Granulocyte-macrophage Colony-stimulating Factor Receptor Alpha Research Articles

A Phase I/II Clinical Trial of Piggybac-Modified GMR CAR-T Cell Therapy for CD116 Positive Relapsed/Refractory Myeloid Malignancies

Background: The prognosis of relapsed/refractory (R/R) myeloid malignancies remains poor, and the development of novel treatment strategies is crucial. Although chimeric antigen receptor (CAR)-modified T cell therapy for B cell malignancies has shown excellent clinical efficacy, the use of CAR-T cells for myeloid malignancies has been more challenging, partly due to the heterogeneous expression of candidate target antigens in leukemia cells and shared expression of those antigens in normal myeloid cells or progenitor cells. We previously developed the piggyBac-modified chimeric antigen receptor (CAR)-T cells targeting CD116, also known as GM-CSF receptor alpha chain (GMR) (Nakazawa Y, et al. J Hematol Oncol. 2016 and Hasegawa A, et al. Clin Transl Immunology. 2021). GMR CAR-T cells showed substantial antitumor effects against both acute myeloid leukemia and juvenile myelomonocytic leukemia. Moreover, modulation of the spacer and antigen recognition site of the CAR vector further enhanced the anti-tumor effects of GMR CAR-T cells. GMR CAR-T cells showed an acceptable safety profile with limited cytotoxicity on normal hematopoietic cells except monocytes. Based on these results, we have initiated a first-in-human clinical trial of GMR CAR-T cell therapy in March 2021 in Japan.Study Design and Methods: The study is a phase I/II, single-center, dose-escalation study with a traditional 3+3 dose-escalation design (Table 1). Maximum of 18 patients will be recruited. Primary objectives of this study are to determine the safety and severe adverse events of piggyBac-modified GMR CAR-T cells for CD116 + relapsed/refractory myeloid malignancies by assessing the dose-limiting toxicity within 28 days from the single infusion of GMR CAR-T cells.The patients with CD116 + myeloid malignancies aged more than 1 year with myeloid malignancies who experienced an induction failure or a relapse after hematopoietic stem cell transplantation (HSCT) will be recruited. CD116 is defined as positive when a CD116 relative mean fluorescence (RFI) in leukemia cells ≥ 2. RFI was calculated by dividing the MFI of samples with that of the isotype control. Major exclusion criteria are as follows, acute promyelocytic leukemia, acute graft-versus-host disease (GVHD) (Grade ≥ 2), extensive chronic GVHD, and concurrent treatment with corticosteroid (≥ 6 mg/m2). Statistical analysis will be performed when the data will be fixed.Peripheral blood mononuclear cells will be harvested from the patient by leukapheresis and then will be transduced with GMR CAR vector by piggyBac transposon system. All manufacturing process of GMR CAR-T cells is performed in Cell Processing Center in Shinshu University Hospital under good manufacturing practice conditions. The patient will be treated with lymphodepleting chemotherapy consisting of fludarabine and cyclophosphamide, followed by CAR-T cell infusion. The dose of CAR-T cells will be 3 x 10 5 and 1 x 10 6 in cohorts 1 & 2 and cohort 3, respectively (Table 1). Kinetics of GMR CAR-T cells will be determined by quantifying the GMR CAR gene in the peripheral blood using real-time PCR after the CAR-T cell infusion. All the patients will be required to receive HSCT by day 56 following CAR-T cell infusion. The primary endpoint of the study is the safety, pharmacokinetics, and efficacy of GMR CAR-T therapy (Trial registration: jRCT2033210029).Conclusion: We herein described the protocol of first-in-human GMR CAR-T cells for relapsed/refractory myeloid malignancies. By employing the optimized CAR vector and production protocol, the safety and efficacy of GMR CAR-T cells will be evaluated in this study. [Display omitted] DisclosuresSaito: Toshiba corporation: Research Funding. Yagyu: AGC Inc.: Research Funding. Nakazawa: AGC Inc.: Research Funding; Toshiba Corporation: Research Funding.

