Gene expression screening of human mast cells and eosinophils using high-density oligonucleotide probe arrays: abundant expression of major basic protein in mast cells

Characterization of human umbilical cord blood-derived mast cells using high-throughput expression profiling and next-generation knowledge discovery platforms

Mast cells (MCs) are tissue-resident innate immune cells that express the high-affinity receptor for immunoglobulin E and are responsible for host defense and an array of diseases related to immune system. We aimed in this study to characterize the pathways and gene signatures of human cord blood-derived MCs (hCBMCs) in comparison to cells originating from CD34- progenitors using next-generation knowledge discovery methods. CD34+ cells were isolated from human umbilical cord blood using magnetic activated cell sorting and differentiated into MCs with rhIL-6 and rhSCF supplementation for 6-8 weeks. The purity of hCBMCs was analyzed by flow cytometry exhibiting the surface markers CD117+CD34-CD45-CD23-FcεR1αdim. Total RNA from hCBMCs and CD34- cells were isolated and hybridized using microarray. Differentially expressed genes were analyzed using iPathway Guide and Pre-Ranked Gene Set Enrichment Analysis. Next-generation knowledge discovery platforms revealed MC-specific gene signatures and molecular pathways enriched in hCBMCs and pertain the immunological response repertoire.

ACDC: a general approach for detecting phenotype or exposure associated co-expression

Background

Existing module-based differential co-expression methods identify differences in gene-gene relationships across phenotype or exposure structures by testing for consistent changes in transcription abundance. Current methods only allow for assessment of co-expression variation across a singular, binary or categorical exposure or phenotype, limiting the information that can be obtained from these analyses.

Methods

Here, we propose a novel approach for detection of differential co-expression that simultaneously accommodates multiple phenotypes or exposures with binary, ordinal, or continuous data types.

Results

We report an application to two cohorts of asthmatic patients with varying levels of asthma control to identify associations between gene co-expression and asthma control test scores. Results suggest that both expression levels and covariances of ADORA3, ALOX15, and IDO1 are associated with asthma control.

Conclusion

ACDC is a flexible extension to existing methodology that can detect differential co-expression across varying external variables.

Comprehensive Analysis of Nasal Polyps Reveals a More Pronounced Type 2 Transcriptomic Profile of Epithelial Cells and Mast Cells in Aspirin-Exacerbated Respiratory Disease

Chronic rhinosinusitis with nasal polyps is affecting up to 3% of Western populations. About 10% of patients with nasal polyps also suffer from asthma and intolerance to aspirin, a syndrome called aspirin-exacerbated respiratory disease. Although eosinophilic inflammation is predominant in polyps of both diseases, phenotypic differences in the tissue-derived microenvironment, elucidating disease-specific characteristics, have not yet been identified. We sought to obtain detailed information about phenotypic and transcriptional differences in epithelial and immune cells in polyps of aspirin-tolerant and intolerant patients. Cytokine profiles in nasal secretions and serum of patients suffering from aspirin-exacerbated respiratory disease (n = 10) or chronic rhinosinusitis with nasal polyps (n = 9) were assessed using a multiplex mesoscale discovery assay. After enrichment for immune cell subsets by flow cytometry, we performed transcriptomic profiling by employing single-cell RNA sequencing. Aspirin-intolerant patients displayed significantly elevated IL-5 and CCL17 levels in nasal secretions corresponding to a more pronounced eosinophilic type 2 inflammation. Transcriptomic profiling revealed that epithelial and mast cells not only complement one another in terms of gene expression associated with the 15-lipoxygenase pathway but also show a clear type 2-associated inflammatory phenotype as identified by the upregulation of POSTN, CCL26, and IL13 in patients with aspirin-exacerbated respiratory disease. Interestingly, we also observed cellular stress responses indicated by an increase of MTRNR2L12, MTRNR2L8, and NEAT1 across all immune cell subsets in this disease entity. In conclusion, our findings support the hypothesis that epithelial and mast cells act in concert as potential drivers of the pathogenesis of the aspirin-exacerbated respiratory disease.

