Targeting Microglia-Synapse Interactions in Alzheimer's Disease.

In this review, we focus on the emerging roles of microglia in the brain, with particular attention to synaptic plasticity in health and disease. We present evidence that ramified microglia, classically believed to be "resting" (i.e., inactive), are instead strongly implicated in dynamic and plastic processes. Indeed, there is an intimate relationship between microglia and neurons at synapses which modulates activity-dependent functional and structural plasticity through the release of cytokines and growth factors. These roles are indispensable to brain development and cognitive function. Therefore, approaches aimed at maintaining the ramified state of microglia might be critical to ensure normal synaptic plasticity and cognition. On the other hand, inflammatory signals associated with Alzheimer's disease are able to modify the ramified morphology of microglia, thus leading to synapse loss and dysfunction, as well as cognitive impairment. In this context, we highlight microglial TREM2 and CSF1R as emerging targets for disease-modifying therapy in Alzheimer's disease (AD) and other neurodegenerative disorders.

Role of GM-CSF in a mouse model of experimental autoimmune prostatitis.

The etiology of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is still unknown. Granulocyte macrophage colony-stimulating factor (GM-CSF) has been shown to play an important role in the development of autoimmune and inflammatory diseases. Here, we investigated the expression and function of GM-CSF in patients with CP/CPPS and in a mouse model of experimental autoimmune prostatitis (EAP). GM-CSF mRNA levels were detected in expressed prostatic secretions samples from patients with CP/CPPS and in prostate tissue from a mouse model of EAP. The expression of GM-CSF receptor in mouse prostate and dorsal root ganglia were determined using PCR and immunohistochemistry. Behavioral testing and inflammation scoring were performed to evaluate the role of GM-CSF in disease development and symptom severity of EAP using GM-CSF knockout mice. mRNA levels of putative nociceptive and inflammatory markers were measured in the prostate after the induction of EAP. Elevated GM-CSF mRNA levels were observed in expressed prostatic secretions samples from patients with CP/CPPS compared with healthy volunteers. GM-CSF mRNA was also significantly increased in prostate tissue of the EAP mice model. The expression of GM-CSF receptors was confirmed in mouse prostate and dorsal root ganglia. GM-CSF knockout mice showed fewer Infiltrating leukocytes and pain symptoms after the induction of EAP. Deletion of GM-CSF significantly diminished EAP-induced increases of chemokine (C-C motif) ligand 2, chemokine (C-C motif) ligand 3, and nerve growth factor mRNA expression. The results indicated that GM-CSF plays a functional role in the pathogenesis of EAP. GM-CSF may function as a signaling mediator for both inflammation and pain transduction in CP/CPPS.

The Role of Zinc in GM-CSF-Induced Signaling in Human Polymorphonuclear Leukocytes.

SCOPE: Zinc is suggested to be necessary for functional signaling induced by certain growth factors. The granulocyte-macrophage colony-stimulating factor (GM-CSF) is a key factor for differentiation and activation of myeloid cells. This report analyses the impact of different zinc concentrations on GM-CSF-induced signaling in mature polymorphonuclear leukocytes (PMN). METHODS AND RESULTS: As measured by flow cytometry, zinc increases surface GM-CSF receptor (GM-CSFR) in PMN, whereas monocytes respond with decreased GM-CSFR surface expression. Since total cellular GM-CSFR expression remains unaffected, the observed zinc-induced GM-CSFR surface dynamics may be explained by receptor redistribution. In PMN, zinc enhanced phosphorylation of mitogen-activated protein kinases (MAPK) in a dose-dependent manner as found in western blot. Zinc-induced MAPK phosphorylation is additionally augmented by moderate GM-CSF stimulation. CONCLUSION: The present study demonstrates the opposing influence of zinc on GM-CSFR surface expression in monocytes and PMN. Zinc and GM-CSF, use in optimized concentrations, augment MAPK signaling, and increase expression of MAPK-induced myeloid cell leukemia-1 (Mcl-1) in PMN. Thus, this study concludes that zinc strengthens growth factor-induced signaling. Hence, the study provides a basis for further in vivo studies, focusing on the therapeutic value of zinc in patients with a disturbed GM-CSF signaling.