Attenuated hematopoietic response to granulocyte-macrophage colony-stimulating factor in patients with acquired pulmonary alveolar proteinosis

The pathogenesis of acquired pulmonary alveolar proteinosis (PAP), a rare lung disease characterized by excessive surfactant accumulation within the alveolar space, remains obscure. Gene-targeted mice lacking the hematopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSF) or the signal-transducing beta-common chain of the GM-CSF receptor have impaired surfactant clearance and pulmonary pathology resembling human PAP. We therefore investigated the hematopoietic effects of GM-CSF in patients with PAP. The hematologic response of 5 infants with congenital PAP to 5 microgram/kg/d was of normal magnitude. By contrast, despite normal expression of GM-CSF receptor alpha- and beta-common chains on peripheral blood myelomonocytic cells (n = 6) and normal binding affinity of bone marrow mononuclear cells for GM-CSF (n = 3), each of the 12 patients with acquired PAP treated displayed impaired responses to GM-CSF; 5 microgram/kg/d produced only minor eosinophilia, and doses of 7.5 to 20 microgram/kg were required to induce >/=1.5-fold neutrophil increments in the 3 patients who underwent dose-escalation. However, neutrophilic responses to 5 microgram/kg granulocyte colony-stimulating factor (G-CSF) were normal (n = 4). In vitro, the proportion of hematopoietic progenitors responsive to GM-CSF (16.1% +/- 8.9%; P = .042) or interleukin-3 (IL-3; 19.3% +/- 7.7%; P = .063), both of which utilize the beta-common chain of the GM-CSF receptor complex, were reduced among patients with acquired PAP (n = 4) compared with normal bone marrow donor controls (47.2% +/- 25.9% and 40.9% +/- 18.6%, respectively). In the one individual who had complete resolution of lung disease during the period of study, this was temporally associated with correction of this defective in vitro response to GM-CSF and IL-3 on serial assessment. These data establish that patients with acquired PAP have an associated impaired responsiveness to GM-CSF that is potentially pathogenic in the development of their lung disease. Based on these observations, we propose a model of the pathogenesis of acquired PAP that suggests the disease arises as a consequence of an acquired clonal disorder within the hematopoietic progenitor cell compartment.

Engineered cell migration to lesions linked to autoimmune disease.

The damaging and degenerative effects in autoimmune diseases such as rheumatoid arthritis, multiple sclerosis and Crohn's disease often manifests as the formation of lesions that feature a high local concentration of granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF along with other pro-inflammatory factors form a positive feedback loop that ultimately perpetuate the lesions. Hence, to engineer chemotaxis to GM-CSF, we created a new chimeric GM-CSF receptor alpha subunit (GMRchi) that was coupled with a previously engineered Ca2+ -activated RhoA. When these proteins were expressed in mammalian cells, it allowed migration to chemical and cellular sources of GM-CSF. As a possible therapeutic intervention, we further implemented the mechanism of cell-cell membrane fusion and subsequent death. Since the microenvironment of lesions is more than just GM-CSF secretion, the further ability to recognize a combination of other features such as tissue markers will be needed for greater specificity. Nonetheless, this work represents a first step to enable cell-based therapy of autoimmune lesions.

Targeting the GM-CSF receptor for the treatment of CNS autoimmunity

In multiple sclerosis (MS), there is a growing interest in inhibiting the pro-inflammatory effects of granulocyte-macrophage colony-stimulating factor (GM-CSF). We sought to evaluate the therapeutic potential and underlying mechanisms of GM-CSF receptor alpha (Rα) blockade in animal models of MS. We show that GM-CSF signaling inhibition at peak of chronic experimental autoimmune encephalomyelitis (EAE) results in amelioration of disease progression. Similarly, GM-CSF Rα blockade in relapsing-remitting (RR)-EAE model prevented disease relapses and inhibited T cell responses specific for both the inducing and spread myelin peptides, while reducing activation of mDCs and inflammatory monocytes. In situ immunostaining of lesions from human secondary progressive MS (SPMS), but not primary progressive MS patients shows extensive recruitment of GM-CSF Rα+ myeloid cells. Collectively, this study reveals a pivotal role of GM-CSF in disease relapses and the benefit of GM-CSF Rα blockade as a potential novel therapeutic approach for treatment of RRMS and SPMS.

A randomised phase IIb study of mavrilimumab, a novel GM–CSF receptor alpha monoclonal antibody, in the treatment of rheumatoid arthritis

ObjectivesDespite the therapeutic value of current rheumatoid arthritis (RA) treatments, agents with alternative modes of action are required. Mavrilimumab, a fully human monoclonal antibody targeting the granulocyte–macrophage colony-stimulating factor receptor-α,...