Low-dose mepolizumab is effective as an add-on therapy for treating long-lasting peripheral neuropathy in patients with eosinophilic granulomatosis with polyangiitis

OBJECTIVE

To assess the effectiveness of low-dose mepolizumab as an add-on therapy for treating peripheral neurological symptoms in eosinophilic granulomatosis with polyangiitis (EGPA).

METHODS

We prospectively studied 13 EGPA patients with conventional treatment-resistant peripheral neuropathy. Their symptoms (pain, numbness, and muscle weakness) were assessed on a visual analogue scale (VAS) before and after 12 months of mepolizumab therapy (100 mg every 4 weeks). Peripheral eosinophil levels and several biomarkers including urinary levels of eosinophil-derived neurotoxin (EDN) were measured before and after therapy.

RESULTS

VAS scores for pain and numbness significantly improved after 12 months of mepolizumab therapy (from 67.0 to 48.0, P = 0.012, and from 67.0 to 51.0, P = 0.017, respectively). However, the VAS score for muscle weakness did not improve (P = 0.36). There were significant correlations between treatment-related changes in urinary EDN levels from baseline to 6 months later and percent changes in the VAS scores of pain and numbness (r = 0.75, P = 0.020; r = 0.88, P = 0.002).

CONCLUSIONS

Treatment-resistant peripheral neuropathy in EGPA was significantly improved by low-dose mepolizumab, and effectiveness was correlated with decreased urinary EDN. Because the possibility of a placebo effect cannot be formally excluded, placebo-controlled studies will be required in the future.

Eosinophil-mediated inflammation in the absence of eosinophilia

The increase of eosinophil levels is a hallmark of type-2 inflammation. Blood eosinophil counts act as a convenient biomarker for asthma phenotyping and the selection of biologics, and they are even used as a prognostic factor for severe coronavirus disease 2019. However, the circulating eosinophil count does not always reflect tissue eosinophilia and vice versa. The mismatch of blood and tissue eosinophilia can be seen in various clinical settings. For example, blood eosinophil levels in patients with acute eosinophilic pneumonia are often within normal range despite the marked symptoms and increased number of eosinophils in bronchoalveolar lavage fluid. Histological studies using immunostaining for eosinophil granule proteins have revealed the extracellular deposition of granule proteins coincident with pathological conditions, even in the absence of a significant eosinophil infiltrate. The marked deposition of eosinophil granule proteins in tissue is often associated with cytolytic degranulation. Recent studies have indicated that extracellular trap cell death (ETosis) is a major mechanism of cytolysis. Cytolytic ETosis is a total cell degranulation in which cytoplasmic and nuclear contents, including DNA and histones that act as alarmins, are also released. In the present review, eosinophil-mediated inflammation in such mismatch conditions is discussed.

Increased mast cell density is associated with decreased fibrosis in human atrial tissue

Fibrotic remodelling of the atria is poorly understood and can be regulated by myocardial immune cell populations after injury. Mast cells are resident immune sentinel cells present in the heart that respond to tissue damage and have been linked to fibrosis in other settings. The role of cardiac mast cells in fibrotic remodelling in response to human myocardial injury is controversial. In this study, we sought to determine the association between mast cells, atrial fibrosis, and outcomes in a heterogeneous population of cardiac surgical patients, including a substantial proportion of coronary artery bypass grafting patients. Atrial appendage from patients was assessed for collagen and mast cell density by histology and by droplet digital polymerase chain reaction (ddPCR) for mast cell associated transcripts. Clinical variables and outcomes were also followed. Mast cells were detected in human atrial tissue at varying densities. Histological and ddPCR assessment of mast cells in atrial tissue were closely correlated. Patients with high mast cell density had less fibrosis and lower severity of heart failure classification or incidence mortality than patients with low mast cell content. Analysis of a homogeneous population of coronary artery bypass graft patients yielded similar observations. Therefore, evidence from this study suggests that increased atrial mast cell populations are associated with decreased clinical cardiac fibrotic remodelling and improved outcomes, in cardiac surgery patients.

