scholarly journals Human neutrophils depend on extrinsic factors produced by monocytes for their survival response to TLR4 stimulation

2019 ◽  
Vol 25 (8) ◽  
pp. 473-486
Author(s):  
Shuvasree SenGupta ◽  
Madhavi J Rane ◽  
Silvia M Uriarte ◽  
Cassandra Woolley ◽  
Thomas C Mitchell
Keyword(s):  
Molecular Mechanisms ◽  
Lipid A ◽  
Ex Vivo ◽  
Cell Types ◽  
Human Neutrophils ◽  
Direct Stimulation ◽  
Extrinsic Factors ◽  
Gm Csf ◽  
Tnf Α ◽  
Neutrophil Survival

LPS delays neutrophil apoptosis by a process generally assumed to involve cell-intrinsic TLR4 signaling. However, neutrophil survival responses to LPS have been reported to be monocyte-dependent, which would indicate more complexity than is currently appreciated. We compared the survival responses of conventionally purified vs highly purified neutrophils to confirm or refute the need for secondary cell-types and to identify the cellular or molecular mechanisms involved. Direct stimulation of TLR4 failed to extend the survival of highly purified neutrophils, but survival activity was retained in less pure neutrophil preparations containing low numbers of eosinophils, monocytes, platelets and CD3+ lymphocytes. Sequential depletions identified monocytes as the only cell type required. Transfer of culture supernatants after lipid A-conditioning revealed that purified monocytes were sufficient for production of nearly all of the survival activity observed in mixed populations. The survival factors secreted upon TLR4 stimulation remain unidentified, but were not correlated with IL-1β, IL-6 or TNF-α nor could survival activity be inhibited by Ab blockade of IL-8 or of several other candidate factors other than endogenously produced GM-CSF, which was responsible for about one-tenth of the survival activity present in conditioned supernatants. These observations confirm that ex vivo neutrophil survival responses to TLR4 agonists are not cell intrinsic and involve potentially novel factors secreted by TLR4-stimulated monocytes.

Role of PI3-kinase–dependent Bad phosphorylation and altered transcription in cytokine-mediated neutrophil survival

Blood ◽  
2002 ◽  
Vol 100 (7) ◽  
pp. 2607-2616 ◽  
Author(s):  
Andrew S. Cowburn ◽  
Karen A. Cadwallader ◽  
Benjamin J. Reed ◽  
Neda Farahi ◽  
Edwin R. Chilvers
Keyword(s):  
Kinase Inhibitor ◽  
Apoptotic Cell ◽  
Pi3 Kinase ◽  
Human Neutrophils ◽  
Marginal Effect ◽  
Mrna Levels ◽  
Gm Csf ◽  
Tnf Α ◽  
Neutrophil Survival ◽  
Survival Effect

Phosphoinositide 3-kinase (PI3-kinase)–dependent phosphorylation of the proapoptotic Bcl-2 family member Bad has been proposed as an important regulator of apoptotic cell death. To understand the importance of this pathway in nontransformed hematopoietic cells, we have examined the effect of survival cytokines on PI3-kinase activity and Bad expression and phosphorylation status in human neutrophils. Granulocyte macrophage–colony-stimulating factor (GM-CSF) and tumor necrosis factor-α (TNF-α) both reduced the rate of apoptosis in neutrophils cultured in vitro for 20 hours. Coincubation with the PI3-kinase inhibitor LY294002, which in parallel experiments abolished GM-CSF–primed, fMLP-stimulated superoxide anion production and GM-CSF–stimulated PtdIns(3,4,5)P3accumulation, inhibited the GM-CSF and TNF-α survival effect. In contrast, the MAP kinase kinase (MEK1/2) inhibitor PD98059 and the protein kinase A inhibitor H-89 had only a marginal effect on GM-CSF–mediated neutrophil survival. GM-CSF substantially increased Bad phosphorylation at Ser112 and Ser136 and increased the cytosolic accumulation of Bad. GM-CSF also regulated Bad at a transcription level with a marked decrease in mRNA levels at 4 hours. TNF-α caused a biphasic effect on the rate of morphologic apoptosis, which corresponded to an early increase, and a late inhibition, of Bad mRNA levels. LY294002 inhibited GM-CSF– and TNF-α–mediated changes in Bad phosphorylation and mRNA levels. These data suggest that the survival effect of GM-CSF and TNF-α in neutrophils is caused by a PI3-kinase–dependent phosphorylation and cytosolic translocation of Bad, together with an inhibition of Bad mRNA levels. This has important implications for the regulation of neutrophil apoptosis in vivo.