Enforced granulocyte/macrophage colony-stimulating factor signals do not support lymphopoiesis, but instruct lymphoid to myelomonocytic lineage conversion.

We evaluated the effects of ectopic granulocyte/macrophage colony-stimulating factor (GM-CSF) signals on hematopoietic commitment and differentiation. Lineage-restricted progenitors purified from mice with the ubiquitous transgenic human GM-CSF receptor (hGM-CSFR) were used for the analysis. In cultures with hGM-CSF alone, hGM-CSFR-expressing (hGM-CSFR+) granulocyte/monocyte progenitors (GMPs) and megakaryocyte/erythrocyte progenitors (MEPs) exclusively gave rise to granulocyte/monocyte (GM) and megakaryocyte/erythroid (MegE) colonies, respectively, providing formal proof that GM-CSF signals support the GM and MegE lineage differentiation without affecting the physiological myeloid fate. hGM-CSFR transgenic mice were crossed with mice deficient in interleukin (IL)-7, an essential cytokine for T and B cell development. Administration of hGM-CSF in these mice could not restore T or B lymphopoiesis, indicating that enforced GM-CSF signals cannot substitute for IL-7 to promote lymphopoiesis. Strikingly, >50% hGM-CSFR+ common lymphoid progenitors (CLPs) and >20% hGM-CSFR+ pro-T cells gave rise to granulocyte, monocyte, and/or myeloid dendritic cells, but not MegE lineage cells in the presence of hGM-CSF. Injection of hGM-CSF into mice transplanted with hGM-CSFR+ CLPs blocked their lymphoid differentiation, but induced development of GM cells in vivo. Thus, hGM-CSF transduces permissive signals for myeloerythroid differentiation, whereas it transmits potent instructive signals for the GM differentiation to CLPs and early T cell progenitors. These data suggest that a majority of CLPs and a fraction of pro-T cells possess plasticity for myelomonocytic differentiation that can be activated by ectopic GM-CSF signals, supporting the hypothesis that the down-regulation of GM-CSFR is a critical event in producing cells with a lymphoid-restricted lineage potential.

Understanding the dendritic cell lineage through a study of cytokine receptors.

Dendritic cells form a system of antigen presenting cells that are specialized to stimulate T lymphocytes, including quiescent T cells. The lineage of dendritic cells is not fully characterized, although prior studies have shown that growth and differentiation are controlled by cytokines, particularly granulocyte/macrophage colony-stimulating factor (GM-CSF). To further elucidate the nature and control of the dendritic cell lineage, we have studied the expression of specific cytokine receptors. Sufficient numbers of dendritic cells were purified from spleen and skin to do quantitative binding studies with radiolabeled M-CSF, GM-CSF, and interleukin 1 (IL-1). To verify the nonlymphoid nature of dendritic cells, we made an initial search for rearrangements in T cell receptor and immunoglobulin genes and none were found. M-CSF binding sites, a property of mononuclear phagocytes, also were absent. In contrast, GM-CSF receptors were abundant on mature dendritic cells, with approximately 3,000 binding sites/cell with a single Kd of 500-1,000 pM. Substantial numbers of high affinity (< 100 pM) IL-1 binding sites were identified as well; cultured epidermal dendritic cells (i.e., epidermal Langerhans cells) had 500/cell and spleen dendritic cells approximately 70/cell. Cross-linking approaches showed the 80-kD species that is expected of high-affinity type 1 IL-1 receptor. Anti-type 1 IL-1 receptor (R) mAbs also visualized these receptors by flow cytometry on freshly isolated epidermal dendritic cells. These results provide new evidence that dendritic cells represent a differentiation pathway distinct from lymphocytes and monocytes. Together with recent findings on the effects of IL-1 and GM-CSF on epidermal dendritic cells in situ (see Results and Discussion), the data lead to a proposal whereby IL-1 signals IL-1R to upregulate GM-CSF receptors and thereby, the observed responsiveness of dendritic cells to GM-CSF for growth, viability, and function.

Yolk-sac-derived macrophages progressively expand in the mouse kidney with age.

