Addition Of Granulocyte-macrophage Colony-stimulating Factor Research Articles

Hydroxychloroquine-Mediated Autophagy Inhibition Shifts Monocyte-Derived Dendritic Cells Toward Immunogenic Phenotype In Vitro

Dendritic cells (DCs) are recognized as the most potent antigen-presenting cells (APCs) and act as intermediaries between the innate and adaptive immune systems. The maturation and function of DCs are significantly influenced by autophagy. Hence, the current research evaluated the effect of hydroxychloroquine (HCQ), an autophagy inhibitor, on the maturation and activation of monocyte-derived DCs. Monocytes were cultured and induced to differentiate into monocyte-derived DCs by the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4) cytokines. After five days, the immature DCs were exposed to HCQ and Lipopolysaccharides (LPS), followed by a 24-hour incubation period. On the sixth day, the flow cytometry technique was employed to assess the impact of HCQ on the phenotypic characteristics of the DCs. Finally, the expression of both pro- and anti-inflammatory genes in the HCQ-treated and untreated DCs groups was examined using the real-time PCR method. DCs that were subjected to treatment with HCQ exhibited a notable augmentation in the expression of CD11c, CD86, and HLA-DR, which are markers associated with maturation and antigen presentation. Furthermore, the DCs treated with HCQ demonstrated a significant reduction in the expression of IL-10, TGF-β, and IDO genes, while displaying an increase in the expression of TNF-α and IL-12 when compared to the control group. These findings indicate that targeting autophagy can induce a shift in DCs towards an immunogenic state. However, further investigations are necessary to assess the impact of HCQ-treated DCs on T cell responses both in vitro and in vivo in tumor-bearing animal models.

Granulocyte-Macrophage Colony-Stimulating Factor Influence on Soluble and Membrane-Bound ICOS in Combination with Immune Checkpoint Blockade.

With the successful development of immune checkpoint blockade, there remains the continued need to improve efficacy and decrease toxicities. The addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) to ipilimumab has previously demonstrated both an improvement in efficacy and decrease in the incidence of high-grade adverse events. ICOS+CD4+ or ICOS+CD8+ peripheral blood T cells are significantly greater in the patients treated with ipilimumab plus GM-CSF than in the patients treated with ipilimumab alone. To better understand the effects of GM-CSF on inducible T-cell costimulator (ICOS) and clinical outcomes, the relative roles of identified soluble ICOS and membrane-bound ICOS were evaluated. The ICOS splice variant was secreted and found to have immunologic suppressive effects. Changes in soluble ICOS splice variant levels in treated patients correlated with clinical outcomes. GM-CSF enhanced membrane-bound ICOS in an IL12-dependent manner but did not increase soluble ICOS levels. Whereas soluble ICOS plays a role in immune suppression, GM-CSF efficacy involves increasing membrane-bound ICOS and induction of dendritic cell development. Thus, soluble ICOS splice variants may be used as a biomarker for GM-CSF and immune checkpoint blockade-based therapies.

Resveratrol Downregulates Granulocyte-Macrophage Colony-Stimulating Factor-Induced Oncostatin M Production through Blocking of PI3K/Akt/NF-κB Signal Cascade in Neutrophil-like Differentiated HL-60 Cells.

Oncostatin M (OSM) is essential in a wide range of inflammatory responses, and most OSM is produced by neutrophils in respiratory diseases. While resveratrol (RES) is regarded as an anti-inflammatory agent in a variety of conditions, the mechanism of OSM inhibition by RES in neutrophils remains to be elucidated. In this study, we investigated whether RES could inhibit OSM production in neutrophil-like differentiated (d)HL-60 cells. The effects of RES were measured by means of an enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and Western blotting. Increases in production and mRNA expression of OSM resulted from the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) in neutrophil-like dHL-60 cells; however, these increases were downregulated by RES treatment. Exposure to GM-CSF led to elevations of phosphorylation of phosphatidylinositol 3-kinase (PI3K), Akt, and nuclear factor (NF)-kB. Treatment with RES induced downregulation of the phosphorylated levels of PI3K, Akt, and NF-κB in neutrophil-like dHL-60 cells. These results suggest that RES could be applicable to prevent and/or treat inflammatory disorders through blockade of OSM.