Linker histone H1.2 and H1.4 affect the neutrophil lineage determination

Neutrophils are important innate immune cells that tackle invading pathogens with different effector mechanisms. They acquire this antimicrobial potential during their maturation in the bone marrow, where they differentiate from hematopoietic stem cells in a process called granulopoiesis. Mature neutrophils are terminally differentiated and short-lived with a high turnover rate. Here, we show a critical role for linker histone H1 on the differentiation and function of neutrophils using a genome-wide CRISPR/Cas9 screen in the human cell line PLB-985. We systematically disrupted expression of somatic H1 subtypes to show that individual H1 subtypes affect PLB-985 maturation in opposite ways. Loss of H1.2 and H1.4 induced an eosinophil-like transcriptional program, thereby negatively regulating the differentiation into the neutrophil lineage. Importantly, H1 subtypes also affect neutrophil differentiation and the eosinophil-directed bias of murine bone marrow stem cells, demonstrating an unexpected subtype-specific role for H1 in granulopoiesis.

Detection of Mast Cells Expressing c-Kit Using Antibody Covalently Bound to Gelatin Elongated from Surface of Immunosensor Based on Surface Plasmon Resonance

An immunosensor based on surface plasmon resonance was applied to detect mast cells expressing c-Kit. Sufficient detection of the mast cells was achieved by covalent immobilization of gelatin firstly on the sensor surface and followed by covalent binding of the anti-c-Kit antibody to lysine residues in the gelatin molecules through bis(sulfosuccinimidyl)suberate (BS3) treatment. By using BS3, which is a homo-bifunctional reagent, the lysine residues of the anti-c-Kit antibody easily bound to the lysine residues of the gelatin in the physiological condition. The lower limit of detection was 10⁴ cells/mL.

Novel eosinophilic gene expression networks associated with IgE in two distinct asthma populations

BACKGROUND

Asthma represents a significant public health burden; however, novel biological therapies targeting immunoglobulin E (IgE)-mediated pathways have widened clinical treatment options for the disease.

OBJECTIVE

In this study, we sought to identify gene transcripts and gene networks involved in the determination of serum IgE levels in people with asthma that can help inform the development of novel therapeutic agents.

METHODS

We analysed gene expression data from a cross-sectional study of 326 Costa Rican children with asthma, aged 6 to 12 years, from the Genetics of Asthma in Costa Rica Study and 610 young adults with asthma, aged 16 to 25 years, from the Childhood Asthma Management Program trial. We utilized differential gene expression analysis and performed weighted gene coexpression network analysis on 25 060 genes, to identify gene transcripts and network modules associated with total IgE, adjusting for age and gender. We used pathway enrichment analyses to identify key biological pathways underlying significant modules. We compared findings that replicated between both populations.

RESULTS

We identified 31 transcripts associated with total IgE that replicated between the two study cohorts. These results were notable for increased eosinophil-related transcripts (including IL5RA, CLC, SMPD3, CCL23 and CEBPE). Pathway enrichment identified the regulation of T cell tolerance as important in the determination of total IgE levels, supporting a key role for IDO1.

CONCLUSIONS AND CLINICAL RELEVANCE

These results provide robust evidence that biologically meaningful gene expression profiles (relating to eosinophilic and regulatory T cell pathways in particular) associated with total IgE levels can be identified in individuals diagnosed with asthma during childhood. These profiles and their constituent genes may represent novel therapeutic targets.

Lysophosphatidylserine receptor P2Y10: A G protein-coupled receptor that mediates eosinophil degranulation

BACKGROUND

P2Y10, along with GPR34 and GPR174, is a G protein-coupled receptor that is activated by an endogenous lipid mediator lysophosphatidylserine (LysoPS). Its expression pattern and its function are completely unknown. We have previously shown that P2Y10 is one of the highly up-regulated genes at the late differentiation stage during in vitro eosinophilopoiesis.

OBJECTIVE

We explored the expression and functions of P2Y10 in human cord blood (CB)-derived and peripheral blood (PB) eosinophils.

METHODS

Real-time PCR, FACS, Western blot, ELISA, and chemotaxis assays were performed to determine the expression and function of P2Y10.