scholarly journals Mcl-1 Expression in Human Neutrophils: Regulation by Cytokines and Correlation With Cell Survival

Blood ◽  
1998 ◽  
Vol 92 (7) ◽  
pp. 2495-2502 ◽  
Author(s):  
Dale A. Moulding ◽  
Julie A. Quayle ◽  
C. Anthony Hart ◽  
Steven W. Edwards
Keyword(s):  
Acute Inflammation ◽  
Molecular Mechanisms ◽  
Human Neutrophils ◽  
Potential Mechanism ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Regulated Gene Expression ◽  
Neutrophil Survival ◽  
Stimulating Factor

Abstract Human neutrophils possess a very short half-life because they constitutively undergo apoptosis. Cytokines, such as granulocyte-macrophage colony-stimulating factor (GM-CSF), and other agents can rescue neutrophils from apoptosis but the molecular mechanisms involved in this rescue are undefined. Here, we show by Western blotting that human neutrophils do not express Bcl-2 or Bcl-X but constitutively express Bax. However, cellular levels of these proteins are unaffected by agents which either accelerate or delay neutrophil apoptosis. In contrast, neutrophils express the antiapoptotic protein Mcl-1 and levels of this protein correlate with neutrophil survival. Thus, cellular levels of Mcl-1 decline as neutrophils undergo apoptosis and are enhanced by agents (eg, GM-CSF, interleukin-1β, sodium butyrate, and lipopolysaccharide) that promote neutrophil survival. Neutrophils only possess few, small mitochondria, and much of the Mcl-1 protein seems to be located in nuclear fractions. These observations provide the first evidence implicating a Bcl-2 family member in the regulation of neutrophil survival. Moreover, this work also provides a potential mechanism whereby cytokine-regulated gene expression regulates the functional lifespan of neutrophils and hence their ability to function for extended time periods during acute inflammation.

scholarly journals Mcl-1 Expression in Human Neutrophils: Regulation by Cytokines and Correlation With Cell Survival

Blood ◽  
1998 ◽  
Vol 92 (7) ◽  
pp. 2495-2502 ◽  
Author(s):  
Dale A. Moulding ◽  
Julie A. Quayle ◽  
C. Anthony Hart ◽  
Steven W. Edwards
Keyword(s):  
Acute Inflammation ◽  
Molecular Mechanisms ◽  
Human Neutrophils ◽  
Potential Mechanism ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Regulated Gene Expression ◽  
Neutrophil Survival ◽  
Stimulating Factor

Human neutrophils possess a very short half-life because they constitutively undergo apoptosis. Cytokines, such as granulocyte-macrophage colony-stimulating factor (GM-CSF), and other agents can rescue neutrophils from apoptosis but the molecular mechanisms involved in this rescue are undefined. Here, we show by Western blotting that human neutrophils do not express Bcl-2 or Bcl-X but constitutively express Bax. However, cellular levels of these proteins are unaffected by agents which either accelerate or delay neutrophil apoptosis. In contrast, neutrophils express the antiapoptotic protein Mcl-1 and levels of this protein correlate with neutrophil survival. Thus, cellular levels of Mcl-1 decline as neutrophils undergo apoptosis and are enhanced by agents (eg, GM-CSF, interleukin-1β, sodium butyrate, and lipopolysaccharide) that promote neutrophil survival. Neutrophils only possess few, small mitochondria, and much of the Mcl-1 protein seems to be located in nuclear fractions. These observations provide the first evidence implicating a Bcl-2 family member in the regulation of neutrophil survival. Moreover, this work also provides a potential mechanism whereby cytokine-regulated gene expression regulates the functional lifespan of neutrophils and hence their ability to function for extended time periods during acute inflammation.

scholarly journals TRAF6-IRF5 kinetics, TRIF, and biophysical factors drive synergistic innate responses to particle-mediated MPLA-CpG co-presentation

2021 ◽  
Vol 7 (3) ◽  
pp. eabd4235
Author(s):  
P. Pradhan ◽  
R. Toy ◽  
N. Jhita ◽  
A. Atalis ◽  
B. Pandey ◽  
...  
Keyword(s):  
Immune Responses ◽  
Molecular Mechanisms ◽  
Lipid A ◽  
Critical Role ◽  
Mouse Bone Marrow ◽  
Biophysical Properties ◽  
Gm Csf ◽  
Monophosphoryl Lipid A ◽  
Integrated Response ◽  
Particulate Carriers