Immortalized MH-S cells lack defining features of primary alveolar macrophages and do not support mouse pneumovirus replication

The SV-40-transformed MH-S cell line maintains some, but not all, features of primary alveolar macrophages (AMs) from BALB/c mice. We show here that MH-S cells produce inflammatory cytokines IL-6 and CXCL10 in response to challenge with Gram-positive Lactobacillus reuteri, and to TLR2 and NOD2 ligands Pam3CSK4 and MDP, respectively. In contrast, although wild-type AMs are infected in vivo by pneumonia virus of mice (PVM), no virus replication was detected in MH-S cells. Interestingly, the surface immunophenotype of MH-S cells (CD11c+Siglec F−) differs from that of wild-type AMs (CD11c+ Siglec F+) and is similar to that of immature AMs isolated from granulocyte macrophage-colony stimulating factor (GM-CSF) gene-deleted mice; AMs from GM-CSF−/− mice also support PVM replication. However, MH-S cells do not express the GM-CSF receptor alpha chain (CD116) and do not respond to GM-CSF. Due to these unusual features, MH-S cells should be used with caution as experimental models of AMs.

Cytokine refacing effect reduces granulocyte macrophage colony-stimulating factor susceptibility to antibody neutralization.

Crohn's Disease (CD) afflicts over half a million Americans with an annual economic impact exceeding $10 billion. Granulocyte macrophage colony-stimulating factor (GM-CSF) can increase patient immune responses against intestinal microbes that promote CD and has been effective for some patients in clinical trials. We have made important progress toward developing GM-CSF variants that could be more effective CD therapeutics by virtue of being less prone to neutralization by the endogenous GM-CSF autoantibodies that are highly expressed in CD patients. Yeast display engineering revealed mutations that increase GM-CSF variant binding affinity by up to ∼3-fold toward both GM-CSF receptor alpha and beta subunits in surface plasmon resonance experiments. Increased binding affinity did not reduce GM-CSF half-maximum effective concentration (EC50) values in conventional in vitro human leukocyte proliferation assays. Affinity-enhancing mutations did, however, promote a 'refacing effect' that imparted all five evaluated GM-CSF variants with increased in vitro bioactivity in the presence of GM-CSF-neutralizing polyclonal antisera. The most improved variant, H15L/R23L, was 6-fold more active than wild-type GM-CSF. Incorporation of additional known affinity-increasing mutations could augment the refacing effect and concomitant bioactivity improvements described here.

17: Structural and functional analysis of the GM-CSF:GM-CSF receptor alpha chain binary complex provide new insights into signalling of the GM-CSF ternary complex

Interleukin (IL)-3, granulocyte–macrophage colony stimulating factor (GM-CSF) and IL-5 are important cytokines that control production and function of myeloid cells and dendritic cells. Over-expression of these cytokines or their receptors can lead to chronic inflammatory diseases and myeloid leukaemias. These cytokines signal through heterodimeric specific receptors consisting of cytokine-specific α chains, and a signalling subunit β c, shared by all three receptors. We have determined the 3D crystal structure of the binary GM-CSF:GM-CSF receptor α chain (GMR α ) complex to 2.8 A resolution, which reveals for the first time all three extracellular domains of the GMR α receptor chain. The structure shows a striking resemblance to the related IL-3R α , IL-5R α and IL-13R α subunits; however, the differing positions of the N-terminal domains suggest that this domain may play a cytokine-specific role in cell signalling. We have used mutagenesis, ligand binding and functional studies to examine residues in GMR α and GM-CSF that define the binding interface, and identified residues involved in higher order complex assembly. Furthermore, the complete structure of the GMR α receptor chain from the binary complex was used to improve the electron density maps of the partial GMR α in the previously published ternary complex, elucidating additional GM-CSF:GMR α interactions and the position of the N-terminal domain of GMR α in the ternary complex. A structural comparison of the GM-CSF binary and ternary complexes revealed numerous major, as well as subtle, conformational changes in cytokine and both receptor chains. These studies enable us to identify differences and similarities in the way GM-CSF, IL-3 and IL-5 interact with their receptors and facilitate different types of cell signaling events.