RESULTS

As CB cells differentiated towards eosinophils, P2Y10 mRNA and protein were abundantly expressed. P2Y10 was the most highly expressed in the granulocytes from PB, to a lesser extent in monocytes, and least in lymphocytes. Further fractionation of granulocytes revealed that eosinophils express P2Y10 much more strongly than do neutrophils. PB eosinophils solely expressed P2Y10 among the three LysoPS receptors, while PB neutrophils expressed the three at comparable levels. LysoPS activated both CB and PB eosinophils to induce a robust ERK phosphorylation. Importantly, LysoPS was capable of triggering degranulation of ECP in PB eosinophils. This response was significantly reduced by pharmacological inhibitors of TNF-alpha-converting enzyme (TACE), epidermal growth factor receptor (EGFR), and ERK1/2, which were known to be required in P2Y10-mediated signalling pathways. However, LysoPS had no effect on chemotaxis, differentiation, or eosinophil survival.

CONCLUSIONS AND CLINICAL RELEVANCE

LysoPS provokes eosinophil degranulation through P2Y10. Therefore, P2Y10 is a potential therapeutic target to control eosinophil-associated diseases.

Terminally Differentiating Eosinophils Express Neutrophil Primary Granule Proteins as well as Eosinophil-specific Granule Proteins in a Temporal Manner

Neutrophils and eosinophils, 2 prominent granulocytes, are commonly derived from myelocytic progenitors through successive stages in the bone marrow. Our previous genome-wide transcriptomic data unexpectedly showed that genes encoding a multitude of neutrophil primary granule proteins (NPGPs) were markedly downregulated during the end period of eosinophilic terminal differentiation when cord blood (CB) cluster of differentiation (CD) 34⁺ cells were induced to differentiate toward the eosinophil lineage during a 24-day culture period. Accordingly, this study aimed to examine whether NPGP genes were expressed on the way to eosinophil terminal differentiation stage and to compare their expression kinetics with that of genes encoding eosinophil-specific granule proteins (ESGPs). Transcripts of all NPGP genes examined, including proteinase 3, myeloperoxidase, cathepsin G (CTSG), and neutrophil elastase, reached a peak at day 12 and sharply declined thereafter, while transcript of ESGP genes including major basic protein 1 (MBP1) attained maximum expression at days 18 or 24. Growth factor independent 1 (GFI1) and CCAAT/enhancer-binding protein α (C/EBPA), transactivators for the NPGP genes, were expressed immediately before the NPGP genes, whereas expression of C/EBPA, GATA1, and GATA2 kinetically paralleled that of eosinophil granule protein genes. The expression kinetics of NPGPs and ESGPs were duplicated upon differentiation of the eosinophilic leukemia cell line (EoL-1) immature eosinophilic cells. Importantly, confocal image analysis showed that CTSG was strongly coexpressed with MBP1 in differentiating CB eosinophils at days 12 and 18 and became barely detectable at day 24 and beyond. Our results suggest for the first time the presence of an immature stage where eosinophils coexpress NPGPs and ESGPs before final maturation.

Frontline Science: Eosinophil-deficient MBP-1 and EPX double-knockout mice link pulmonary remodeling and airway dysfunction with type 2 inflammation

Eosinophils and the release of cationic granule proteins have long been implicated in the development of the type 2-induced pathologies linked with respiratory inflammation. Paradoxically, the ablation of the two genes encoding the most abundant of these granule proteins, major basic protein-1 (MBP-1) and eosinophil peroxidase (EPX), results in a near collapse of eosinophilopoiesis. The specificity of this lineage ablation and the magnitude of the induced eosinopenia provide a unique opportunity to clarify the importance of eosinophils in acute and chronic inflammatory settings, as well as to identify potential mechanism(s) of action linked with pulmonary eosinophils in those settings. Specifically, we examined these issues by assessing the induced immune responses and pathologies occurring in MBP-1^-/-/EPX^-/- mice after 1) ovalbumin sensitization/provocation in an acute allergen-challenge protocol, and 2) crossing MBP-1^-/-/EPX^-/- mice with a double-transgenic model of chronic type 2 inflammation (i.e., I5/hE2). Acute allergen challenge and constitutive cytokine/chemokine expression each induced the accumulation of pulmonary eosinophils in wild-type controls that was abolished in the absence of MBP-1 and EPX (i.e., MBP-1^-/-/EPX^-/- mice). The expression of MBP-1 and EPX was also required for induced lung expression of IL-4/IL-13 in each setting and, in turn, the induced pulmonary remodeling events and lung dysfunction. In summary, MBP-1^-/-/EPX^-/- mice provide yet another definitive example of the immunoregulatory role of pulmonary eosinophils. These results highlight the utility of this unique strain of eosinophil-deficient mice as part of in vivo model studies investigating the roles of eosinophils in health and disease settings.