Young microglia restore amyloid plaque clearance of aged microglia.

Alzheimer's disease (AD) is characterized by deposition of amyloid plaques, neurofibrillary tangles, and neuroinflammation. In order to study microglial contribution to amyloid plaque phagocytosis, we developed a novel exvivo model by co-culturing organotypic brain slices from up to 20-month-old, amyloid-bearing AD mouse model (APPPS1) and young, neonatal wild-type (WT) mice. Surprisingly, co-culturing resulted in proliferation, recruitment, and clustering of old microglial cells around amyloid plaques and clearance of the plaque halo. Depletion of either old or young microglial cells prevented amyloid plaque clearance, indicating a synergistic effect of both populations. Exposing old microglial cells to conditioned media of young microglia or addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) was sufficient to induce microglial proliferation and reduce amyloid plaque size. Our data suggest that microglial dysfunction in AD may be reversible and their phagocytic ability can be modulated to limit amyloid accumulation. This novel exvivo model provides a valuable system for identification, screening, and testing ofcompounds aimed to therapeutically reinforce microglial phagocytosis.

Review article: Hepatitis B and dialysis

The incidence of hepatitis B virus (HBV) infection in dialysis populations has declined over recent decades, largely because of improvements in infection control and widespread implementation of HBV vaccination. Regardless, outbreaks of infection continue to occur in dialysis units, and prevalence rates remain unacceptably high. For a variety of reasons, dialysis patients are at increased risk of acquiring HBV. They also demonstrate different disease manifestations compared with healthy individuals and are more likely to progress to chronic carriage. This paper will review the epidemiology, modes of transmission and diagnosis of HBV in this population. Prevention and treatment will be discussed, with a specific focus on strategies to improve vaccination response, new therapeutic options and selection of patients for therapy.

Addition of Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) to Trastuzumab Stabilizes Disease in Patients with Trastuzumab-Resistant, HER2+ Metastatic Breast Cancer.

Abstract Introduction: Trastuzumab with or without chemotherapy is the standard of care for patients with HER2+ metastatic breast cancer. The proposed mechanism of trastuzumab-induced regression of HER2+ tumors includes inhibition of tumor cell proliferation, potentiation of chemotherapy, and facilitation of immune function through antibody-dependent cell-mediated cytotoxicity. GM-CSF (Leukine) is a cytokine that mediates antibody-dependent cell-mediated cytotoxicity. We studied the feasibility and efficacy of adding GM-CSF to trastuzumab in patients with trastuzumab-resistant, HER2+ metastatic breast cancer.Patients and Methods: Patients with measurable, HER2+ metastatic breast cancer that progressed after treatment with trastuzumab with or without chemotherapy were continued on trastuzumab alone at 2 mg/kg intravenous weekly. GM-CSF (250 μg/m2 subcutaneous daily) was added until the absolute neutrophil count (ANC) was greater than 10,000/mm3, then given every other day while the ANC was maintained below 10,000/mm3. Disease was restaged every 8 weeks. Treatment with trastuzumab and GM-CSF was continued until disease progression or intolerable toxicity.Results: Of 18 eligible patients with progressive HER2+ metastatic breast cancer, 17 (median age 48 yr, range 27–75 yr) were evaluable. Nine had hormone receptor–positive disease. The median number of metastatic sites was 2 (range 1–3); the most common site was the liver (n=10). The median number of prior regimens (trastuzumab with or without chemotherapy) for metastatic disease was 2 (range 1–5). One patient developed rapidly progressive disease 2 weeks after the start of study therapy and died soon after. The other 16 patients continued treatment until disease progression. No disease response was observed, but 5 patients (29%) had stable disease with a median duration of 15.8 weeks (range 10–53.9 weeks). Thirteen patients had grade 1 toxic effects; 6 patients, grade 2; and 2 patients, grade 3 (fatigue and muscle aches). The most common toxic effect was rash at the injection site, followed by skin rash, fatigue, and muscle aches. No grade 4 or irreversible toxic effect was seen.Conclusion: The addition of GM-CSF to trastuzumab alone in patients with trastuzumab-resistant, HER2+ metastatic breast cancer stabilizes the disease for a median duration of 15.8 weeks without causing any significant toxic effects in 29% of heavily pretreated patients. Its administration is simple, safe, and feasible. This regimen, trastuzumab and GM-CSF, needs further evaluation in combination with chemotherapy or other biological agents. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5103.

