infectious complications, economic outcomes of these conditions would probably also support sargramostim use. More data regarding the use of sargramostim for chemotherapy-induced neutropenia are required to properly assess the pharmacoeconomic impact in these patients.

Tumor necrosis factor priming of peripheral blood neutrophils from rheumatoid arthritis patients

Recently it was shown that tumor necrosis factor-alpha (TNF) receptors on neutrophils may be down-regulated after stimulation with proinflammatory mediators. Since in rheumatoid arthritis neutrophils are likely to encounter these mediators in the circulation, we tested the hypothesis that rheumatoid arthritis neutrophil TNF receptors are down-regulated. Peripheral blood neutrophils from patients with rheumatoid arthritis and healthy subjects were compared with respect to their TNF binding activity and ability to be primed by TNF. There were no differences between rheumatoid arthritis and control neutrophils in receptor-mediated TNF binding, superoxide release in response to agonist, and TNF priming of this respiratory burst or in the ability to degrade cartilage in vitro and TNF priming for increased cartilage damage. It is evident that rheumatoid arthritis blood neutrophils retain the ability to bind TNF and can be primed by TNF for increased oxygen radical production and augmented cartilage damage. These findings further implicate the role of neutrophils in the pathogenesis of arthritis.

A radiologic syndrome after high dose chemotherapy and autologous bone marrow transplantation, with clinical and pathologic features of systemic candidiasis

BACKGROUND

The use of high dose chemotherapy in the treatment of solid tumors is associated with prolonged neutropenia and, consequently, in some patients, systemic candidiasis. The authors describe their experience with a clinicoradiologic syndrome developing after high dose chemotherapy was administered to patients with breast cancer.

METHODS

The authors evaluated the clinical and radiologic records of 12 patients in whom hepatic, splenic, or renal candidiasis developed.

RESULTS

Three patients had positive blood cultures for candida tropicalis. One of these patients and two others had fungal organisms identified with special stains of an organ aspirate. Most patients were asymptomatic, and most of them were treated successfully with antifungal agents, although untreated patients also recovered. There were no fatalities due to the candidiasis.

CONCLUSIONS

A radiographic syndrome resembling hepatic, splenic, or renal candidiasis is described, which occurred after high dose chemotherapy was administered and autologous bone marrow transplantation was performed on patients with breast cancer. This syndrome has a favorable prognosis. Conclusions as to the more indolent nature of this syndrome cannot be made; however, this topic warrants further investigation.

Role of IL-3 in the antiphospholipid syndrome

Antiphospholipid syndrome (APLS) is characterized by recurrent thromboembolic phenomena, thrombocytopenia and fetal loss. We describe various methods of induction of experimental APLS. These models were employed to study a variety of therapeutic agents including low dose aspirin, low molecular weight heparin, IVIG and thromboxane receptor antagonist. Because interleukin-3 (IL-3) is a multilineage cytokine affecting also megakaryocytes, is regarded as a 'good' cytokine in various stages of pregnancy and as low levels of IL-3 were recorded in APLS, it was logical to employ IL-3 as a therapy for APLS. Indeed, this treatment completely abrogated all the manifestations of experimental APLS. Furthermore, it was found that low dose aspirin most probably affect positively APLS via inducing an increased production of IL-3 by monocytes.

Treatment of disseminated Torulopsis glabrata infection with DO870 and amphotericin B

Torulopsis glabrata, an opportunist pathogen in immunosuppressed patients, is resistant to many antifungal agents, and there are no established treatment regimens for this organism. The mouse model was used to evaluate treatment with DO870, amphotericin B, fluconazole, and their combination. Mice were immunosuppressed with 5 mg of gold sodium thiomalate given intraperitoneally 1 day prior to intravenous infection with 10(8) T. glabrata cells. Treatment with a new antifungal triazole, DO870, at doses ranging from 1 to 50 mg/kg of body weight administered per os either daily or on alternate days; fluconazole at 100 mg/kg twice a day per os; or amphotericin B at 3 mg/kg/day intraperitoneally was begun 1 day after infection. Treatment for 5 days was followed by sacrifice 2 days later for determining CFU counts in spleen and kidney tissue. For a fluconazole-sensitive isolate (MIC of DO870, < 1.25 micrograms/ml), DO870 at 5 mg/kg/day significantly reduced counts in kidney and spleen tissue (P < 0.05), amphotericin B was modestly effective, and the combination of DO870 (25 mg/kg) and amphotericin B (3 mg/kg) was markedly more effective than either drug alone (P < 0.01). Three additional isolates were resistant in vitro to DO870 (MIC, 4 micrograms/ml). No reduction in CFU in kidney or spleen tissue was observed with DO870 when compared with counts in control tissue. DO870 is effective in vivo against at least some isolates of T. glabrata and when combined with amphotericin B can exert additive effects.