Mast cells in asthma--state of the art

Mast cells (MCs) play a central role in tissue homoeostasis, sensing the local environment through numerous innate cell surface receptors. This enables them to respond rapidly to perceived tissue insults with a view to initiating a co-ordinated programme of inflammation and repair. However, when the tissue insult is chronic, the ongoing release of multiple pro-inflammatory mediators, proteases, cytokines and chemokines leads to tissue damage and remodelling. In asthma, there is strong evidence of ongoing MC activation, and their mediators and cell-cell signals are capable of regulating many facets of asthma pathophysiology. This article reviews the evidence behind this.

IL-22BP is produced by eosinophils in human gut and blocks IL-22 protective actions during colitis

Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel diseases (IBDs), are characterized by high levels of IL-22 production. Rodent studies revealed that this cytokine is protective during colitis but whether this is true in IBDs is unclear. We show here that levels of the soluble inhibitor of IL-22, interleukin 22-binding protein (IL-22BP), are significantly enhanced during IBDs owing to increased numbers of IL-22BP-producing eosinophils, that we unexpectedly identify as the most abundant source of IL-22BP protein in human gut. In addition, using IL-22BP-deficient rats, we confirm that endogenous IL-22BP is effective at blocking protective actions of IL-22 during acute colitis. In conclusion, our study provides new important insights regarding the biology of IL-22 and IL-22BP in the gut and indicates that protective actions of IL-22 are likely to be suboptimal in IBDs thus making IL-22BP a new relevant therapeutic target.

Gene expression profiles in chronic idiopathic (spontaneous) urticaria

BACKGROUND

The pathophysiology of chronic idiopathic (spontaneous) urticaria (CIU) is poorly understood.

OBJECTIVE

We hypothesized that a study of gene expression in active lesions from patients with CIU would uncover unexpected associations.

METHODS

We enrolled eight patients with CIU and six healthy controls, and obtained 4 mm punch biopsy specimens of active lesions and unaffected skin of patients with CIU and of skin from normal controls. Routine histologic evaluation was performed, RNA was isolated, and gene expression data were assessed. Due to technical reasons, the final evaluation included six samples of lesional skin, six samples of nonlesional skin, and five samples of normal skin.

RESULTS

As expected, lesional skin had more inflammatory cells per high-powered field (mean ± SE, 96 ± 6) than did samples from nonlesional skin of the subjects with CIU (17 ± 2) (p < 0.01). Lesions of CIU showed significant upregulation of 506 genes and reduced expression of 51 genes. Those most upregulated were predominantly involved in cell adhesion (e.g., selectin E [SELE]), cell activation (e.g., CD69), and chemotaxis (e.g., CCL2). Twelve independent canonical pathways with p ≤ 0.001 were identified (including intracellular kinase pathways (RAs-related nuclear protein [RAN] and Janus activated kinase/interferon), cytokine signaling pathways (IL-9, IL10, and IFN), a strong inflammatory response (interferon, IL-9, IL-10, inducible nitric oxide synthase and glucocorticoid pathways) and increased cell proliferation (RAN signaling, cell cycle control, and tRNA charging).

CONCLUSIONS

This preliminary study describes a method to study gene activation in urticarial lesions and demonstrated a strong inflammatory response with a large variety of activated genes that are distinct from those reported with other dermatologic conditions.

Paul Ehrlich's mastzellen: a historical perspective of relevant developments in mast cell biology

Following the discovery of mast cells (or mastzellen) by the prolific physician researcher, Paul Ehrlich, many advances have improved our understanding of these cells and their fascinating biology. The discovery of immunoglobulin E and receptors for IgE and IgG on mast cells heralded further in vivo and in vitro studies, using molecular technologies and gene knockout models. Mast cells express an array of inflammatory mediators including tryptase, histamine, cytokines, chemokines, and growth factors. They play a role in many varying disease states, from atopic diseases, parasitic infections, hematological malignancies, and arthritis to osteoporosis. This review will attempt to summarize salient evolving areas in mast cell research over the last few centuries that have led to our current understanding of this pivotal multifunctional cell.