Renal macrophages represent a highly heterogeneous and specialized population of myeloid cells with mixed developmental origins from the yolk-sac and hematopoietic stem cells (HSC). They promote both injury and repair by regulating inflammation, angiogenesis, and tissue remodeling. Recent reports highlight differential roles for ontogenically distinct renal macrophage populations in disease. However, little is known about how these populations change over time in normal, uninjured kidneys. Prior reports demonstrated a high proportion of HSC-derived macrophages in the young adult kidney. Unexpectedly, using genetic fate-mapping and parabiosis studies, we found that yolk-sac-derived macrophages progressively expand in number with age and become a major contributor to the renal macrophage population in older mice. This chronological shift in macrophage composition involves local cellular proliferation and recruitment from circulating progenitors and may contribute to the distinct immune responses, limited reparative capacity, and increased disease susceptibility of kidneys in the elderly population.

Older people are more likely to develop kidney disease, which increases their risk of having other conditions such as a heart attack or stroke and, in some cases, can lead to their death. Older kidneys are less able to repair themselves after an injury, which may help explain why aging contributes to kidney disease. Another possibility is that older kidneys are more susceptible to excessive inflammation. Learning more about the processes that lead to kidney inflammation in older people might lead to better ways to prevent or treat their kidney disease. Immune cells called macrophages help protect the body from injury and disease. They do this by triggering inflammation, which aides healing. Too much inflammation can be harmful though, making macrophages a prime suspect in age-related kidney harm. Studying these immune cells in the kidney and how they change over the lifespan could help scientists to better understand age-related kidney disease. Now, Ide, Yahara et al. show that one type of macrophage is better at multiplying in older kidneys. In the experiments, mice were genetically engineered to make a fluorescent red protein in one kind of macrophage. This allowed Ide, Yahara et al. to track these immune cells as the mice aged. The experiments showed that this subgroup of cells is first produced when the mice are embryos. They stay in the mouse kidneys into adulthood, and are so prolific that, over time, they eventually become the most common macrophage in older kidneys. The fact that one type of embryonically derived macrophage takes over with age may explain the increased inflammation and reduced repair capacity seen in aging kidneys. More studies will help scientists to understand how these particular cells contribute to age-related changes in susceptibility to kidney disease.

Interleukin (IL)-3/granulocyte macrophage-colony stimulating factor/IL-5 receptor alpha and beta chains are preferentially expressed in acute myeloid leukaemias with mutated FMS-related tyrosine kinase 3 receptor.

The common beta chain subunit (beta(c)), also known as CDw131, shared by the interleukin-3 (IL-3), granulocytic macrophage colony-stimulating factor (GM-CSF) and IL-5 receptors, is required for high-affinity ligand binding and signal transduction. The present study explored the expression of CDw131 in 105 de novo cases of acute myeloid leukaemia (AML). The levels of CDw131 expression were used to identify two AML subgroups characterized by low (75/105) and high (30/105) expression of this receptor chain. It was observed that (i) the level of CDw131 expression strictly correlated with the level of CD116 (GM-CSFalpha receptor chain) and CD123 (IL-3Ralpha chain); (ii) AMLs with high CDw131 expression were characterized by low CD34 expression and usually high CD11b, CD14 expression; (iii) AMLs with high CDw131 expression frequently co-expressed receptors for angiogenic growth factors (vascular endothelial growth factor R2, Tie-2); (iv) AMLs with high CDw131 expression were more cycling than those with low CDw131 expression; (v) AMLs with high CDw131 frequently displayed Feline Murine Sarcoma (FMS-related) tyrosine kinase 3 (FLT3) internal tandem duplication and constitutively activated Signal Transducer and Activator of Transcription-5 (STAT5). In conclusion, the analysis of the level of CDw131 expression enabled the identification of a subset of AMLs characterized by a high cycling status, the expression of myelo-monocytic markers, mutated FLT3 and the co-expression of receptors for angiogenic growth factors. These findings are of value for the development of new therapeutic strategies for the treatment of these AMLs.

Single-cell, phosphoepitope-specific analysis demonstrates cell type- and pathway-specific dysregulation of Jak/STAT and MAPK signaling associated with in vivo human immunodeficiency virus type 1 infection.