Effect of lysophosphatidic acid on motility, polarisation and metabolic burst of human neutrophils

The effect of lysophosphatidic acid (LPA) on human neutrophil activation was examined by a combination of automated tracking assays, cell shape measurements and assays of the metabolic burst by means of 7-dimethylamino-naphthalene-1,2-dicarbonic acid hydrazide (DNDH)-dependent chemiluminescence. LPA powerfully stimulated polarisation and motility. Polarisation became detectable at 2 microM LPA and virtually 100% of cells were polarised at 20 microM LPA. Cell motility increased with the degree of polarisation, and was diminished at high LPA concentration, but this decrease was reversed by albumin. LPA also inhibited the metabolic burst response to both n-formyl-methionyl-leucyl-phenylalanine (fMLP) and phorobol 12-myristate 13-acetate (PMA). Inhibition of the PMA-induced metabolic burst by LPA was not affected by pertussis toxin, showing that the effect was not mediated by the pertussis toxin-sensitive heterotrimeric G protein, and that inhibition of the PMA-stimulated metabolic burst by LPA could result from a direct action of LPA on the small cytosolic GTP-binding proteins. These results indicate that lysophosphatidic acid production by thrombin-activated platelets could play a significant role in the regulation of the inflammatory response.

Human recombinant GM-CSF selectively primes receptor mediated respiratory burst of neutrophils in vitro

The influence of human recombinant granulocyte-macrophage colony-stimulating factor (rH GM-CSF) on respiratory burst response of isolated human neutrophils was examined. Preincubation of cells with rH GM-CSF significantly increased the respiratory burst in response to formyl-methionyl-leucyl-phenylalanine (FMLP), measured by luminol-dependent chemiluminescence (CL) assay. This priming effect of rH GM-CSF was independent of extracellular Ca2+ and Mg2+. On the other hand, the pretreatment of cells with rH GM-CSF could not enhance the neutrophil CL responses to unopsonized, serum complement-opsonized or immunoglobulin G (IgG)-opsonized zymosan particles. rH GM-CSF directly induced a weak CL signal in neutrophils. This signal, however, was abolished when extracellular Ca2+ and Mg2+ were removed. Exposure to rH GM-CSF caused a divalent cation-dependent up-regulation of complement receptors (CR1 and CR3) on neutrophil cell surface, while the expression of IgG Fc-receptors (FcRII and FcRIII) was not markedly changed by rH GM-CSF. The results indicate that rH GM-CSF primes FMLP-induced CL but not zymosan particle-induced respiratory burst in human neutrophils. It is hypothesized that the reason for the different sensitivity of FMLP-receptors and receptors to zymosan particles to rH GM-CSF priming may lie in differences in the signal-transduction pathways of these receptor types.

Effect of granulocyte-macrophage colony-stimulating factor on leukocyte function in cirrhosis

BACKGROUND

Cirrhotic patients have been reported to have leukocyte impaired function as well as a high incidence of infectious diseases. Granulocyte-macrophage colony-stimulating factor (GM-CSF) increases the number and function of phagocytic cells, and clinical applications are under study. We tested in vitro effects of GM-CSF on phagocytosis, phagocytic index, and chemotaxis in polymorphonuclear leukocytes from 21 cirrhotic patients (12 with compensated cirrhosis and 9 with spontaneous bacterial peritonitis).

METHODS

Polymorphonuclear leukocyte functions were tested under basal conditions and after incubation with GM-CSF (10 ng/mL). Phagocytosis was tested against a clinical strain of Candida albicans, and chemotaxis was evaluated using a Boyden chamber. Results were compared with those obtained from 14 healthy donors.

RESULTS

Leukocytes from cirrhotics displayed lower basal functional activity than control cells in phagocytosis (P < 0.01) and chemotaxis (P < 0.01). After GM-CSF stimulation, the percentage of phagocytic polymorphonuclear leukocytes in noninfected patients increased from 60% +/- 2.5% to 69.9% +/- 2.42% (P < 0.01), phagocytic index from 0.79 +/- 0.07 to 1.02 +/- 0.07 (P < 0.001), and chemotaxis from 61.2 +/- 12.6 to 82.3 +/- 10.2 cells/high power field (P < 0.05). In patients with peritonitis, the phagocytic index increased from 0.87 +/- 0.08 to 1.08 +/- 0.05 (P < 0.01), phagocytosis from 57.8 +/- 3.57 to 64.7 +/- 2.34 and chemotaxis from 83.3 +/- 17.8 to 110.2 +/- 24.1.

CONCLUSIONS

Our results indicate that a defective leukocyte function is present both in compensated and infected cirrhotic patients. An in vitro improvement was observed after GM-CSF stimulation.

