Transient Kupffer cell depletion and subsequent replacement by infiltrating monocyte-derived cells does not alter the induction or progression of hepatocellular carcinoma.

Due to a combination of rapid disease progression and the lack of curative treatment options, hepatocellular carcinoma (HCC) is one of the deadliest cancers worldwide. Infiltrated, monocyte-derived, tumor-associated macrophages are known to play a role in HCC pathogenesis, but the involvement of Kupffer cells (KCs) remains elusive. Here, we used the Clec4F-diphteria toxin receptor transgenic mouse model to specifically investigate the effect of KC depletion on HCC initiation, progression and neoplastic growth following liver resection. For this purpose, several HCC mouse models with varying underlying etiologies were used and partial hepatectomy was performed. Our results show that in HCC, developed on a fibrotic or non-alcoholic steatohepatitis background, depletion of embryonic KCs at the onset of HCC induction and the subsequent replacement by monocyte-derived KCs does not affect the tumor burden, tumor microenvironment or the phenotype of isolated KCs at end-stage disease. In non-chronic liver disease-associated diethylnitrosamine-induced HCC, ablation of Clec4F+ KCs did not alter tumor progression or neoplastic growth following liver resection. Our results show that temporal ablation of resident KCs does not impact HCC pathogenesis, neither in the induction phase nor in advanced disease, and indicate that bone marrow-derived KCs are able to swiftly repopulate the available KC niche and adopt their phenotype.

Immunotherapy for visceral leishmaniasis: A trapeze of balancing counteractive forces.

The protozoan parasite Leishmania donovani, residing and replicating within the cells of the monocyte-macrophage (mono-mac) lineage, causes visceral leishmaniasis (VL) in humans. While, Leishmania infantum, is the main causative agent for zoonotic VL, where dogs are the main reservoirs of the disease. The chemotherapy is a serious problem because of restricted repertoire of drugs, drug-resistant parasites, drug-toxicity and the requirement for parenteral administration, which is a problem in resource-starved countries. Moreover, immunocompromised individuals, particularly HIV-1 infected are at higher risk of VL due to impairment in T-helper cell and regulatory cell responses. Furthermore, HIV-VL co-infected patients report poor response to conventional chemotherapy. Recent efforts are therefore directed towards devising both prophylactic and therapeutic immunomodulation. As far as prophylaxis is concerned, although canine vaccines for the disease caused by Leishmania infantum or Leishmania chagasi are available, no vaccine is available for use in humans till date. Therefore, anti-leishmanial immunotherapy triggering or manipulating the host's immune response is gaining momentum during the last two decades. Immunomodulators comprised of small molecules, anti-leishmanial peptides, complex ligands for host receptors, cytokines or their agonists and antibodies have been given trials both in experimental models and in humans. However, the success of immunotherapy in humans remains a far-off target. We, therefore, propose that devising a successful immunotherapy is an act of balancing enhanced beneficial Leishmania-specific responses and deleterious immune activation/hyperinflammation just as the swings in a trapeze.

IRF8 is a Reliable Monoblast Marker for Acute Monocytic Leukemias.

Blast evaluation in patients with acute monocytic leukemias (AMoL) is notoriously difficult due to the lack of reliable surface markers and cytologic subtleties on the aspirate smears. While blasts of most nonmonocytic acute leukemias express CD34, available immunohistochemical antibodies to monocytic blasts also mark normal background mature monocytes. We searched for a potential biomarker candidate by surveying specific gene expression profiles of monocyte progenitors. Our investigations led us to IRF8, which is a lineage-specific transcription factor critical for the production of monocytic and dendritic cell progenitors. In this study, we tested and validated a monoclonal antibody to IRF8 as a novel immunohistochemical stain for trephine core biopsies of human bone marrow. We assessed the expression of IRF8 in 90 cases of AMoL, including posttherapy staging bone marrows, 23 cases of chronic myelomonocytic leukemia, 26 cases of other acute myeloid leukemia subtypes, and 18 normal control marrows. In AMoL, there was high correlation of IRF8-positive cells to aspirate blast count (R=0.95). Comparison of IRF8 staining to aspirate blast percentage in chronic myelomonocytic leukemia also showed good correlation (R=0.86). In contrast, IRF8-positive cells did not correlate with blast count in other subtypes of acute myeloid leukemia (R=0.56) and staining was <5% in all normal control marrows, even those with reactive monocytosis. We found that IRF8 was also weakly reactive in B cells and hematogones, with the latter accounting for rare cases of discrepancies. When IRF8 was used to categorize cases as AMoL, positive for residual leukemia or negative, the sensitivity was 98%, specificity was 82%, positive predictive value was 86%, and negative predictive value was 98%. These results demonstrate that IRF8 may serve as a clinically useful immunostain to diagnose and track AMoLs on bone marrow core biopsies. This can be particularly impactful in the setting of poor aspiration and focal blast increase. In the era of new targeted therapies that have been reported to induce monocytic outgrowths of leukemia, a marker for malignant monoblasts may prove even more critical.