Despite extensive evidence of cell signaling alterations induced by human immunodeficiency virus type 1 (HIV-1) in vitro, the relevance of these changes to the clinical and/or immunologic status of HIV-1-infected individuals is often unclear. As such, mapping the details of cell type-specific degradation of immune function as a consequence of changes to signaling network responses has not been readily accessible. We used a flow cytometric-based assay of signaling to determine Janus kinase/signal transducers and activators of transcription (Jak/STAT) signaling changes at the single-cell level within distinct cell subsets from the primary immune cells of HIV-1-infected donors. We identified a specific defect in granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven Stat5 phosphorylation in the monocytes of HIV-1+ donors. This inhibition was statistically significant in a cohort of treated and untreated individuals. Ex vivo Stat5 phosphorylation levels varied among HIV-1+ donors but did not correlate with CD4(+) T-cell counts or HIV-1 plasma viral load. Low Stat5 activation occurred in HIV-1-infected donors despite normal GM-CSF receptor levels. Investigation of mitogen-activated protein kinase (MAPK) pathways, also stimulated by GM-CSF, led to the observation that lipopolysaccharide-stimulated extracellular signal-regulated kinase phosphorylation is enhanced in monocytes. Thus, we have identified a specific, imbalanced monocyte signaling profile, with inhibition of STAT and enhancement of MAPK signaling, associated with HIV-1 infection. This understanding of altered monocyte signaling responses that contribute to defective antigen presentation during HIV-1 infection could lead to immunotherapeutic approaches that compensate for the deficiency.

Induction of apoptosis on K562 cell line and double strand breaks on colon cancer cell line expressing high affinity receptor for granulocyte macrophage-colony stimulating factor (GM-CSF).

BACKGROUND: Immunotoxins are comprised of both the cell targeting and the cell killing moieties. We previously established a new immunotoxin, i.e. Shiga toxin granulocyte macrophage-colony stimulating factor (StxA1-GM-CSF), comprises of catalytic domain of Stx, as a killing moiety and GM-CSF, as a cell targeting moiety. In this study, the ability of the immunotoxin to induce apoptosis and double strand breaks (DSB) on different cell lines was investigated. METHODS: The recombinant hybrid protein was expressed in bacterial expression system and purified with nickel-nitrilotriacetate acid resin. The K562 (erythroid leukemia) cell line and LS174 (colon carcinoma) were used in this study. The neutral comet assay was carried out for the detection of DSB and Hoechst staining was performed for apoptosis. RESULTS: StxA1-GM-CSF effectively induced apoptosis on K562 cell line and DNA Double Strand Break (DSB) were observed on colon cancer cell line treated with StxA1-GM-CSF. CONCLUSION: This novel action i.e. DNA damage might be a relevant mechanism of action for StxA1-GM-CSF that is designed to act as immunotoxin, although further investigation is required.

Unilineage monocytopoiesis in hematopoietic progenitor culture: switching cytokine treatment at all Mo developmental stages induces differentiation into dendritic cells.

We have developed a new culture system whereby human hematopoietic progenitors purified from adult peripheral blood extensively proliferate and gradually differentiate into >95% pure monocytic (Mo) cells. At all developmental stages treatment with interleukin (IL)-4+granulocyte-macrophage colony-stimulating factor or IL-4+c-Kit-ligand+FLT-3 ligand switched the Mo precursors into dendritic cells (DCs). The switching capacity decreased only at the end of the culture, when most Mo cells matured to macrophages. Moreover, the Mo precursors were highly susceptible to transduction with lentiviral vectors: once switched to DCs, they maintained the transgene expression, as well as the phenotype and function of the DC lineage. Our results provide new insight into the potential role of the Mo lineage as a reservoir of DCs in vivo. Furthermore, the methodology for transduction of Mo precursors provides a tool to generate genetically modified, normally functioning DCs potentially useful for immunotherapy.

Expression of the GM-CSF receptor in ovine spermatozoa: GM-CSF effect on sperm viability and motility of sperm subpopulations after the freezing-thawing process.