Targeting gene expression during the early bone healing period in the mandible: A base for bone tissue engineering

PURPOSE

Although bone tissue engineering techniques have become more and more sophisticated than in the past, natural bone healing mechanisms have not been sufficiently considered for further improvement of these techniques so far. We used an established animal model with transcriptome analysis to generate an unbiased picture of early bone healing to support tissue engineering concepts.

MATERIAL AND METHODS

In 30 Wistar rats, a 3-mm bone defect was created in the mandibular angle. Tissue was sampled at 5, 10, and 15 days, and the former defect area was excised to undergo transcriptome analysis after RNA extraction. Five differentially expressed genes were further evaluated with reverse transcription-polymerase chain reaction (rt-PCR).

RESULTS

Transcriptome analysis revealed 2467 significantly over- and under-expressed transcripts after 5 days and 2265 after 15 days of bone healing, respectively. Validation via rt-PCR confirmed overexpression of osteoactivin, angiopoietin-like factor-4, and metallomatrix proteinase-9 and underexpression of mastcellprotease-10 and proteoglycane-2 in comparison to values in the control group.

CONCLUSION

This systematic genome-wide transcriptome analysis helps to decipher the physiological mechanisms behind physiological bone healing. The exemplary depiction of 5 genes demonstrates the great complexity of metabolic processes during early bone healing. Here, BMP-2 signaling pathways and local hypoxia play decisive roles in bone formation.

Dendritic cell-bound IgE functions to restrain allergic inflammation at mucosal sites

Antigen-mediated cross-linking of Immunoglobulin E (IgE) bound to mast cells/basophils via FcɛRI, the high affinity IgE Fc-receptor, is a well-known trigger of allergy. In humans, but not mice, dendritic cells (DCs) also express FcɛRI that is constitutively occupied with IgE. In contrast to mast cells/basophils, the consequences of IgE/FcɛRI signals for DC function remain poorly understood. We show that humanized mice that express FcɛRI on DCs carry IgE like non-allergic humans and do not develop spontaneous allergies. Antigen-specific IgE/FcɛRI cross-linking fails to induce maturation or production of inflammatory mediators in human DCs and FcɛRI-humanized DCs. Furthermore, conferring expression of FcɛRI to DCs decreases the severity of food allergy and asthma in disease-relevant models suggesting anti-inflammatory IgE/FcɛRI signals. Consistent with the improved clinical parameters in vivo, antigen-specific IgE/FcɛRI cross-linking on papain or lipopolysaccharide-stimulated DCs inhibits the production of pro-inflammatory cytokines and chemokines. Migration assays confirm that the IgE-dependent decrease in cytokine production results in diminished recruitment of mast cell progenitors; providing a mechanistic explanation for the reduced mast cell-dependent allergic phenotype observed in FcɛRI-humanized mice. Our study demonstrates a novel immune regulatory function of IgE and proposes that DC-intrinsic IgE signals serve as a feedback mechanism to restrain allergic tissue inflammation.

Superantigenic Yersinia pseudotuberculosis induces the expression of granzymes and perforin by CD4+ T cells