An Antibody-Drug Conjugate That Selectively Targets Human Monocyte Progenitors for Anti-Cancer Therapy.

As hematopoietic progenitors supply a large number of blood cells, therapeutic strategies targeting hematopoietic progenitors are potentially beneficial to eliminate unwanted blood cells, such as leukemic cells and immune cells causing diseases. However, due to their pluripotency, targeting those cells may impair the production of multiple cell lineages, leading to serious side effects such as anemia and increased susceptibility to infection. To minimize those side effects, it is important to identify monopotent progenitors that give rise to a particular cell lineage. Monocytes and monocyte-derived macrophages play important roles in the development of inflammatory diseases and tumors. Recently, we identified human monocyte-restricted progenitors, namely, common monocyte progenitors and pre-monocytes, both of which express high levels of CD64, a well-known monocyte marker. Here, we introduce a dimeric pyrrolobenzodiazepine (dPBD)-conjugated anti-CD64 antibody (anti-CD64-dPBD) that selectively induces the apoptosis of proliferating human monocyte-restricted progenitors but not non-proliferating mature monocytes. Treatment with anti-CD64-dPBD did not affect other types of hematopoietic cells including hematopoietic stem and progenitor cells, neutrophils, lymphocytes and platelets, suggesting that its off-target effects are negligible. In line with these findings, treatment with anti-CD64-dPBD directly killed proliferating monocytic leukemia cells and prevented monocytic leukemia cell generation from bone marrow progenitors of chronic myelomonocytic leukemia patients in a patient-derived xenograft model. Furthermore, by depleting the source of monocytes, treatment with anti-CD64-dPBD ultimately eliminated tumor-associated macrophages and significantly reduced tumor size in humanized mice bearing solid tumors. Given the selective action of anti-CD64-dPBD on proliferating monocyte progenitors and monocytic leukemia cells, it should be a promising tool to target cancers and other monocyte-related inflammatory disorders with minimal side effects on other cell lineages.

Estrogens decrease osteoclast number by attenuating mitochondria oxidative phosphorylation and ATP production in early osteoclast precursors.

Loss of estrogens at menopause is a major cause of osteoporosis and increased fracture risk. Estrogens protect against bone loss by decreasing osteoclast number through direct actions on cells of the myeloid lineage. Here, we investigated the molecular mechanism of this effect. We report that 17ß-estradiol (E2) decreased osteoclast number by promoting the apoptosis of early osteoclast progenitors, but not mature osteoclasts. This effect was abrogated in cells lacking Bak/Bax-two pro-apoptotic members of the Bcl-2 family of proteins required for mitochondrial apoptotic death. FasL has been previously implicated in the pro-apoptotic actions of E2. However, we show herein that FasL-deficient mice lose bone mass following ovariectomy indistinguishably from FasL-intact controls, indicating that FasL is not a major contributor to the anti-osteoclastogenic actions of estrogens. Instead, using microarray analysis we have elucidated that ERα-mediated estrogen signaling in osteoclast progenitors decreases "oxidative phosphorylation" and the expression of mitochondria complex I genes. Additionally, E2 decreased the activity of complex I and oxygen consumption rate. Similar to E2, the complex I inhibitor Rotenone decreased osteoclastogenesis by promoting osteoclast progenitor apoptosis via Bak/Bax. These findings demonstrate that estrogens decrease osteoclast number by attenuating respiration, and thereby, promoting mitochondrial apoptotic death of early osteoclast progenitors.

Concordance among hematopathologists in classifying blasts plus promonocytes: A bone marrow pathology group study.