The granulocyte-macrophage colony stimulating factor (GM-CSF) is a pleiotropic cytokine capable of stimulating proliferation, maturation and function of haematopoietic cells. Receptors for this cytokine are composed of two subunits, alpha and beta, and are expressed in myeloid progenitors and mature mononuclear phagocytes, monocytes, eosinophils and neutrophils, as well as in other non-haematopoietic cells. We have previously demonstrated that bull spermatozoa express functional GM-CSF receptors that signal for increased glucose and vitamin-C uptake and enhance several parameters of sperm motility in the presence of glucose or fructose substrates. In this study, we have analyzed the expression of GM-CSF receptors in ovine spermatozoa and studied the effect of GM-CSF on sperm viability and motility after the freezing-thawing process. Immunolocalization and immunoblotting analyses demonstrated that ovine spermatozoa (Xisqueta race) expressed GM-CSF receptors. In addition, GM-CSF partially counteracted the impairing action of freezing/thawing on the percentage of total motility, as well as on the specific motility patterns of each of the separate, motile sperm subpopulations of ram ejaculates subjected to this protocol. These results suggest that GM-CSF can play a role in the resistance of ram spermatozoa to environmental thermal stress.

Chemotherapy-Induced IL34 Enhances Immunosuppression by Tumor-Associated Macrophages and Mediates Survival of Chemoresistant Lung Cancer Cells.

The ability of tumor cells to escape immune destruction and their acquired resistance to chemotherapy are major obstacles to effective cancer therapy. Although immune checkpoint therapies such as anti-PD-1 address these issues in part, clinical responses remain limited to a subpopulation of patients. In this report, we identified IL34 produced by cancer cells as a driver of chemoresistance. In particular, we found that IL34 modulated the functions of tumor-associated macrophages to enhance local immunosuppression and to promote the survival of chemoresistant cancer cells by activating AKT signaling. Targeting IL34 in chemoresistant tumors resulted in a remarkable inhibition of tumor growth when accompanied with chemotherapy. Our results define a pathogenic role for IL34 in mediating immunosuppression and chemoresistance and identify it as a tractable target for anticancer therapy. Cancer Res; 76(20); 6030-42. ©2016 AACR.

Cellular and molecular studies on the early stages of human hematopoietic differentiation in culture of pure progenitors.

Methodology has been developed that enables virtually complete purification and recovery of early hematopoietic progenitors from human adult blood, a minority of which is multipotent and endowed with self-renewal capacities, i.e., exhibits stem cell properties. This report briefly reviews: (i) the key steps involved in the progenitor purification and assay procedure; (ii) the characterization of "pure" progenitors at the level of membrane antigen pattern and response to HGFs; (iii) the development of a liquid suspension culture for the pure progenitors, which allows synchronized and selective erythroid or GM differentiation, and hence may be utilized for the analysis of molecular mechanisms underlying early and late stages of hematopoiesis; (iv) the study of the expression and modulation of HGFRs expressed on progenitors.

Flow cytometry measurement of GM-CSF receptors in acute leukemic blasts, and normal hemopoietic cells.