Nonclinical safety of mavrilimumab, an anti-GMCSF receptor alpha monoclonal antibody, in cynomolgus monkeys: Relevance for human safety

Mavrilimumab (CAM-3001) is an investigational human IgG4 monoclonal antibody (MAb) targeting GM-CSF receptor alpha which is currently being developed for the treatment of RA. GM-CSF plays a central role in the pathogenesis of rheumatoid arthritis (RA) through the activation, differentiation, and survival of macrophages and neutrophils. To support clinical development, the nonclinical safety of mavrilimumab was evaluated in several studies with cynomolgus monkeys as the pharmacologically relevant species. Comprehensive toxicity parameters were assessed in each study, and treatment duration ranged from 4 to 26weeks. Mavrilimumab has an acceptable safety profile in monkeys with no changes in any parameters other than microscopic findings in lung. In several studies, minimal accumulation of foamy alveolar macrophages was observed. This finding was only seen in studies of at least 11weeks duration, was reversible following a dose-free recovery period and was considered non-adverse. At higher dose levels (≥30mg/kg/week), in a 26-week repeat-IV dose study, the presence of lung foreign material, cholesterol clefts, and granulomatous inflammation was also observed in a few animals and was considered adverse. The dose- and time-related accumulation of foamy macrophages in lung following exposure to mavrilimumab observed in several NHP studies was expected based upon the known role of GM-CSFRα signaling in the function of alveolar macrophages. Overall, a clean no-observed-adverse-effect-level (NOAEL) without any effects in lung was established and provided adequate clinical safety margins. In clinical studies in RA patients, mavrilimumab has demonstrated good clinical activity with adequate safety to support further clinical development. A Phase 2b study of mavrilimumab in subjects with RA is in progress.

Long-term follow-up and treatment of congenital alveolar proteinosis

BackgroundClinical presentation, diagnosis, management and outcome of molecularly defined congenital pulmonary alveolar proteinosis (PAP) due to mutations in the GM-CSF receptor are not well known.Case presentationA 2 1/2 years old girl was diagnosed as having alveolar proteinosis. Whole lung lavages were performed with a new catheter balloon technique, feasible in small sized airways. Because of some interstitial inflammation in the lung biopsy and to further improve the condition, empirical therapy with systemic steroids and azathioprin, and inhaled and subcutaneous GMCSF, were used. Based on clinical measures, total protein and lipid recovered by whole lung lavages, all these treatments were without benefit. Conversely, severe respiratory viral infections and an invasive aspergillosis with aspergilloma formation occurred. Recently the novel homozygous stop mutation p.Ser25X of the GMCSF receptor alpha chain was identified in the patient. This mutation leads to a lack of functional GMCSF receptor and a reduced response to GMCSF stimulation of CD11b expression of mononuclear cells of the patient. Subsequently a very intense treatment with monthly lavages was initiated, resulting for the first time in complete resolution of partial respiratory insufficiency and a significant improvement of the overall somato-psychosocial condition of the child.ConclusionsThe long term management from early childhood into young adolescence of severe alveolar proteinosis due to GMCSF receptor deficiency requires a dedicated specialized team to perform technically demanding whole lung lavages and cope with complications.

A Cell Free Assay System Estimating the Neutralizing Capacity of GM-CSF Antibody using Recombinant Soluble GM-CSF Receptor

BACKGROUNDS: Previously, we demonstrated that neutralizing capacity but not the concentration of GM-CSF autoantibody was correlated with the disease severity in patients with autoimmune pulmonary alveolar proteinosis (PAP)1-3. As abrogation of GM-CSF bioactivity in the lung is the likely cause for autoimmune PAP4,5, it is promising to measure the neutralizing capacity of GM-CSF autoantibodies for evaluating the disease severity in each patient with PAP. Until now, neutralizing capacity of GM-CSF autoantibodies has been assessed by evaluating the growth inhibition of human bone marrow cells or TF-1 cells stimulated with GM-CSF6-8. In the bioassay system, however, it is often problematic to obtain reliable data as well as to compare the data from different laboratories, due to the technical difficulties in maintaining the cells in a constant condition. OBJECTIVE: To mimic GM-CSF binding to GM-CSF receptor on the cell surface using cell-free receptor-binding-assay. METHODS: Transgenic silkworm technology was applied for obtaining a large amount for recombinant soluble GM-CSF receptor alpha (sGMRα) with high purity9-13. The recombinant sGMRα was contained in the hydrophilic sericin layers of silk threads without being fused to the silk proteins, and thus, we can easily extract from the cocoons in good purity with neutral aqueous solutions14,15. Fortunately, the oligosaccharide structures, which are critical for binding with GM-CSF, are more similar to the structures of human sGMRα than those produced by other insects or yeasts. RESULTS: The cell-free assay system using sGMRα yielded the data with high plasticity and reliability. GM-CSF binding to sGMRα was dose-dependently inhibited by polyclonal GM-CSF autoantibody in a similar manner to the bioassay using TF-1 cells, indicating that our new cell-free assay system using sGMRα is more useful for the measurement of neutralizing activity of GM-CSF autoantibodies than the bioassay system using TF-1 cell or human bone marrow cells. CONCLUSIONS: We established a cell-free assay quantifying the neutralizing capacity of GM-CSF autoantibody.