Enumeration of blasts and promonocytes is essential for World Health Organization (WHO) classification of myelomonocytic neoplasms. The accuracy of distinguishing blasts, promonocytes and monocytes, including normal vs abnormal monocytes, remains controversial. The objective of this analysis is to assess concordances between experienced hematopathologists in classifying cells as blasts, promonocytes, and monocytes according to WHO criteria. Each of 11 hematopathologists assessed glass slides from 20 patients [12 with chronic myelomonocytic leukemia (CMML) and 8 with acute myeloid leukemia (AML)] including blood and BM aspirate smears, and limited nonspecific esterase (NSE) stains. All cases were blindly reviewed. Fleiss' extension of Cohen's kappa for multiple raters was used on these variables, separately for peripheral blood (PB) and bone marrow (BM). Spearman's rank correlation was used to assess correlations between each pair of hematopathologists for each measurement. For the classification based on the sum of blasts and promonocytes in the BM, Fleiss' kappa was estimated as 0.744. For PB, categorizing patients according to the sum of blasts and promonocytes, Fleiss' kappa was estimated as 0.949. Distinction of abnormal monocytes from normal monocytes in PB did not achieve a good concordance and showed strong evidence of differences between hematopathologists (P < .0001). The hematopathologists achieved a good concordance rate of 74% in CMML vs AML classification and a high k rate, confirming that criteria for defining the blasts equivalents (blasts plus promonocytes) could be applied consistently. Identification of monocyte subtypes (abnormal vs normal) was not concordant. Our results support the practice of combining blasts/promonocytes into a single category.

Inflammatory macrophage derived TNFα downregulates estrogen receptor α via FOXO3a inactivation in human breast cancer cells.

Patients with estrogen receptor α positive (ERα+) breast cancer can respond to endocrine therapy, but treatment resistance is common and associated with downregulation of ERα expression in the dormant residual cells. Here we show, using long-term NSG xenograft models of human breast cancer and primary human monocytes, in vitro primary cell cultures and tumors from breast cancer patients, that macrophage derived tumor necrosis factor alpha (TNFα) downregulates ERα in breast cancer cells via inactivation of the transcription factor Forkhead box O transcription factor 3a (FOXO3a). Moreover, presence of tumor associated macrophages in the primary tumor of breast cancer patients, was associated with ERα negativity, and with worse prognosis in patients with ERα+ tumors. We propose that pro-inflammatory macrophages, despite being tumoricidal, may have direct effects on tumor progression and endocrine resistance in breast cancer patients. Our findings suggest that TNFα antagonists should be evaluated for treatment of ERα+ breast cancer.

JNK1 regulates RANKL-induced osteoclastogenesis via activation of a novel Bcl-2-Beclin1-autophagy pathway.

JNK1 plays an important role in osteoclastogenesis in response to the osteoclastogenic cytokine receptor activator for nuclear factor-κB ligand (RANKL). JNK1 is widely accepted as an autophagy regulator under stress conditions. However, the role of JNK1-mediated autophagy in osteoclastogenesis remains largely unknown. In the current study, our data showed that JNK1 inhibition by a pharmacological inhibitor or RNA interference significantly reduced the autophagic response induced by RANKL in osteoclast precursors (OCPs) derived from bone marrow-derived macrophages. Overexpression of the key autophagy protein Beclin1 rescued autophagy deficiency and osteoclastogenesis in the presence of a JNK inhibitor (SP600125). In contrast, JNK activator (anisomycin)-induced autophagy was blocked by Beclin1 knockdown in OCPs. In addition, JNK1 inhibition increased apoptosis and blocked autophagy, whereas overexpression of Beclin1 reversed the enhanced apoptosis induced by JNK1 inhibition in OCPs. Furthermore, RANKL could induce the phosphorylation of Bcl-2, subsequently dissociating Beclin1 from the Bcl-2-Beclin1 complex, which could be blocked by JNK1 inhibition. Collectively, this study revealed that JNK1 regulated osteoclastogenesis by activating Bcl-2-Beclin1-autophagy signaling in addition to the classic c-Jun/activator protein 1 pathway, which provided the first evidence for the contribution of JNK1 signaling to OCP autophagy and the autophagic mechanism underlying JNK1-regulated osteoclastogenesis. An important osteoclastogenesis-regulating signaling pathway (JNK1-Bcl-2-Beclin1-autophagy activation) was identified, which provides novel potential targets for the clinical therapy of metabolic bone diseases.-Ke, D., Ji, L., Wang, Y., Fu, X., Chen, J., Wang, F., Zhao, D., Xue, Y., Lan, X., Hou, J. JNK1 regulates RANKL-induced osteoclastogenesis via activation of a novel Bcl-2-Beclin1-autophagy pathway.