The use of adjuvant granulocyte-macrophage colony-stimulating factor in HIV-related disseminated atypical mycobacterial infection

Mycobacterium avium complex (MAC) continues to be a challenging problem in some patients with advanced human immunodeficiency virus (HIV) infection despite the availability of potent chemotherapeutic agents. The use of adjunctive immunomodulatory therapy has shown promise in vitro, but there is currently limited supportive clinical evidence [Kemper CA, Bermudez LE, Derenski SC. Immunomodulatory treatment of Mycobacterium avium complex bacteraemia in patients with AIDS by use of recombinant granulocyte-macrophage colony-stimulating factor. J Infect Dis 1998;177:914-20; Kedzierska K, Johnson M, Mijch A, Cooke I, Rainbird M, Roberts S, et al. Granulocyte-macrophage colony-stimulating factor augments phagocytosis of Mycobacterium avium complex by human immunodeficiency virus type-1 infected monocytes/macrophages in vitro and in vivo. J Infect Dis 2000;181:390-94]. We report the resolution of MAC disease resistant to traditional therapy, in an HIV-infected individual, following the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF).

Immunomodulation of responses to active immunization with a polyvalent immunotherapeutic: cyclophosphamide, H2 blockade, IL-2/IFNα and GM-CSF

2564 Background: Strong humoral and cellular immune responses in patients with melanoma receiving a specific active immunotherapeutic (Canvaxin; CancerVax Corp, Carlsbad, CA) have been correlated with improved survival. We examined the impact of several immunomodulators on the strength of immune response. Methods: Analysis of sequential phase II clinical trials using Canvaxin alone (n=446) or in combination with cyclophosphamide (n=92), cimetidine (n= 357), indomethacin (n=54) or IL-2/INFα (n=71) was performed with regard to maximal immune response within 16 weeks of treatment. A randomized clinical trial (n= 97) of Canvaxin with or without the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) was also analyzed. Delayed-type hypersensitivity (DTH) to vaccine was measured in all trials. IgM and IgG responses to the TA90 tumor-associated antigen were measured prospectively in the GM-CSF trial. Results: DTH responses were greater in patients with stage IV melanoma with concurrent cyclophosphamide (mean induration 20.6 mm with cyclophosphamide vs. 14.2 without, p=0.011). This was not seen in patients with stage III disease or in any stage with cimetidine, indomethacin or IL-2/IFNα treatment. The randomized GM-CSF trial did not show a significant difference (by logistic regression) in maximal DTH response (15.9± 9.7 mm with GM-CSF vs. 16.7 ± 9.9 mm without). There was a significant increase in maximal anti-TA90 IgM titers in the GM-CSF arm (797 ± 622 vs. 541 ± 533; p=0.0123), but no difference in anti-TA90 IgG (680 ± 557 with GM-CSF vs. 612 ± 510 without GM-CSF.) Maximal absolute lymphocyte counts during treatment were also elevated in the GM-CSF arm. Adverse event profiles were not markedly different, but GM-CSF patients reported more grade 1–2 fatigue. Conclusions: These data suggest that the addition of cyclophosphamide to adjuvant active specific immunotherapy in stage IV melanoma impacts DTH responses, and GM-CSF increases IgM response. Since this represents an impact on both the cellular (DTH) and humoral (IgM) arms of immunity, further study of modulator combinations is warranted. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration CancerVax CancerVax

CX-659S, a Diaminouracil Derivative, Indirectly Inhibits the Function of Langerhans Cells by Blocking the MEK1/2-Erk1/2 Pathway in Keratinocytes