A quantitative analysis of expression levels of GM-CSF receptors was performed by flow cytometry in different disease categories, ie AML (n = 72), ALL (n = 18), and MDS (n = 12), as well as 12 healthy volunteers, using three different unconjugated GM-CSF/R monoclonal antibodies (McAbs) (HGM-CSFR (CD116), M5D12, 4B5F5), and appropriate standards. By using the reference HGM-CSFR McAb, in healthy subjects we found detectable levels of GM-CSF/R on blood monocytes (mean MESF (molecules of equivalent soluble fluorochrome)/cell: 36.1 x 10[3]), neutrophils (mean MESF/cell: 7.4 x 10[3]), bone marrow (BM) myelo-monocytic precursors (MESF range for the myeloid component, ie promyelocytes, myelocytes, metamyelocytes: 11.7-40.5 x 10[3], and for the monocytic lineage: 25.7-69.2 x 10[3]), and in two distinct subsets of BM CD34+ progenitor cells (GM-CSF/R dim: 2.5 x 10[3] MESF/cell, GM-CSF/R bright (10% of the total number of CD34 cells: 22.0 x 10[3] MESF/cell). In these subjects, there was no correlation between the expression levels of GM-CSF/R and CFU (CFU-GM, CFU-GEMM, BFU-E) colony production. Among the AML samples, M5D12 McAb was positive in 33%, 4B5F5 McAb in 90%, and HGM-CSF/R McAb in 78% of the cases examined (range of MESF/cell for the HGM-CSFR McAb: 0.9 x 10[3]-106.7 x 10[3]). The highest MESF values were seen in the M5 FAB subvariety (mean: 39.4 x 10[3]), where all the patients tested (n = 20) showed a strong positivity for the HGM-CSFR McAb. On the contrary, all ALL samples were GM-CSF/R negative except in two patients, who displayed a dim GM-CSF/R positivity (My+ALL: 1.3 x 10[3] MESF/cell; pro-B ALL: 1.0 x 10[3] MESF/cell). In most (>70%) M1 FAB subtypes, GM-CSF/R+ blasts co-expressed CD34low, HLA-DRhigh, CD33, CD38 antigens, and had little or no capacity to form CFU-GM colonies. GM-CSF/R+ blasts from the M5 FAB category were also positive for CD14, CD11c, CD33 and CD87. Furthermore, the number of GM-CSF/R expressed by leukemic cells from five out of 72 (7%) AML patients was above the highest values seen in normal samples (>69.2 x 10[3] MESF/cell), allowing the possibility of using this marker for the monitoring of the minimal residual disease (MRD) in a subset of AML. Cell culture studies aimed at evaluating GM-CSF receptor modulation following AML blast exposure to rhGM-CSF showed two distinct patterns of response; in the first group (6/10 cases) rhGM-CSF down-modulated GM-CSF receptors, whereas in the second group (4/10 cases), rhGM-CSF treatment was associated with either an increase or no change in the number of GM-CSF/R. In conclusion, cellular GM-CSF/R expression was variable and ranged from undetectable (ALL and a minority of AML) to very high intensities in M5 AML, and were also documented in some M0 AML, thus suggesting the concept that GM-CSF/R detection may be of help in lineage assignment of undifferentiated forms. Since the number of GM-CSF/R on AML blasts may be modulated after GM-CSF treatment, it can be postulated that the clinical use of GM-CSF in this disease may be optimized by a dynamic analysis of the number and the affinity status of GM-CSF-R in blasts and normal hemopoietic cells.

Effects of inducible MEK1 activation on the cytokine dependency of lymphoid cells.

The Raf/MEK/MAP kinase cascade plays a critical role in transducing growth signals from activated cell surface receptors. Using deltaMEK1:ER, a conditionally active form of MEK1, we demonstrate the ability of this dual specificity protein kinase to abrogate the cytokine dependency of the murine lymphoid hematopoietic cell line FL5.12. Cytokine-independent cells were obtained from FL5.12 cells at a frequency of 1 x 10(-7), indicating that a low frequency of cells expressing deltaMEK1:ER were factor-independent. In general, cells that were converted to a cytokine-independent phenotype displayed a higher level of MAP kinase activity in response to deltaMEK1:ER activation than those that remained cytokine-dependent. deltaMEK1:ER-responsive cells could be maintained long-term in the presence of beta-estradiol, as well as the estrogen-receptor antagonist 4-hydroxy-tamoxifen. Removal of hormone led to the rapid cessation of cell growth in a manner similar to that observed when cytokine is withdrawn from the parental cells. GM-CSF mRNA transcripts were detected in the MEK1-responsive cells indicating that activated deltaMEK1:ER may induce a pathway leading to autocrine proliferation. Cytokine-dependent deltaMEK1:ER cells were found to increase the expression of GM-CSF receptor alpha (GM-CSFRalpha) in response to beta-estradiol. In contrast, MEK1-responsive cells were found to express constitutively lower levels of GM-CSFRalpha and beta common (betac) chains indicating that constitutive GM-CSF expression resulted in a decrease in GM-CSFR expression. Treatment of parental cells with supernatant from MEK1-responsive FL5.12 cells was sufficient to promote [3H]-thymidine incorporation. GM-CSF was found to enhance the viability of FL5.12 cells. The cell lines described here will be useful for elaborating the ability of the MAP kinase pathway to regulate cell proliferation in hematopoietic cells.

Identification of mature and immature human thymic dendritic cells that differentially express HLA-DR and interleukin-3 receptor in vivo.