A Cell Free Assay System Estimating the Neutralizing Capacity of GM-CSF Antibody using Recombinant Soluble GM-CSF Receptor

Previously, we demonstrated that neutralizing capacity but not the concentration of GM-CSF autoantibody was correlated with the disease severity in patients with autoimmune pulmonary alveolar proteinosis (PAP)¹⁻³. As abrogation of GM-CSF bioactivity in the lung is the likely cause for autoimmune PAP⁴⁻⁵, it is promising to measure the neutralizing capacity of GM-CSF autoantibodies for evaluating the disease severity in each patient with PAP. Until now, neutralizing capacity of GM-CSF autoantibodies has been assessed by evaluating the growth inhibition of human bone marrow cells or TF-1 cells stimulated with GM-CSF⁶⁻⁸. In the bioassay system, however, it is often problematic to obtain reliable data as well as to compare the data from different laboratories, due to the technical difficulties in maintaining the cells in a constant condition. To mimic GM-CSF binding to GM-CSF receptor on the cell surface using cell-free receptor-binding-assay. Transgenic silkworm technology was applied for obtaining a large amount for recombinant soluble GM-CSF receptor alpha (sGMRα) with high purity⁹⁻¹³. The recombinant sGMRα was contained in the hydrophilic sericin layers of silk threads without being fused to the silk proteins, and thus, we can easily extract from the cocoons in good purity with neutral aqueous solutions¹⁴(,)¹⁵. Fortunately, the oligosaccharide structures, which are critical for binding with GM-CSF, are more similar to the structures of human sGMRα than those produced by other insects or yeasts. The cell-free assay system using sGMRα yielded the data with high plasticity and reliability. GM-CSF binding to sGMRα was dose-dependently inhibited by polyclonal GM-CSF autoantibody in a similar manner to the bioassay using TF-1 cells, indicating that our new cell-free assay system using sGMRα is more useful for the measurement of neutralizing activity of GM-CSF autoantibodies than the bioassay system using TF-1 cell or human bone marrow cells. We established a cell-free assay quantifying the neutralizing capacity of GM-CSF autoantibody.

Molecular basis of cytokine receptor activation

Cytokines are secreted soluble peptides that precisely regulate multiple cellular functions. Amongst these the GM-CSF/IL-3/IL-5 family of cytokines controls whether hematopoietic cells will survive or apoptose, proliferate, differentiate, migrate, or perform effector functions such as phagocytosis or reactive oxygen species release. Their potent and pleiotropic activities are mediated through binding to high affinity membrane receptors at surprisingly low numbers per cell. Receptor binding triggers a cascade of intracellular signaling events, including reversible phosphorylation of receptor subunits and associated signaling molecules, leading to multiple biological responses, with the prevention of apoptosis or "cell survival" being a key cellular function that underpins all others. Many chronic inflammatory diseases and a number of haematological malignancies are driven by deregulated GM-CSF, IL-3, or IL-5 cytokine receptor signaling, highlighting their importance in disease. A major step in understanding how these cytokine receptors function is to elucidate their three dimensional structure and to relate this to the many signaling pathways emanating from their receptors. We have recently solved the structure of the human GM-CSF receptor complexed to GM-CSF which revealed distinct forms of receptor assembly: a hexamer that comprises two molecules each of GM-CSF, GM-CSF receptor alpha chain and GM-CSF receptor beta chain; and an unexpected dodecamer in which two hexameric complexes associate through a novel site 4. This latter form is necessary to bring JAK2 molecules sufficiently close together to enable full receptor activation. In this review we focus on the most recent insights in cytokine receptor signaling, and in receptor assembly. The stage is now set to link distinct forms of cytokine receptor assembled structures to specific forms of cytokine receptor signaling and function. Armed with this knowledge it may be possible to map distinct cytokine receptor signaling pathways from the cell surface to the cell nucleus which may themselves become new therapeutic targets.