Keratinocytes are an important component of the skin immune system, and keratinocyte-derived cytokines control the function of Langerhans cells. We previously showed that CX-659S, a novel diaminouracil derivative, had an inhibitory effect on hapten-induced contact hypersensitivity reaction in mice. In this study, we investigated the mechanism by which CX-659S elicits its inhibitory effect. CX-659S inhibited the expressions of CD80 and CD86, but not that of CD54, on Langerhans cells in epidermal cell suspensions. Exogenous granulocyte-macrophage colony-stimulating factor restored the CX-659S-induced inhibition of CD80 and CD86 expressions of Langerhans cells. The production of interleukin-2 from allogeneic T cells was also inhibited when the cells were stimulated with CX-659S-treated epidermal cells, and this inhibition was suppressed by the addition of granulocyte-macrophage colony-stimulating factor during CX-659S treatment. As CX-659S significantly inhibited production of granulocyte-macrophage colony-stimulating factor from keratinocytes, CX-659S was thought to indirectly affect Langerhans cells by inhibiting the function of keratinocytes. These effects of CX-659S were preceded by blockade of the phosphorylation of extracellular-signal-regulated kinase 1/2 and their direct activators, mitogen-activated protein kinase/extracellular-signal-regulated kinase 1/2 (MEK1/2), but not p38 mitogen-activated protein kinase or inhibitory nuclear factor kappaBalpha, in keratinocytes. Furthermore, a specific MEK1/2 inhibitor, U0126, mimicked the effect of CX-659S. CX-659S, a keratinocyte-response modifier, would be an effective therapeutic compound to inhibit contact hypersensitivity reaction, its action mechanism being different from those of other immunosuppressive agents such as glucocorticosteroids or cyclosporine A.

Combined effects of Notch signaling and cytokines induce a multiple log increase in precursors with lymphoid and myeloid reconstituting ability

We investigated whether combined signaling induced by engineered Notch ligands and hematopoietic growth factors influences hematopoietic stem-cell differentiation. We show that incubation of murine marrow precursors with Delta1(ext-IgG), a Notch ligand consisting of the Delta1 extracellular domain fused to the Fc portion of human immunoglobulin G1 (IgG1), and growth factors stem cell factor (SCF), interleukin 6 (IL-6), IL-11, and Flt3-l inhibited myeloid differentiation and promoted a several-log increase in the number of precursors capable of short-term lymphoid and myeloid repopulation. Addition of IL7 promoted early T-cell development, whereas addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) led to terminal myeloid differentiation. These results support a role for combinatorial effects by Notch and cytokine-induced signaling pathways in regulating hematopoietic cell fate and suggest the usefulness of Notch ligand in increasing hematopoietic precursor numbers for clinical stem-cell transplantation.

Antidisialoganglioside/granulocyte macrophage–colony-stimulating factor fusion protein facilitates neutrophil antibody-dependent cellular cytotoxicity and depends on FcγRII (CD32) and Mac-1 (CD11b/CD18) for enhanced effector cell adhesion and azurophil granule exocytosis

Polymorphonuclear leukocytes (PMNs) mediate antibody-dependent cellular cytotoxicity (ADCC), which is increased by the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF). We sought to determine whether PMN ADCC also would be increased by the addition of an antibody/GM-CSF fusion protein and whether this would be associated with the up-regulation and activation of Mac-1 (CD11b/CD18) and with azurophil granule exocytosis. ADCC against LA-N-1 human neuroblastoma cells was evaluated with 4-hour calcein acetoxymethyl ester (calcein-AM) microcytotoxicity assay, electron microscopy, and multi-parameter flow cytometry. With the calcein-AM assay, LA-N-1 cell survival was 10%, 55%, and 75% when PMN ADCC was mediated by the antidisialoganglioside (anti-GD2) immunocytokine hu14.18/GM-CSF, by monoclonal antibody (mAb) hu14.18 mixed with GM-CSF, and by hu14.18 alone. Function-blocking mAbs demonstrated that FcgammaRII and FcgammaRIII were required for ADCC with hu14.18 alone or mixed with GM-CSF, but that only FcgammaRII was required for ADCC with hu14.18/GM-CSF. ADCC mediated by hu14.18 and hu14.18/GM-CSF was Mac-1 dependent. Electron microscopy demonstrated the greatest PMN adhesion, spreading, and lysis of targets with hu14.18/GM-CSF. Monoclonal antibodies blocking Mac-1 function allowed the tethering of PMN to targets with hu14.18/GM-CSF but prevented adhesion, spreading, and cytolysis. Flow cytometry showed that hu14.18 with or without GM-CSF and hu14.18/GM-CSF all mediated Mac-1-dependent PMN-target cell conjugate formation but that GM-CSF was required for the highest expression and activation of Mac-1, as evidenced by the mAb24-defined beta(2)-integrin activation epitope. Hu14.18/GM-CSF induced the highest sustained azurophil granule exocytosis, almost exclusively in PMNs with activated Mac-1. Thus, hu14.18/GM-CSF facilitates PMN ADCC against neuroblastoma cells associated with FcgammaRII and Mac-1-dependent enhanced adhesion and degranulation.