Different monocyte phenotypes result in proresolving macrophages in conjugated linoleic acid-induced attenuated progression and regression of atherosclerosis.

Monocytes/macrophages drive progression and regression of atherosclerosis. Conjugated linoleic acid (CLA), an anti-inflammatory lipid, mediates atheroprotective effects. We investigated how CLA alters monocyte/macrophage phenotype during attenuated progression and regression of atherosclerosis. Apolipoprotein E knockout (ApoE-/-) mice were fed a high-fat (60%) high-cholesterol (1%) diet (HFHCD) for 2 wk, followed by 6-wk 1% CLA 80:20 supplementation to investigate disease progression. Simultaneously, ApoE-/- mice were fed a 12-wk HFHCD with/without CLA for the final 4 wk to investigate regression. Aortic lesions were quantified by en face staining. Proteomic analysis, real-time quantitative PCR and flow cytometry were used to interrogate monocyte/macrophage phenotypes. CLA supplementation inhibited atherosclerosis progression coincident with decreased proinflammatory and increased anti-inflammatory macrophages. However, CLA-induced regression was associated with increased proinflammatory monocytes resulting in increased proresolving M2 bone marrow-derived macrophages, splenic macrophages, and dendritic cells in lesion-draining lymph nodes. Proteomic analysis confirmed regulation of a proinflammatory bone marrow response, which was abolished upon macrophage differentiation. Thus, in attenuation and regression of atherosclerosis, regardless of the monocyte signature, during monocyte to macrophage differentiation, proresolving macrophages prevail, mediating vascular repair. This study provides novel mechanistic insight into the monocyte/macrophage phenotypes in halted atherosclerosis progression and regression of atherosclerosis.-Bruen, R., Curley, S., Kajani, S., Lynch, G., O'Reilly, M. E., Dillon, E. T., Fitzsimons, S., Mthunzi, L., McGillicuddy, F. C., Belton, O. Different monocyte phenotypes result in proresolving macrophages in conjugated linoleic acid-induced attenuated progression and regression of atherosclerosis.

Hyaluronan preconditioning of monocytes/macrophages affects their angiogenic behavior and regulation of TSG-6 expression in a tumor type-specific manner.

Hyaluronan is a glycosaminoglycan normally present in the extracellular matrix in most tissues. Hyaluronan is a crucial player in many processes associated with cancer, such as angiogenesis, invasion, and metastasis. However, little has been reported regarding the action of hyaluronan on monocytes/macrophages (Mo/MØ) in tumor angiogenesis and its consequences on tumor development. In the present study, we investigated the effects of hyaluronan of different sizes on human Mo/MØ angiogenic behavior in colorectal and breast carcinoma. In vitro, the treatment of Mo/MØ with lysates and conditioned media from a breast but not from colorectal carcinoma cell line plus high-molecular weight hyaluronan induced: (a) an increased expression of angiogenic factors VEGF, IL-8, FGF-2, and MMP-2, (b) an increased endothelial cell migration, and (c) a differential expression of hyaluronan-binding protein TSG-6. Similar results were observed in Mo/MØ derived from breast cancer patients treated with tumor lysates. Besides, macrophages primed with high-molecular weight hyaluronan and inoculated in human breast cancer xenograft tumor increased blood vessel formation and diminished TSG-6 levels. In contrast, the effects triggered by high-molecular weight hyaluronan on Mo/MØ in breast cancer context were not observed in the context of colorectal carcinoma. Taken together, these results indicate that the effect of high-molecular weight hyaluronan as an inductor of the angiogenic behavior of macrophages in breast tumor context is in part consequence of the presence of TSG-6.

Single-cell analysis of fate-mapped macrophages reveals heterogeneity, including stem-like properties, during atherosclerosis progression and regression.

Atherosclerosis is a leading cause of death worldwide in industrialized countries. Disease progression and regression are associated with different activation states of macrophages derived from inflammatory monocytes entering the plaques. The features of monocyte-to-macrophage transition and the full spectrum of macrophage activation states during either plaque progression or regression, however, are incompletely established. Here, we use a combination of single-cell RNA sequencing and genetic fate mapping to profile, for the first time to our knowledge, plaque cells derived from CX3CR1+ precursors in mice during both progression and regression of atherosclerosis. The analyses revealed a spectrum of macrophage activation states with greater complexity than the traditional M1 and M2 polarization states, with progression associated with differentiation of CXC3R1+ monocytes into more distinct states than during regression. We also identified an unexpected cluster of proliferating monocytes with a stem cell-like signature, suggesting that monocytes may persist in a proliferating self-renewal state in inflamed tissue, rather than differentiating immediately into macrophages after entering the tissue.