TGFβ inhibits GM‐CSF‐induced phosphorylation of ERK and MEK in human myeloid leukaemia cell lines via inhibition of phosphatidylinositol 3‐kinase (PI3‐k)

Activation of SMAD-independent p44/42 MAPK (ERK1/2) signalling by TGFbeta has been recently reported in various cell types. However, the mechanisms for the linkage between the SMAD-dependent and -independent pathways are poorly understood. In this study, we investigated whether TGF-beta activates the ERK pathway and how TGFbeta communicates with the MAP kinase signals induced by a mitogen, in human myeloid leukaemia cells. TGFbeta dramatically suppressed proliferation of MV4-11 and TF-1 cells without detectable phosphorylation of ERK1/2 and MEK1/2 for the duration of 48 h, as detected by MTT assay and Western blot analysis, respectively. In contrast, GM-CSF induced rapid and transient phosphorylation of MEK1/2 and ERK1/2 and up-regulated cell proliferation. Both GM-CSF-induced ERK1/2 activation and cell proliferation were significantly inhibited by TGFbeta. GM-CSF also induced transient phosphorylation of the p85 subunit of PI3-kinase. Corresponding to this change, phosphorylated p85 was found to bind to the GM-CSF receptor-alpha subunit, as detected by immunoprecipitation and Western blot analysis. PD98059, a selective inhibitor of MEK, blocked GM-CSF-induced phosphorylation of MEK and ERK but not p85. However, TGFbeta and LY294002, a potent inhibitor of PI3-kinase, significantly inhibited phosphorylation of both p85 and ERK1/2. These studies thus indicate that TGFbeta does not activate the ERK pathway but turns off the GM-CSF-induced ERK signal via inhibition of the PI3-kinase-Akt pathway, in these human leukaemia cells.

In vitro affinity maturation of human GM-CSF antibodies by targeted CDR-diversification

The mammalian immune system applies somatic hypermutation to select for antibodies with improved dissociation rates in vivo up to an intrinsic limit, previously termed as affinity ceiling. However, for certain therapeutic applications it may be desirable to further improve antibody affinities beyond that limit. In this study the selection of antibodies specific for the pro-inflammatory cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) from the HuCAL GOLD human antibody library is described. In order to increase affinity and also functional activity, in vitro affinity maturation of a pool of lead Fab candidates was carried out. CDR-L3 and parallel CDR-H2 diversification using trinucleotide consensus cassettes were followed by the combination of optimized CDR-L3 and CDR-H2 leading to a 5000-fold improved affinity finally reaching a K D of 400 fM. Cytokine neutralizing potential of MOR04357 was evaluated in a TF-1 proliferation assay. Along with affinity optimization a 2000-fold increase in potency was observed compared to the parental antibody. Due to species cross-reactivity MOR04357 also blocks rat GM-CSF induced proliferation of FDCP-1 cells. Receptor inhibition studies showed that MOR04357 prevents the interaction of GM-CSF with the GM-CSF receptor alpha chain. As a consequence this leads to a blockade in signal transduction as measured by abolished STAT5 phosphorylation in the presence of GM-CSF and antibody. Due to its pro-inflammatory role GM-CSF has been implicated in the pathophysiology of inflammatory diseases like rheumatoid arthritis or asthma. Based on the mode of action described herein MOR04357 shows favourable antibody features as a potential drug candidate.

Role of the cytokine environment and cytokine receptor expression on the generation of functionally distinct dendritic cells from human monocytes