Bifurcation of osteoclasts and dendritic cells from common progenitors

AbstractOsteoclasts and dendritic cells are derived from monocyte/macrophage precursor cells; however, how their lineage commitment is regulated is unknown. This study investigated the differentiation pathways of osteoclasts and dendritic cells from common precursor cells at the single-cell level. Osteoclastogenesis induced by macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor–κB ligand (RANKL) or tumor necrosis factor-α (TNF-α) is completely inhibited by addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 at early stages of differentiation. GM-CSF–treated cells express both c-Fms and RANK and also low levels of CD11c and DEC205, which are detected on dendritic cells. Addition of GM-CSF also reduces expression of both c-Fos and Fra-1, which is an important event for inhibition of osteoclastogenesis. Overexpression of c-Fos by retroviral infection or induction in transgenic mice can rescue a failure in osteoclast differentiation even in the presence of GM-CSF. By contrast, differentiation into dendritic cells is inhibited by M-CSF, indicating that M-CSF and GM-CSF reciprocally regulate the differentiation of both lineages. Dendritic cell maturation is also inhibited when c-Fos is expressed at an early stage of differentiation. Taken together, these findings suggest that c-Fos is a key mediator of the lineage commitment between osteoclasts and dendritic cells. The lineage determination of osteoclast progenitors seen following GM-CSF treatment functions through the regulation of c-Fos expression.

Effects of cytokines and fluconazole on the activity of human monocytes against Candida albicans.

This study evaluates the effects of cytokines, used singly and in combination, on the microbicidal activity of human monocyte-derived macrophages (MDM) against intracellular Candida albicans in the presence and absence of fluconazole. In the absence of fluconazole, the addition of tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), gamma interferon (IFN-gamma), or IL-4 had no effect on the growth of C. albicans. In contrast, the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in decreased growth (P < 0.05), while the addition of IL-10 resulted in increased growth (P < 0.01). In the presence of fluconazole, only the addition of IFN-gamma resulted in an increase in the growth of C. albicans. In the presence or absence of fluconazole, all cytokine combinations except IFN-gamma plus GM-CSF caused significant decreases in growth (P < 0.01). IL-10 and IL-4 did not influence the activity of TNF-alpha or IL-1beta. In the absence or presence of C. albicans the addition of fluconazole, all of the cytokines studied, and combinations of fluconazole and selected cytokines caused increases in nitric oxide (NO) production (P < 0.01). Similar observations were made for superoxide (O(2)(-)) only in the presence of C. albicans. The greatest concentrations of NO and O(2)(-) were produced when C. albicans alone was present in the assays. Our results demonstrate that in the presence of low concentrations of fluconazole (0.1 times the MIC), selected cytokines and their combinations significantly increase the microbicidal activity of MDM against intracellular C. albicans.

Interferon alpha in combination with GM-CSF induces the differentiation of leukaemic antigen-presenting cells that have the capacity to stimulate a specific anti-leukaemic cytotoxic T-cell response from patients with chronic myeloid leukaemia