Innate immune responses to pathogens are driven by co-presentation of multiple pathogen-associated molecular patterns (PAMPs). Combinations of PAMPs can trigger synergistic immune responses, but the underlying molecular mechanisms of synergy are poorly understood. Here, we used synthetic particulate carriers co-loaded with monophosphoryl lipid A (MPLA) and CpG as pathogen-like particles (PLPs) to dissect the signaling pathways responsible for dual adjuvant immune responses. PLP-based co-delivery of MPLA and CpG to GM-CSF–driven mouse bone marrow–derived antigen-presenting cells (BM-APCs) elicited synergistic interferon-β (IFN-β) and interleukin-12p70 (IL-12p70) responses, which were strongly influenced by the biophysical properties of PLPs. Mechanistically, we found that MyD88 and interferon regulatory factor 5 (IRF5) were necessary for IFN-β and IL-12p70 production, while TRIF signaling was required for the synergistic response. Both the kinetics and magnitude of downstream TRAF6 and IRF5 signaling drove the synergy. These results identify the key mechanisms of synergistic Toll-like receptor 4 (TLR4)–TLR9 co-signaling in mouse BM-APCs and underscore the critical role of signaling kinetics and biophysical properties on the integrated response to combination adjuvants.

scholarly journals Biologic properties in vitro of a recombinant human granulocyte- macrophage colony-stimulating factor

Blood ◽  
1986 ◽  
Vol 67 (1) ◽  
pp. 37-45 ◽  
Author(s):  
D Metcalf ◽  
CG Begley ◽  
GR Johnson ◽  
NA Nicola ◽  
MA Vadas ◽  
...  
Keyword(s):  
Colony Formation ◽  
Specific Activity ◽  
Human Neutrophils ◽  
Colony Stimulating Factor ◽  
Direct Stimulation ◽  
Gm Csf ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor ◽  
Marrow Cultures

Recombinant human granulocyte-macrophage colony-stimulating factor (rH GM-CSF) was purified to homogeneity from medium conditioned by COS cells transfected with a cloned human GM-CSF cDNA and shown to be an effective proliferative stimulus in human marrow cultures for GM and eosinophil colony formation. The specific activity of purified rH GM- CSF in human marrow cultures was calculated to be at least 4 X 10(7) U/mg protein. Clone transfer experiments showed that this proliferation was due to direct stimulation of responding clonogenic cells. Acting alone, rH GM-CSF did not stimulate erythroid colony formation, but in combination with erythropoietin, increased erythroid and multipotential colony formation in cultures of peripheral blood cells. rH GM-CSF had no proliferative effects on adult or fetal murine hematopoietic cells, did not induce differentiation in murine myelomonocytic WEHI-3B cells, and was unable to stimulate the survival or proliferation of murine hematopoietic cell lines dependent on murine multi-CSF (IL 3). rH GM- CSF stimulated antibody-dependent cytolysis of tumor cells by both mature human neutrophils and eosinophils and increased eosinophil autofluorescence and phagocytosis by neutrophils. From a comparison of these effects with those of semipurified preparations of human CSF alpha and -beta, it was concluded that rH GM-CSF exhibited all the biologic activities previously noted for CSF alpha.

scholarly journals Honokiol and Magnolol: Insights into Their Antidermatophytic Effects

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2522
Author(s):  
Adriana Trifan ◽  
Andra-Cristina Bostănaru ◽  
Simon Vlad Luca ◽  
Veronika Temml ◽  
Muhammad Akram ◽  
...  
Keyword(s):  
Negative Impact ◽  
Ex Vivo ◽  
Health Concern ◽  
Ergosterol Biosynthesis ◽  
Human Neutrophils ◽  
Traditional Use ◽  
Promising Alternative ◽  
Highly Active ◽  
Tnf Α ◽  
Significant Public Health