BCG-induced formation of neutrophil extracellular traps play an important role in bladder cancer treatment.

Bacillus Calmette-Guerin (BCG) is one of the most effective treatments for bladder cancer. Little attention has been paid to the possible role of neutrophils in BCG immunotherapy. In this study, we examined neutrophil extracellular traps (NETs) formation induced by BCG stimulation, and found that BCG-induced NETs exerted cytotoxicity, induced apoptosis and cell-cycle arrest, and inhibited migration in bladder tumor cells. BCG-activated tumor cells but not non-activated ones elicited NETs formation, in which IL-8 and TNF-α from activated tumor cells both took effect. Moreover, NETs activated peripheral blood mononuclear cells (PBMCs) exhibited a higher expression of CD4 and Th1 cytokines. Additionally, the role of NETs in vivo contributed to the recruitment of T cells and monocytes-macrophages and tissue damage, thus preventing tumor growth. NETs proteins mainly caused these effects on tumor and cellular immunity. In conclusion, we demonstrated a novel immunoregulatory role for NETs in the early stages of BCG immunotherapy.

Deletion of myeloid IRS2 enhances adipose tissue sympathetic nerve function and limits obesity.

OBJECTIVE: Sympathetic nervous system and immune cell interactions play key roles in the regulation of metabolism. For example, recent convergent studies have shown that macrophages regulate obesity through brown adipose tissue (BAT) activation and beiging of white adipose tissue (WAT) via effects upon local catecholamine availability. However, these studies have raised issues about the underlying mechanisms involved including questions regarding the production of catecholamines by macrophages, the role of macrophage polarization state and the underlying intracellular signaling pathways in macrophages that might mediate these effects. METHODS: To address such issues we generated mice lacking Irs2, which mediates the effects of insulin and interleukin 4, specifically in LyzM expressing cells (Irs2LyzM-/- mice). RESULTS: These animals displayed obesity resistance and preservation of glucose homeostasis on high fat diet feeding due to increased energy expenditure via enhanced BAT activity and WAT beiging. Macrophages per se did not produce catecholamines but Irs2LyzM-/- mice displayed increased sympathetic nerve density and catecholamine availability in adipose tissue. Irs2-deficient macrophages displayed an anti-inflammatory transcriptional profile and alterations in genes involved in scavenging catecholamines and supporting increased sympathetic innervation. CONCLUSIONS: Our studies identify a critical macrophage signaling pathway involved in the regulation of adipose tissue sympathetic nerve function that, in turn, mediates key neuroimmune effects upon systemic metabolism. The insights gained may open therapeutic opportunities for the treatment of obesity.

M2C Polarization by Baicalin Enhances Efferocytosis via Upregulation of MERTK Receptor.

Baicalin is the main active ingredient primary isolated from the Chinese herb, Scutellaria baicalensis Georgi. Although baicalin can induce M2 macrophage polarization, we still do not know the subtype of macrophages polarized by baicalin. In this study, we characterized that murine bone marrow derived macrophages induced by M-CSF can be further polarized into M2C phenotype by baicalin. The signatures of M2C macrophages for mRNA expression like interferon regulatory factor 4 (IRF4), interleukin-10 (IL-10), MERTK and PTX3 were up-regulated. Moreover, we observed the concomitantly decreasing of tumor necrosis factor alpha (TNF- α ), interferon regulatory factor 5 (IRF5), IL-6. In contrast, M2 macrophages polarized by IL-4 increased gene transcript of arginase-1 (Arg-1) and surface marker of CD206 indicates that their identity as M2A rather than M2C subtypes. Interestingly, the phagocytosis as well as efferocytosis activity were significantly enhanced in M2C macrophage polarized by baicalin and these capacities were associated with the expression of MERTK receptor. Finally, we conclude that baicalin induced M2C macrophages polarization with both elevations of efferocytosis and anti-inflammatory activity.

High-Dimensional Analysis Delineates Myeloid and Lymphoid Compartment Remodeling during Successful Immune-Checkpoint Cancer Therapy.