Although interferon alpha (IFN-alpha) is able to induce haematological remission in 60-80% of patients with chronic myeloid leukaemia (CML) in early chronic phase, major cytogenetic remissions are only achievable in 30-40%. Recent clinical data suggest that the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) to IFN-alpha therapy can significantly improve the cytogenetic response in some patients, although the mechanism remains unknown. We hypothesized that the combination of GM-CSF and IFN-alpha induces the differentiation of dendritic cells, which subsequently stimulates a specific anti-leukaemic response. Monocytes from CML patients were cultured in GM-CSF and interleukin (IL)-4 (GM/IL-4)or in GM-CSF and IFN-alpha (GM/IFN-alpha). After 7 d, the number of cells exhibiting typical antigen-presenting cell (APC) morphology was equal in both groups, and fluorescence in situ hybridization (FISH) analysis confirmed that the APCs generated with GM/IFN-alpha were of leukaemic origin. Phenotypically, both sets of APCs expressed typical surface markers; however, CD86, CD83, CD11c, HLA-ABC and HLA-DR expression was significantly higher in the GM/IFN-alpha APCs, whereas CD1a expression was significantly lower. In mixed lymphocyte reactions (MLR), GM/IFN-alpha APCs stimulated the proliferation of allogeneic T cells significantly better than GM/IL-4 APCs. However, both groups of APCs stimulated autologous T-cell proliferation equally. Finally, we assessed the ability of GM/IFN-alpha APCs to induce a leukaemia-specific cytotoxic T-cell response. Some samples generated cytotoxic T lymphocytes (CTLs) that specifically lysed bcr-abl-positive target cells. These data show that the combination of GM-CSF and IFN-alpha, when used in vitro, induces the differentiation of malignant APCs with potent T-cell stimulatory capacity. Although there is no in vivo evidence to support these findings, it is possible that, when administered to CML patients, GM-CSF in combination with IFN-alpha results in the generation of highly stimulatory leukaemic APCs.

The gp130-stimulating designer cytokine hyper-IL-6 promotes the expansion of human hematopoietic progenitor cells capable to differentiate into functional dendritic cells

Objective. Hyper-IL-6, a fusion protein of interleukin-6 and its specific receptor, together with stem cell factor leads to the proliferation of primitive hematopoietic progenitor cells. Based on these findings, the current study examined whether hyper-IL-6 promotes the growth of precursor cells that can be further differentiated into dendritic cells in the presence of additional cytokines. Methods. Dendritic cell cultures were generated from CD34 + hematopoietic progenitor cells derived either from bone marrow or from peripheral blood. CD34 + cells were cultured in the presence of cytokines for 2 weeks and then used for phenotyping and T-cell stimulation assays. Results. Hyper-IL-6 in the presence of stem cell factor induced a 60- to 80-fold expansion of CD34 + progenitor cells following 2 weeks of culture in serum-free medium. The addition of granulocyte-macrophage colony-stimulating factor to hyper-IL-6 and stem cell factor was essential for the differentiation of expanded progenitor cells into antigen presenting cells capable of inducing a primary T-cell response to soluble protein, which is a typical feature of dendritic cells. Phenotypic analyses confirmed the expansion of immature dendritic cells, which could be further differentiated into mature CD83 + dendritic cells under the influence of interleukin-4, interleukin-1β, tumor necrosis factor-α, and prostaglandin E 2. The capacity of expanded dendritic cells to stimulate protein-specific CD4 + T cells was used to stimulate a primary T-helper cell response to the recombinant protein of the hepatitis-B core antigen in healthy donors. Conclusion. The expansion and differentiation of functional dendritic cells from CD34 + progenitor cells under serum-free culture conditions allow for the possibility to develop more effective ways to immunize against viral infections and tumor diseases.