Myeloid dendritic cells (DC) and macrophages evolve from a common precursor. However, factors controlling monocyte differentiation toward DC or macrophages are poorly defined. We report that the surface density of the GM-CSF receptor (GM-CSFR) alpha subunit in human peripheral blood monocytes varies among donors. Although no correlation was found between the extent of GM-CSFR and monocyte differentiation into DC driven by GM-CSF and IL-4, GM-CSFR expression strongly influenced the generation of CD1a(+) dendritic-like cells in the absence of IL-4. CD1a(+) cells generated in the presence of GM-CSF express CD40, CD80, MHC class I and II, DC-SIGN, MR, CCR5, and partially retain CD14 expression. Interestingly, they spontaneously induce the expansion of CD4(+) and CD8(+) allogeneic T lymphocytes producing IFN-gamma, and migrate toward CCL4 and CCL19. Upon stimulation with TLR ligands, they acquire the phenotypic features of mature DC. In contrast, the allostimulatory capacity is not further increased upon LPS activation. However, by blocking LPS-induced IL-10, a higher T cell proliferative response and IL-12 production were observed. Interestingly, IL-23 secretion was not affected by endogenous IL-10. These results highlight the importance of GM-CSFR expression in monocytes for cytokine-induced DC generation and point to GM-CSF as a direct player in the generation of functionally distinct DC.

Gene expression profiling of peripheral mononuclear cells in lame dairy cows with foot lesions

Lameness is a major health issue and likely the single most common cause of pain and discomfort in dairy cattle. Appropriate treatment is delayed or neglected due, in part, to lack of reliable detection. Assessment of cows with lameness is currently limited to subjective visual scoring systems based on locomotion and posture abnormalities. These systems are unreliable to detect lameness, and therefore, a large number of cows remain undiagnosed. The objective of this research was to search for potential biomarkers for lameness-associated painful inflammatory foot lesions in dairy cattle using microarray-based gene expression profiling of peripheral blood mononuclear cells (PBMC). BOTL5 microarrays spotted in duplicate with cDNA representing bovine immune response genes were interrogated with cDNA samples in an eight-array, balanced complete block design with dye swap. Samples from eight lame cows with inflammatory foot lesions and from eight sound cows were pair-matched by age, weight, days in lactation, and pregnancy status at time of PBMC collection and directly compared with each other on individual arrays. Statistical analysis of resulting fluorescence intensity data revealed 31 genes that were putatively differentially expressed in lame versus sound cows ( P < 0.05). Of these, BLASTn analysis and gene ontology information showed that 28 genes had high similarity or homology to known human and/or rodent genes. Validation of 15 of these genes known to be important in inflammation and pain was carried out using relative quantitative real-time RT-PCR, which confirmed the up-regulation of interleukin (IL)-2 (12.68 ± 1.47-fold increase) and IL-10 (2.39 ± 0.55-fold increase), matrix metalloproteinase-13 (MMP-13) (10.44 ± 1.14-fold increase), and chemokine C–C motif receptor-5 (CCR5) (5.26 ± 1.05-fold increase), in lame relative to sound cows ( P ≤ 0.05). Similarly, granulocyte-macrophage colony-stimulating factor receptor alpha chain precursor (GM-CSF-R-alpha) (2.30 ± 0.63-fold increase) and IL-4 (2.06 ± 0.59-fold increase) showed a tendency ( P = 0.10) for up-regulation in lame compared to sound cows. PBMC co-expression of IL-2, MMP-13, CCR5 and IL-10, and potentially IL-4 and GM-CSF-R-alpha appears to be a promising, objective sign of lameness-related inflammatory foot lesions in dairy cattle. In conclusion, this study revealed potential biomarkers of the presence of foot lesions that could boost diagnostic accuracy of lameness and, ultimately, help identify animals in need of pain relief.

Expression of PU.1 and terminal differentiation of alveolar macrophages in newborn rats

PU.1, which is a transcription factor, promotes the terminal differentiation of alveolar macrophages (AMs). Its expression is regulated by granulocyte/macrophage colony-stimulating factor (GM-CSF). In this study of AMs in newborn rats, we performed immunohistochemical staining, acid phosphatase staining, reverse transcriptase polymerase chain reaction (RT-PCR), quantitative real-time PCR, cytokine assay, and electron microscopy. AMs at 3 and 7 days after birth had a large foamy appearance with an intracytoplasmic accumulation of surfactants. Weak expression of PU.1 was observed in the nuclei. AMs at 15 days after birth were smaller, and PU.1 expression had increased. Ultrastructurally, AMs at 1 day after birth had a smooth surface and abundant lamellar structures in the cytoplasm, whereas AMs at 56 days after birth were characterized by (1) abundant microvillar projections on the cell surface, and (2) well-developed lysosomes and a few lamellar structures in the cytoplasm. Acid phosphatase activity and the expression of mannose receptor, scavenger receptor, and GM-CSF receptor alpha were enhanced in AMs with time after birth. These results suggest that AMs are initially immature, and that their terminal differentiation starts after birth concomitantly with an increased expression of PU.1.