We have previously shown that thymic CD34+ cells have a very limited myeloid differentiation capacity and differentiate in vitro mostly into CD1a+-derived but not CD14+-derived dendritic cells (DC). Herein we characterized the human neonatal thymic DC extracted from the organ in relationship with the DC generated from CD34+ cells in situ. We show that in vivo thymic DC express E cadherin, CLA, CD4, CD38, CD40, CD44, and granulocyte-macrophage colony-stimulating factor-R (GM-CSF-R; CD116) but no CD1a. According to their morphology, functions, and surface staining they could be separated into two distinct subpopulations: mature HLA-DRhi, mostly interleukin-3-R (CD123)-negative cells, associated with thymocytes, some apoptotic, and expressed myeloid and activation markers but no lymphoid markers. In contrast, immature HLA-DR+ CD123hi CD36+ cells with monocytoid morphology lacked activation and myeloid antigens but expressed lymphoid antigens. The latter express pTalpha mRNA, which is also found in CD34+ thymocytes and in blood CD123hi DC further linking this subset to lymphoid DC. However, the DC generated from CD34+ thymic progenitors under standard conditions were pTalpha-negative. Thymic lymphoid DC showed similar phenotype and cytokine production profile as blood/tonsillar lymphoid DC but responded to GM-CSF, and at variance with them produced no or little type I interferon upon infection with viruses and did not induce a strict polarization of naive T cells into TH2 cells. Their function in the thymus remains therefore to be elucidated.

Variable cytotoxicity of diphtheria toxin 388-granulocyte-macrophage colony-stimulating factor fusion protein for acute myelogenous leukemia stem cells.

In this study, the utility of DT388-granulocyte-macrophage colony-stimulating factor (GM-CSF) for the ex vivo purging and direct administration to patients with acute myeloid leukemia (AML) is tested using clonogenic assays, long-term cultures (LTC), and NOD/SCID mice as assays for leukemic progenitors. We compare the ability of 24-hour exposure to 0.3 microg/mL (4 nM) DT388-GM-CSF to kill AML colony forming cells (CFC) and the more primitive AML progenitors detected after 6 weeks in stromal cocultures (AML LTC-initiating cells or AML LTC-IC) and after 8 weeks in NOD/SCID mice.AML samples (n = 10), expressing a mean of 35 to 1466 GM-CSF receptors/blast, showed mean (range) percent kills of AML CFC and LTC-IC of 61 (17-98) and 46 (0-94) respectively with a direct correlation (r = 0.69) between the % kills detected in the in vitro assays. Among 5 evaluable samples the percent reduction in AML cell engraftment in NOD/SCID marrow following ex vivo DT388-GM-CSF treatment varied from 38% to 100%. 40% to 56% of normal bone marrow CFC and 31% to 48% of normal LTC-IC survived the same ex vivo treatment (n = 3). In subsequent experiments, NOD/SCID mice received AML blast cell injections intravenously followed in 24 hours by 1.5 microg DT388-GM-CSF daily intraperitoneally for 5 days. A reduction of marrow blast cells was seen with 7 of 9 samples tested 4 to 12 weeks post one course of toxin. Repeating the 5-day course of toxin 2 or 3 times at 4-week intervals did not improve the response, while delaying administration until 4 to 8 weeks post AML cell injection reduced the toxin's effectiveness (n = 5).This fusion toxin may prove useful for in vitro purging of stem cell harvests from selected AML patients and for direct administration to such patients.

Perilesional injection of r-GM-CSF in patients with cutaneous melanoma metastases.

Based on evidence that granulocyte-macrophage colony stimulating factor (GM-CSF) induces a potent systemic antitumor immunity, we tested recombinant GM-CSF in advanced melanoma. Seven patients with histologically confirmed cutaneous melanoma metastases were treated with perilesional intracutaneous injections of recombinant GM-CSF and observed for a follow-up time of 5 y. All but two patients had a decrease in the total number of metastases. At the end of the 5 y follow-up three of the seven patients are still alive with only one patient receiving other than surgical therapy, and one patient died tumor free at the age of 93. The remaining three patients died from progressive melanoma. Perilesional intradermal GM-CSF therapy resulted in a mean survival time of 33 mo. The treatment was well tolerated and no side-effects other than local erythema at the injection sites and mild drowsiness were seen. Immunohistochemical analysis with staining for CD14 and GM-CSF receptor demonstrated an increased infiltration of monocytes into both injected and noninjected cutaneous melanoma metastases compared with lesions excised prior to the initiation of therapy. The same was true for CD4- and CD8-positive lymphocytes. This phenomenon, together with GM-CSF-induced leukocyte counts of more than 20,000 during therapy, support the possible impact of a systemic over a locally induced reaction by GM-CSF. To our knowledge this is the first report that intracutaneously injected GM-CSF results in long-lasting reduction of melanoma metastases.