Epstein-Barr Virus Infects and Induces Apoptosis in Human Neutrophils

The role of neutrophils during Epstein-Barr virus (EBV) infection is not known. Disruption of the initial and nonspecific immune response may favor the spread of EBV infection. We have previously shown that EBV interacts with human neutrophils and modulates protein expression. In this study we have investigated the ability of EBV to infect neutrophils. Electron microscopy studies showed penetration of virus and its subsequent localization to the nucleus. The presence of viral genomes in isolated nuclei from neutrophils was also shown by polymerase chain reaction (PCR). Expression of viral transcripts like EBNA-2 (Epstein-Barr nuclear antigen-2) and ZEBRA (BamHI Z EBV replication activator) was not detected by reverse transcriptase (RT)-PCR, suggesting that EBV does not seem to establish a latent or a lytic infection in neutrophils. However, at 20 hours post-EBV infection, 77% of cells were apoptotic as compared to 22% in uninfected cell cultures, as evaluated by flow cytometry. This EBV-induced apoptosis was prevented by the addition of granulocyte-macrophage colony-stimulating factor to the cell cultures. Apoptotic cell death seems to implicate the Fas/Fas ligand (L) pathway, as reflected by an increase of Fas/Fas L expression on neutrophils treated with EBV and an increase of soluble Fas L, which may function in an autocrine/paracrine pathway to mediate cell death. Lastly, EBV genome was detected from neutrophils of infectious mononucleosis (IM) patients in contrast to neutrophils obtained from healthy EBV-seropositive donors. Our findings on the interactions of EBV with neutrophils will then provide new insights on the immunosuppressive effects associated with EBV infection.

Generation of dendritic cell-like antigen-presenting cells in long-term mixed leucocyte culture: phenotypic and functional studies.

The mechanisms contributing to the proliferation and differentiation of antigen-presenting cell (APC) precursors upon antigen stimulation or tissue injury are poorly understood. Herein, we report the induction of a population of dendritic cell-like cells (DLC) with potent antigen-presentation function from unfractionated spleen cells by means of repetitive allostimulation in long-term mixed leucocyte cultures (LT-MLC). Initially, only a few adherent DLC were observed. By 4-6 weeks, however, there were large numbers of DLC which survived persistently. Features of these DLC are closely related to dendritic cells (DC), including (1) dendritic, veiled or spiny-processed morphology; (2) expression of a wide array of leucocyte surface markers including DC-associated or restricted antigens: 33D1, NLDC-145, CD11c (N418), heat-stable antigen (HSA), CD44, B7-1 and B7-2; (3) ability to migrate to draining lymph nodes and white pulp area of spleen; (4) expression of high level of major histocompatability complex (MHC) class II molecules and (5) more potent mixed leucocyte reaction (MLR)-stimulating capacity than peritoneal macrophages and APC-enriched spleen cells. DLC-stimulated MLR was inhibited by monoclonal antibodies (mAbs) to B7-1, B7-2, intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), leucocyte-function associated antigen-1 (LFA-1) or very-late activation antigen-4 (VLA-4) by 30-55%. When maintained for more than 2 months, the DLC did not lose their MLR-stimulating activity, but many surface markers were down-regulated except for Mac-2 and VCAM-1, which remained stable or were up-regulated, respectively. In short-term culture, the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin (IL)-2 enhanced proliferation of DLC, while tumour necrosis factor-alpha (TNF-alpha) and IL-4 did not. IL-4 suppressed not only 'spontaneous', but also GM-CSF-enhanced proliferation, suggesting that cytokines play a differential role in DLC proliferation. These results confirm that professional APC can proliferate in response to repetitive antigen stimulation, and their proliferation is differentially regulated by cytokines. A comparison study of DLC with typical DC is being carried out in our laboratory.

19-Allylaminoherbimycin A, an analog of herbimycin A that is stable against treatment with thiol compounds or granulocyte-macrophage colony-stimulating factor in human leukemia cells

Herbimycin A, a benzoquinonoid ansamycin antibiotic, reduces intracellular phosphorylation by some protein tyrosine kinases and inhibits the proliferation of malignant cells which express high tyrosine kinase activity. Herbimycin A inhibited the proliferation of human monoblastic leukemia U937 cells, but this inhibition was abrogated by the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF). On the other hand, a derivative of herbimycin A, 19-allylaminoherbimycin A, inhibited the proliferation of such cells without interference by the addition of GM-CSF. Phosphorylation of MAP kinase and c- myc expression induced by GM-CSF in U937 cells were inhibited by both herbimycin A and 19-allylaminoherbimycin A. The time courses of growth inhibition showed that the growth-inhibitory activity of herbimycin A in U937 cells was initially potent, but gradually decreased in the presence of GM-CSF. Thiol compounds, glutathione (GSH) and 2-mercaptoethanol, abrogated the inhibition of the growth of U937 cells by herbimycin A, but not by 19-allylaminoherbimycin A, like GM-CSF. Intracellular GSH content in U937 cells was increased by treatment with GM-CSF, and decreased with herbimycin A, but returned to the control level with the addition of GM-CSF to herbimycin A. In thin-layer chromatography, after in vitro incubation with herbimycin A and GSH, nothing could be detected at the position of intact herbimycin A, while 19-allylaminoherbimycin A was stably detected. These findings suggest that changes in the intracellular concentration of GSH play a role in the abrogation of the inhibition of U937 cell growth by herbimycin A. In the presence of GSH, 19-allylaminoherbimycin A inhibited the proliferation of U937 cells and Philadelphia chromosome-positive K562 cells more effectively than herbimycin A. Since GSH plays a role in detoxicating several anticancer drugs, 19-allylaminoherbimycin A may have therapeutic advantages over herbimycin A against some types of leukemia.