Phenotyping of Neoplastic (CD34+/CD38−/CD123+) Stem Cells in Myeloid Malignancies Reveals Expression of Multiple Molecular Targets.

Recent data suggest that myeloid neoplasms are organized hierarchically in terms of self renewal and maturation of early progenitor cells, similar to normal myelopoiesis. In acute myeloid leukemia (AML), the NOD/SCID mouse-repopulating leukemic stem cells usually co-express CD123 with CD34, but lack CD38. So far, however, little is known about expression of other markers and targets on these progenitors. In the present study, expression of target antigens on CD34+/CD38− cells was analyzed by multicolor flow cytometry in patients with AML (n=18), myelodysplastic syndromes (MDS, n=6), chronic myeloid leukemia (CML, n=8), systemic mastocytosis (SM, n=9), and normal bone marrow (n=5). The IL-3Ra chain (CD123) was found to be expressed on CD34+/CD38− cells in a majority of all patients in all disease-categories. Independent of the type of disease, the vast majority of these stem cells also co-expressed aminopeptidase-N (CD13) and the target receptor CD44 in all patients. CD34+/CD38− progenitor cells expressed variable amounts of the Mylotarg® receptor CD33, KIT (CD117), HLA-DR, and AC133 (CD133). With regard to AC133, two distinct subpopulations of progenitor cells were detected in many cases, namely a CD133+ and a clearly CD133- cell-fraction. In patients with AML, the levels of CD33 varied from patient to patient with a broad range of reactivity, whereas in most patients with MDS, CML, and SM, CD33 was found to be consistently expressed on most progenitors. In most patients, neoplastic stem cells did not express substantial amounts of the GM-CSF receptor alpha chain (CD116), Thy-1 (CD90), E-NPP3 (CD203c), MDR-1 (CD243), or PAR-2. In the normal bone marrow, CD34+/CD38− cells co-expressed CD13, CD44 and CD45, but did not express CD33, CD116, or CD123. In conclusion, neoplastic stem cells in various myeloid neoplasms appear to express a similar phenotype including target receptors such as CD13, CD33, and CD44. These antigens may thus be attractive targets of therapy in AML. However, since many of these targets are not expressed on all stem cells in all patients, the elimination of the entire clone may require combinations of targeted antibodies or use of additional drugs. In other cases (CD13, CD44, CD45), the target antigen is also expressed on normal stem cells, so that targeted therapy is likely to be an ablative maneuver and thus would require a combined stem cell transplantation approach.

Detection of differentiation‐ and activation‐linked cell surface antigens on cultured mast cell progenitors

Mast cells (MC) are multifunctional effector cells of the immune system. They derive from uncommitted CD34(+) hemopoietic progenitor cells (HPC). Depending on the stage of maturation and the environment, MC variably express differentiation- and activation-linked antigens. Little is known, however, about the regulation of expression of such antigens in immature human MC. We analyzed expression of CD antigens on human MC grown from cord blood-derived CD34(+) HPC. The HPC were isolated by magnetic cell sorting (MACS) and FACS to >97% purity, and were cultured in stem cell factor (SCF) and interleukin (IL)-6 with or without additional cytokines (IL-4 or IL-10) in serum-free medium. The cell surface phenotype of MC was determined by monoclonal antibodies and flow cytometry. Cultured MC progenitors were found to react with antibodies against various CD antigens including CD58, CD63, CD117, CD147, CD151, CD203c, and CD172a, independent of the growth factors used and time-point investigated (days 14-42). CD116 [granulocyte-macrophage colony-stimulating factor receptor alpha (GM-CSFRalpha)] and CD123 (IL-3Ralpha) were expressed on MC precursors on day 14, but disappeared thereafter. Cultured MC did not express CD2, CD3, CD5, CD10, CD19, or CD25. Addition of IL-10 to MC cultures showed no effect on expression of CD antigens. However, IL-4 was found to promote expression of CD35 and CD88 on cultured MC without changing expression of other CD antigens. Most MC antigens may already be expressed at an early stage of mastopoiesis. Whereas IL-3R and GM-CSFRs are lost during differentiation of MC, these cells may acquire complement receptors (CD35, CD88) under the influence of distinct cytokines.