Regulation of transforming growth factor-beta1 expression by granulocyte macrophage-colony-stimulating factor in leiomyoma and myometrial smooth muscle cells.

Human myometrium and leiomyomas express granulocyte macrophage-colony-stimulating factor (GM-CSF), transforming growth factor-beta (TGFbeta), and their receptors. Overexpression of TGFbeta and, to a limited extent, GM-CSF has been associated with tissue fibrosis throughout the body, including leiomyomas. The objective of the present study was to determine the action of GM-CSF on leiomyoma and myometrial smooth muscle cells (LSMC and MSMC) and examine whether the action of GM-CSF is mediated through the induction of TGFbeta1 expression. Using competitive quantitative RT-PCR and enzyme-linked immunosorbent assay, we found that LSMC express significantly higher GM-CSF messenger ribonucleic acid (mRNA; 0.6 +/- 0.1 x 10(3) copies of mRNA/microg total RNA) and protein (0.75 +/- 0.2 ng/mL) than MSMC (0.5 +/- 0.1 x 10(2) copies of mRNA and 0.45 +/- 0.07 ng/mL protein; P < 0.05). In addition, LSMC expressed significantly higher TGFbeta1 mRNA (1.6 +/- 0.3 x 10(4) copies of mRNA/microg total RNA) than MSMC (2.4 +/- 0.4 x 10(3) copies) and synthesized and secreted more TGFbeta1 protein (1.7 +/- 0.2 vs. 0.5 +/- 0.02 ng/mL); whereas MSMC contained more cell-associated TGFbeta1 (56.2 +/- 1.2 ng/mL) than LSMC (35.2 +/- 1.2 ng/mL; P < 0.05). We found that GM-CSF (0.01-100 ng/mL) has limited mitogenic activity for LSMC but not for MSMC determined by the rate of [3H]thymidine incorporation and cell proliferation assay. However, GM-CSF at 1 ng/mL increased its own production, the expression of TGFbeta1 mRNA, the cell-associated TGFbeta1 protein content in both cell types, and TGFbeta1 released into the culture-conditioned medium of LSMC (P < 0.05). TGFbeta1 also increased its own mRNA and protein expression, but had no effect on cell-associated TGFbeta1 in both cell types (P < 0.05). Cotreatment of LSMC and MSMC with GM-CSF and TGFbeta1 induced changes similar to those produced by GM-CSF in both cells. In conclusion, our data suggest that GM-CSF is not a mitogen for MSMC and LSMC, but it regulates its own expression and the expression of TGFbeta1 by these cells, a regulatory interaction that may account for the GM-CSF-induced tissue fibrosis that occurs in leiomyomas.

An immunoenzyme technique for the identification of granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors using digoxigenated-GM-CSF.

A method for detecting granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors has been devised using human macrophages and a GM-CSF/IL-3-dependent human megakaryoblastic leukemia cell line (M-07e). Recognition of the factor-binding site was accomplished by linking recombinant human (rh) unglycosylated GM-CSF previously labeled with digoxigenated compounds. Digoxigenates were able to link amino and sulphydryl groups of the soluble factor and an immunoperoxidase technique using monoclonal anti-digoxigenin antibody was employed to demonstrate the interaction. To support morphological data cross-linking analysis was performed with M-07e cells using digoxigenated-rh-GM-CSF. Macrophages and M-07e cells incubated with digoxigenated-rh-GM-CSF showed intense positivity by the immunoperoxidase technique. In cross-linking, M07e cells showed a 96 kDa band corresponding to receptor plus bound factor. This technique permits a high degree of specificity in the detection of GM-CSF receptors with good morphological preservation of cellular detail.