Characterization of the protein tyrosine phosphatase CD45 on human epidermal Langerhans cells

Human Langerhans cells (LC) express CD45, but clear data about the isoform(s) and their function(s) are lacking. In the present study, double labeling experiments reveal that freshly isolated LC from normal skin are CD45RO+/RA-/RB-. However, after isolation and short-time culture where LC undergo an in vitro maturation resembling that to lymphoid dendritic cells, CD45RB emerges whereas CD45RO expression decreases. This evolution results from dynamic alternative RNA splicing. Addition of granulocyte-macrophage colony-stimulating factor or tumor necrosis factor-alpha to short-time cultures has no significant effect on CD45RB, but both cytokines accelerate the loss of CD45RO. LC isolated from lesional skin of atopic eczema highly express CD45RO and CD45RB. Cross-linking of CD45 on LC isolated from atopic individuals inhibits the calcium mobilization in response to activation via Fc epsilon receptor type I (Fc epsilon RI). Hence, the protein tyrosine phosphatase CD45 from human LC is subjected to a splicing phenomenon related to the differentiation and activation stage of these cells and regulates their Fc epsilon RI-mediated activation.

Granulocyte-Macrophage Colony-Stimulating Factor Induces Sequential Activation and Deactivation of Binding Via a Low-Affinity IgG Fc Receptor, hFcγRII, on Human Eosinophils

Eosinophils are important in antibody-mediated immune defense against parasites based on interaction with Ig receptors (FcR). Of the three classes of IgG FcR in humans, hFc gamma RI, II, and III, solely hFc gamma RII (CD32) is expressed on freshly isolated eosinophils. Despite an expression level similar to that found on monocytes and polymorphonuclear granulocytes, binding activity of hFc gamma RII on eosinophils is constitutively low. Freshly isolated eosinophils had a negligible ability to form rosettes with IgG-sensitized erythrocytes (EA-IgG). Addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) caused an approximately threefold increase in EA-IgG rosettes. This increase was maximal after 35 minutes, and declined upon further incubation at 37 degrees C. Analysis of hFc gamma RII expression levels showed no significant changes and neither was the expression of other hFc gamma R classes induced. Blocking studies with anti-Fc gamma receptor monoclonal antibody (MoAb) proved hFc gamma RII specificity of enhanced IgG complex binding. These phenomena were not restricted to GM-CSF action, because the addition of interleukin-3 or interleukin-5 similarly enhanced EA-IgG binding. The kinetics of activation of hFc gamma RII binding activity were paralleled by the binding of EA-C3bi to CR3 on eosinophils. In contrast to the stable expression of hFc gamma RII during activation with GM-CSF, CR3 expression increased slowly. Ligand binding via both types of opsonin receptors proved receptor specific. However, the kinetics of enhanced binding via hFc gamma RII and CR3 suggested the possibility of a common mechanism underlying the enhancement of ligand binding via hFc gamma RII and CR3. This hypothesis was supported by the fact that binding via hFc gamma RII proved sensitive to both high concentrations of F(ab')2 fragments of anti-CD11b MoAb MO1 and chelation of bivalent cations with EDTA. In conclusion, our studies indicate that cytokines can induce a transient enhancement of hFc gamma RII binding activity. Qualitative, and not quantitative, changes in this receptor appear to underly the modulation of binding activity, which may be linked to changes in CR3 activity.