Although current immune-checkpoint therapy (ICT) mainly targets lymphoid cells, it is associated with a broader remodeling of the tumor micro-environment. Here, using complementary forms of high-dimensional profiling, we define differences across all hematopoietic cells from syngeneic mouse tumors during unrestrained tumor growth or effective ICT. Unbiased assessment of gene expression of tumor-infiltrating cells by single-cell RNA sequencing (scRNAseq) and longitudinal assessment of cellular protein expression by mass cytometry (CyTOF) revealed significant remodeling of both the lymphoid and myeloid intratumoral compartments. Surprisingly, we observed multiple subpopulations of monocytes/macrophages, distinguishable by the markers CD206, CX3CR1, CD1d, and iNOS, that change over time during ICT in a manner partially dependent on IFNγ. Our data support the hypothesis that this macrophage polarization/activation results from effects on circulatory monocytes and early macrophages entering tumors, rather than on pre-polarized mature intratumoral macrophages.

The role of autophagy in survival response induced by 27-hydroxycholesterol in human promonocytic cells.

Autophagy has been shown to be stimulated in advanced atherosclerotic plaques by metabolic stress, inflammation and oxidized lipids. The lack of published studies addressing the potential stimulation of pro-survival autophagy by oxysterols, a family of cholesterol oxidation products, has prompted our study. Thus, the goal of the current study is to elucidate the molecular mechanism of the autophagy induced by 27-hydroxycholesterol (27-OH), that is one of the most abundant oxysterols in advanced atherosclerotic lesions, and to assess whether the pro-oxidant effect of the oxysterol is involved in the given response. Here we showed that 27-OH, in a low micromolar range, activates a pro-survival autophagic response in terms of increased LC3 II/LC3 I ratio and Beclin 1, that depends on the up-regulation of extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Akt pathways as a potential result of an intracellular reactive oxygen species increase provoked by the oxysterol in human promonocytic U937 cells. Moreover, 27-OH induced autophagy is dependent on the relation between nuclear factor erythroid 2 p45-related factor 2 (Nrf2)-dependent antioxidant response and p62. The data obtained highlight the involvement of cholesterol oxidation products in the pathogenesis of oxidative stress related chronic diseases like atherosclerosis. Therefore, deeply understanding the complex mechanism and generating synthetic or natural molecules targeting this survival mechanism might be very promising tools in the prevention of such diseases.

Developmental control of macrophage function.

The combination between novel fate-mapping tools and single-cell RNA-sequencing technology has revealed the presence of multiple macrophage progenitors. This raises the fascinating possibility that what was once perceived as immense functional plasticity of macrophages could in fact come down to separate macrophage subsets performing distinct functions because of their differential cellular origin. The question of macrophage plasticity versus macrophage heterogeneity is broader than the difference between macrophages of embryonic or adult hematopoietic origin and is particularly relevant in the context of inflammation. In this manuscript, we review the potential impact of cellular origin on the function of macrophages. We also highlight the need for novel 'functional fate-mapping' tools that would reveal the history of the functional state of macrophages, rather than their cellular origin, in order to finally study their true plasticity in vivo.

Phenotypic stability and plasticity in GMP-derived cells as determined by their underlying regulatory network.

Motivation: Blood cell formation has been recognized as a suitable system to study celular differentiation mainly because of its experimental accessibility, and because it shows characteristics such as hierarchical and gradual bifurcated patterns of commitment, which are present in several developmental processes. Although hematopoiesis has been extensively studied and there is a wealth of molecular and cellular data about it, it is not clear how the underlying molecular regulatory networks define or restrict cellular differentiation processes. Here, we infer the molecular regulatory network that controls the differentiation of a blood cell subpopulation derived from the granulocyte-monocyte precursor (GMP), comprising monocytes, neutrophils, eosinophils, basophils and mast cells. Results: We integrate published qualitative experimental data into a model to describe temporal expression patterns observed in GMP-derived cells. The model is implemented as a Boolean network, and its dynamical behavior is studied. Steady states of the network can be clearly identified with the expression profiles of monocytes, mast cells, neutrophils, basophils, and eosinophils, under wild-type and mutant backgrounds. Availability and implementation: All scripts are publicly available at https://github.com/caramirezal/RegulatoryNetworkGMPModel. Contact: lmendoza@biomedicas.unam.mx. Supplementary information: Supplementary data are available at Bioinformatics online.