Dermatophyte infections represent a significant public health concern, with an alarming negative impact caused by unsuccessful therapeutic regimens. Natural products have been highlighted as a promising alternative, due to their long-standing traditional use and increasing scientific recognition. In this study, honokiol and magnolol, the main bioactives from Magnolia spp. bark, were investigated for their antidermatophytic activity. The antifungal screening was performed using dermatophyte standard strains and clinical isolates. The minimal inhibitory concentration (MIC) and the minimal fungicidal concentration (MFC) were determined in accordance with EUCAST-AFST guidelines, with minor modifications. The effects on ergosterol biosynthesis were assessed in Trichophyton rubrum cells by HPLC-DAD. Putative interactions with terbinafine against T. rubrum were evaluated by the checkerboard method. Their impact on cells’ viability and pro-inflammatory cytokines (IL-1β, IL-8 and TNF-α) was shown using an ex vivo human neutrophils model. Honokiol and magnolol were highly active against tested dermatophytes, with MIC and MFC values of 8 and 16 mg/L, respectively. The mechanism of action involved the inhibition of ergosterol biosynthesis, with accumulation of squalene in T. rubrum cells. Synergy was assessed for binary mixtures of magnolol with terbinafine (FICI = 0.50), while honokiol-terbinafine combinations displayed only additive effects (FICI = 0.56). In addition, magnolol displayed inhibitory effects towards IL-1β, IL-8 and TNF-α released from lipopolysaccharide (LPS)-stimulated human neutrophils, while honokiol only decreased IL-1β secretion, compared to the untreated control. Overall, honokiol and magnolol acted as fungicidal agents against dermatophytes, with impairment of ergosterol biosynthesis.

scholarly journals Activation of mitogen-activated protein kinase cascades during priming of human neutrophils by TNF-α and GM-CSF

1998 ◽  
Vol 64 (4) ◽  
pp. 537-545 ◽  
Author(s):  
Kenneth R. McLeish ◽  
Cindy Knall ◽  
Richard A. Ward ◽  
Par Gerwins ◽  
Patricia Y. Coxon ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Human Neutrophils ◽  
Gm Csf ◽  
Tnf Α ◽  
Mitogen Activated Protein

scholarly journals Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides

2017 ◽  
Vol 43 (6) ◽  
pp. 2170-2184 ◽  
Author(s):  
Jie Ma ◽  
Erich Gulbins ◽  
Michael J. Edwards ◽  
Charles C. Caldwell ◽  
Martin Fraunholz ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Confocal Microscopy ◽  
Inflammatory Cytokines ◽  
Cathepsin B ◽  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Clinical Problem ◽  
Acid Sphingomyelinase ◽  
Tnf Α ◽  
Factor Α

Background/Aims: Staphylococcus aureus (S. aureus) infections are a major clinical problem and range from mild skin and soft-tissue infections to severe and even lethal infections such as pneumonia, endocarditis, sepsis, osteomyelitis, and toxic shock syndrome. Toxins that are released from S. aureus mediate many of these effects. Here, we aimed to identify molecular mechanisms how α-toxin, a major S. aureus toxin, induces inflammation. Methods: Macrophages were isolated from the bone marrow of wildtype and acid sphingomyelinase-deficient mice, stimulated with S. aureus α-toxin and activation of the acid sphingomyelinase was quantified. The subcellular formation of ceramides was determined by confocal microscopy. Release of cathepsins from lysosomes, activation of inflammasome proteins and formation of Interleukin-1β (IL-1β) and Tumor Necrosis Factor-α (TNF-α) were analyzed by western blotting, confocal microscopy and ELISA. Results: We demonstrate that S. aureus α-toxin activates the acid sphingomyelinase in ex vivo macrophages and triggers a release of ceramides. Ceramides induced by S. aureus α-toxin localize to lysosomes and mediate a release of cathepsin B and D from lysosomes into the cytoplasm. Cytosolic cathepsin B forms a complex with Nlrc4. Treatment of macrophages with α-toxin induces the formation of IL-1β and TNF-α. These events are reduced or abrogated, respectively, in cells lacking the acid sphingomyelinase and upon treatment of macrophages with amitriptyline, a functional inhibitor of acid sphingomyelinase. Pharmacological inhibition of cathepsin B prevented activation of the inflammasome measured as release of IL-1β, while the formation of TNF-α was independent of cathepsin B. Conclusion: We demonstrate a novel mechanism how bacterial toxins activate the inflammasome and mediate the formation and release of cytokines: S. aureus α-toxin triggers an activation of the acid sphingomyelinase and a release of ceramides resulting in the release of lysosomal cathepsin B and formation of pro-inflammatory cytokines.