Serum-independent and serum-dependent cytoadherence in the interaction of Entamoeba histolytica with mammalian target cells

Entamoeba histolytica kills target cells only on direct contact, suggesting that trophozoite-mediated cytolysis is initiated by the contact between trophozoites and target cells. We have shown that adherence between E. histolytica and target cells (polymorphonuclear granulocytes, erythrocytes, Chinese hamster ovary cells, human colon carcinoma cells) was inhibited by specific carbohydrates, and adherence between E. histolytica and polymorphonuclear granulocytes (PMN) was enhanced by preincubation of the trophozoites with serum. Inhibition of adherence clearly paralleled inhibition of cytolysis and phagocytosis of target cells. Cytolysis of PMN, however, was not increased by preincubation of the trophozoites with serum. These results suggest that the effector functions of trophozoites are only dependent on carbohydrate-specific adherence mechanisms mediated by the amoebic Gal/GalNAc-binding lectin. E. histolytica trophozoites themselves can be killed by PMN, depending on the virulence of the trophozoites. PMN could not kill E. histolytica trophozoites more effectively when the adherence was enhanced by preincubation of the trophozoites with serum or when adherence was only mediated by serum-dependent mechanisms.

Upregulatory effects of cefpimizole natrium on human leukocytes

Cefpimizole natrium (CPIZ), an antibiotic belonging to the cephalosporins, was examined regarding its influence on neutrophil functions. Neutrophil superoxide (O2-) generation increased by intravenous CPIZ in patients with maxillofacial diseases. In vitro examination revealed that CPIZ directly stimulates neutrophils to generate O2- in a dose-dependent manner, though the induction ability is not as strong as phorbol myristate acetate (PMA). Protein kinase C (PKC) activity in the neutrophil plasma membrane increased after CPIZ treatment, while the activity in the cytosol fraction decreased. CPIZ cooperated with biological response modifiers (BRMs) such as sizofilan, lentinan, OK-432, rIL-2 and rIFN-gamma in neutrophil O2- generation. Non-specific cytotoxicity against K562 cells and candida cells was also enhanced by neutrophil pretreatment with both CPIZ and one of the BRMs except for sizofilan and rIL-2. From these results it can be concluded that CPIZ directly enhanced neutrophil O2- generation and that these CPIZ activations are further beneficial to protection against bacterial infections.

The role of GM-CSF in infection

GM-CSF is a hemopoietic growth factor with substantial effects on the proliferation of neutrophils, eosinophils and monocytes/macrophages. Its physiologic role in infection is still poorly understood. The gene for GM-CSF is constitutively transcribed in cells substantial for antiinfectious response. Various cells are activated and induced by TNF and IL-1 to synthesize GM-CSF. No systemic GM-CSF levels can be detected in patients with infection. It is likely that GM-CSF plays its physiological role in the immediate vicinity of the cells by which it is secreted. GM-CSF functionally activates neutrophils, monocytes/macrophages and eosinophils. It may augment T-cell proliferation and function. GM-CSF is effective in mice infected with Staphylococcus aureus or Salmonella typhimurium. Its effect in infectious disease in man should be explored.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF): receptor biology, signal transduction, and neutrophil activation

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) are two of the growing number of recognized cytokines involved in the regulation of hematopoiesis. The purification of these factors and the subsequent cloning of the cDNAs which encode these proteins have led to their widespread clinical use in the setting of therapy or disease-induced myelosuppression. Although originally purified on the basis of their colony-stimulating properties, GM-CSF and G-CSF may also play important roles in the regulation of effector cell function. The mechanisms underlying progenitor cell proliferation and effector cell stimulation remain poorly understood. However, the characterization of the GM-CSF and G-CSF receptors and recent work in signal transduction are helping to elucidate these mechanisms. This paper will review the biology of the GM-CSF and G-CSF receptors, the mechanisms of post-receptor signal transduction, and the resultant effects on neutrophil function. In addition, the current and potential clinical uses of these factors will be examined in light of their ability to activate and perhaps enhance the function of neutrophils.

Granulocyte-macrophage colony-stimulating factor augments neutrophil-mediated cartilage degradation and neutrophil adherence

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is produced in large quantities by synoviocytes in the inflamed arthritic joint and is known to be a neutrophil activator. Neutrophils predominate during acute flares of arthritis and are important mediators of cartilage destruction. In this investigation, we show that treatment of neutrophils with 10-1,000 units/ml of GM-CSF augments their ability to degrade cartilage proteoglycan in vitro. This was associated with increased neutrophil adherence to cartilage and increased release of oxygen-derived reactive species and granule enzymes in response to cartilage. Coating the cartilage with heat-aggregated human immunoglobulin G (AHG) enhanced both neutrophil adherence to the tissue and tissue degradation. GM-CSF, however, augmented these neutrophil effects independently of the presence of AHG. In contrast, neutrophil-mediated inhibition of proteoglycan synthesis was unaffected by GM-CSF.