Interterleukin-6 (IL-6) Produced by Monocyte Activation Reduces Dendritic Cell (DC) Differentiation in Patients with Multiple Myeloma (MM) and Malignant Lymphoma (ML): Role of CNTO 328, an Anti-IL-6 Monoclonal Antibody (Mab) and Possible Clinical Applications.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2662-2662
Author(s):  
Jean-Francois Rossi ◽  
Anne-Marie Conge ◽  
Catherine Barjot ◽  
Mohamed H. Zaki ◽  
Marian T. Nakada ◽  
...  
Keyword(s):  
Large Scale ◽  
Ex Vivo ◽  
Immune Therapy ◽  
Human Albumin ◽  
Autologous Tumor ◽  
Vaccination Programs ◽  
Gm Csf ◽  
Free Process ◽  
Tnf Α ◽  
Dc Maturation

Abstract We developed a serum-free process in a closed system using culture cassettes and bags for large-scale and clinical-grade DC vaccination, accepted by the “Afssaps-French drug Agency” (Tarte K. et al. Leukemia2000; 14:2152 & patent). Intermediate mature DCs are generated from mononucleated cells obtained by mobilized leukapheresis, followed by Mo selection using adherence in specific cassettes (CLINIcell, Mabiol). Non-adherent cells are removed and Mo are cultured for 5 days (D) in X-VIVO15 medium (Cambrex) with 2% of human albumin, 100ng/ml of GM-CSF (Leukine, Berlex) and 25 ng/ml of IL-4 (CellGenix-Cellgen). At D5, immature DCs are harvested, pulsed with autologous tumor lysate (or peptides) for 4 h in X-VIVO15 medium + GM-CSF (100ng/ml) and maturation factors (TNF-α: 20ng/ml, CellGenix-CellGen, and PGE2: 100ng/ml; Prostine, Pharmacia). Maturation of DCs was allowed to proceed for 20 h with TNF-α and PGE2. Mo-conditioned media, or IL-6 as well as IL-1 are used for enhancing ex vivo DC maturation by different groups in spite of the fact that IL-6 has been described as a blocker of DC differentiation from CD34+ cells particularly in MM. We demonstrated that in our process, IL-6 is produced by activated Mo during their selection (mean= 378pg/mL, range 37–1219). The amount of the IL-6 released in the medium correlated with the % of CD14+ cells obtained at D5 (CD14<2.8%: mean IL-6=73.1 pg/mL; CD14>22.6%: mean IL-6=682.9 pg/mL), indicating that the intrinsic production of IL-6 is one major parameter of variability of the cellular product. By adding IL-6 from D1 to D5, the percentage of CD14+ cells at D5 was enhanced by a mean of 23-fold in samples from patients with MM (n=7) and 17-fold in ML (n=7). The modifications of other DCs markers including CD1a, CD 84 and CCR7 were modest. By using CNTO 328, an anti-IL-6 MAb (Centocor Inc) at 1–10μg/mL, we totally blocked the activity of added IL-6 and samples with high IL-6 intrinsic production, with a reduction of CD14+ cells at D5. In contrast, neither IL-6 nor CNTO 328 had any activity on terminal DC maturation after D5. IL-6 and CNTO328 are tested on DC functions. This means that in B-cell malignancies and other solid tumors with high levels of circulating IL-6: 1) anti-IL-6 treatment such as CNTO 328 may be associated with active immune therapy, including vaccinations; 2) mature and intermediate mature DCs are the only cells to be administered in vaccination programs because of a de-differentiation effect of immature DCs due to IL-6; 3) anti-IL-6 MAbs, particularly CNTO 328 could be added for ex vivo DC differentiation, instead of IL-6. mean % (range) of CD14+ cells at Day5 samples MM ML Control 2.9 (0.1–7.1) 12.2 (0–44.8) IL-6 (100ng/mL) 20 (6–35) 34.2 (0–71.4) IL-6+CNTO328 1μg/mL 2.8 (0.5–7.5) 15.7 (0–45.6) IL-6+CNTO328 10μg/mL 0.4 (0–0.8) 6.8 (0–20.3) CNTO328 1μg/mL 0.4 (0.1–0.7) 6.5 (0–19.5) CNTO328 10μg/mL 0.2 (0–0.4) 5.3 (0–15.3)

Distinct Human Cell Populations Produce Rapidly Detectable Levels of Neutrophils and Platelets in NOD/SCID-IL-2Receptor Gamma Chain Null Mice Transgenically Engineered to Produce Human Myeloid Growth Factors

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1892-1892
Author(s):  
Paul H. Miller ◽  
Alice M.S. Cheung ◽  
Suzan Imren ◽  
Philip A Beer ◽  
Shabnam Rostamirad ◽  
...  
Keyword(s):  
Progenitor Cell ◽  
Cell Types ◽  
Human Cells ◽  
Human Neutrophils ◽  
Short Term ◽  
Steel Factor ◽  
Gm Csf ◽  
Nsg Mice ◽  
Cd34 Cells

Abstract Abstract 1892 Cord blood (CB) is becoming an increasingly utilized source of cells for cancer patients who are eligible for therapies that require a transplant to rescue them from toxic side effects on their own hematopoietic cells but lack a suitable HLA-matched donor. This strategy is now routinely used in children, but delayed neutrophil and platelet recovery remain unsolved problems and these problems are exacerbated in adults. To address this issue, we first surveyed the variability in 8 individual CB harvests of parameters routinely used to predict the utility of CB units as transplants (i.e., CD34+ and in vitro myeloid clonogenic progenitor cell frequencies). In addition, we compared their 3-week outputs of CD33/15/66+ cells (neutrophils and monocytes) in the marrow and CD41a+ platelets in the blood of sublethally irradiated NSG mice after the IV transplantation of ∼104 CD34+ cells. These latter assessments were based on ongoing experiments in our lab demonstrating that, at this transplant dose, the outputs measured are linearly related to the number of CD34+ cells injected and detect transplantable progenitor cell types that are biologically distinct from cells with longer term repopulating activity. The results showed variation between CBs in all parameters, a marked lack of correlation between %CD34+ cells or % total CFCs in initial cells and %CD41a+ cells regenerated at 3 weeks/104 CD34+ cells transplanted (R=-0.28 and 0.35, respectively), and a weak correlation between the %CD33/15/66+ cells regenerated at 3 weeks/104 CD34+ cells transplanted and %CD34+ cells or % total CFCs in the initial CB cells (R values of 0.46–0.64). However, although engraftment of primitive human cells in NSG mice appears highly efficient, terminal differentiation of the myeloid lineages in these mice is poor. One possible explanation for this deficiency in mature cell output is that several of the murine growth factors responsible for regulating the production and release of these cells into the circulation in mice are not cross-reactive on human cells. We therefore hypothesized that engineering NSG mice to produce the human counterparts might significantly improve the detection of short term repopulating human cells whose maximum clone size might be limiting in NSG mice. Three potential relevant factors are IL-3, GM-CSF and Steel factor. We therefore backcrossed a line of transgenic NS mice we had created to express human IL-3, GM-CSF and Steel factor onto the NSG strain to produce homozygous NSG mice expressing all 3 of these human factors (NSG-3GS mice). We then compared these NSG-3GS mice with NSG mice in terms of their ability to stimulate the production within 3 weeks of human neutrophil-monocytes and platelets from intravenously transplanted CD34+ cells isolated from pooled CB harvests. The results showed that the levels of neutrophils and monocytes generated in the marrow of the NSG-3GS mice were elevated to levels of >50% of the marrow in 90% of the mice, even at the lowest number of CD34+ cells transplanted. Human neutrophils and monocytes were also elevated in the blood of the NSG-3GS mice where, despite the observed “saturation” of the marrow, there was a linear dose-response in the number of human neutrophils and monocytes present in the blood with increasing CD34+ cells infused. These findings are consistent with the reported activities of these molecules in vitro and in patients suggesting their physiological relevance in this murine xenograft model. We next utilized this assay to characterize the cells responsible for the neutrophil/monocyte and platelet repopulating activities detected in NSG-3GS mice. Preliminary assessment of the CD34+CD45RA- population on the basis of CD123 (IL-3 receptor alpha chain) expression indicates that the CD123+ fraction is enriched for short term (3-week) neutrophil/monocyte repopulating activity, while the CD123- fraction is enriched for short term (3-week) platelet repopulating activity. In summary, NSG-3GS mice significantly enhance the output of human cells with short term human myeloid repopulating ability thereby enabling neutrophil/monocyte outputs as well as platelet outputs to be assessed by analysis of peripheral blood samples. We have also used this tool to obtain evidence that these two outputs are derived from distinct cell types. Direct quantification of these may add to future predictions of graft quality. Disclosures: No relevant conflicts of interest to declare.

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