Bacterial superantigens (SAgs) are immunostimulatory toxins that induce acute diseases mainly through the massive release of inflammatory cytokines. Yersinia pseudotuberculosis is the only Gram-negative bacterium known to produce a SAg (Y. pseudotuberculosis-derived mitogen [YPM]). This SAg binds major histocompatibility complex class II molecules on antigen-presenting cells and T cell receptors (TcR) bearing the variable region Vβ3, Vβ9, Vβ13.1, or Vβ13.2 (in humans) and Vβ7 or Vβ8 (in mice). We have previously shown that YPM exacerbates the virulence of Y. pseudotuberculosis in mice. With a view to understanding the mechanism of YPM's toxicity, we compared the immune response in BALB/c mice infected with a YPM-producing Y. pseudotuberculosis or the corresponding isogenic, SAg-deficient mutant. Five days after infection, we observed strong CD4(+) Vβ7(+) T cell expansion and marked interleukin-4 (IL-4) production in mice inoculated with SAg-producing Y. pseudotuberculosis. These phenomena were correlated with the activation of ypm gene transcription in liver and spleen. A transcriptomic analysis revealed that the presence of YPM also increased expression of granzyme and perforin genes in the host's liver and spleen. This expression was attributed to a CD4(+) T cell subset, rather than to natural killer T (NKT) cells that display a TcR with a Vβ region that is potentially recognized by YPM. Increased production of cytotoxic molecules was correlated with hepatotoxicity, as demonstrated by an increase in plasma alanine aminotransferase activity. Our results demonstrate that YPM activates a potentially hepatotoxic CD4(+) T cell population.

Expression levels of eosinophil granule protein mRNAs in induced sputum reflect airway hyperresponsiveness and airflow limitation

Eosinophils are regarded as the major effector cells that produce symptoms in allergic diseases. Activation of eosinophils induces extracellular release of a number of eosinophil granule proteins, including major basic protein (MBP), eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), and eosinophil-derived neurotoxin. The objective of this study was to evaluate the differences and significance of the sputum eosinophil% and expression levels of eosinophilic granule protein mRNAs in allergic airway disease. Induced sputum samples were obtained from non-smokers with 25 asthma, 54 eosinophilic bronchitis, 16 allergic rhinitis, and 19 healthy control subjects. The eosinophil granule protein mRNAs were measured with real time RT-PCR. There was no correlation between the sputum eosinophil% and the mRNA level of any of eosinophil granule proteins. However, the expression levels of MBP and ECP mRNAs were higher in subjects with each of the specified allergic diseases than those in control subjects (P < 0.05). Moreover, in the subjects with allergic sensitization, the expression levels of MBP and EPO mRNAs were significantly higher in those with airway hyperresponsiveness (13 subjects) than in those without airway hyperresponsiveness (32 subjects) (P = 0.004 and 0.010, respectively). In asthma patients, the FEV1% was negatively correlated with ECP mRNA levels (r = -0.510, P = 0.022), but showed no correlation with sputum eosinophil%. In conclusion, mRNA levels of eosinophil granule proteins, rather than sputum eosinophil%, may reflect airway hyperresponsiveness and airflow limitation. In practice, consideration for the eosinophil% as well as the eosinophil granule proteins levels in induced sputum is needed.

Transcription factor GATA1 is dispensable for mast cell differentiation in adult mice

Although previous studies have shown that GATA1 is required for mast cell differentiation, the effects of the complete ablation of GATA1 in mast cells have not been examined. Using conditional Gata1 knockout mice (Gata1(-/y)), we demonstrate here that the complete ablation of GATA1 has a minimal effect on the number and distribution of peripheral tissue mast cells in adult mice. The Gata1(-/y) bone marrow cells were capable of differentiating into mast cells ex vivo. Microarray analyses showed that the repression of GATA1 in bone marrow mast cells (BMMCs) has a small impact on the mast cell-specific gene expression in most cases. Interestingly, however, the expression levels of mast cell tryptases in the mouse chromosome 17A3.3 were uniformly reduced in the GATA1 knockdown cells, and GATA1 was found to bind to a 500-bp region at the 5' end of this locus. Revealing a sharp contrast to that observed in the Gata1-null BMMCs, GATA2 deficiency resulted in a significant loss of the c-Kit(+) FcεRIα(+) mast cell fraction and a reduced expression of several mast cell-specific genes. Collectively, GATA2 plays a more important role than GATA1 in the regulation of most mast cell-specific genes, while GATA1 might play specific roles in mast cell functions.

GATA1s induces hyperproliferation of eosinophil precursors in Down syndrome transient leukemia

Transient leukemia (TL) is evident in 5–10% of all neonates with Down syndrome (DS) and associated with N-terminal truncating GATA1-mutations (GATA1s). Here we report that TL cell clones generate abundant eosinophils in a substantial fraction of patients. Sorted eosinophils from patients with TL and eosinophilia carried the same GATA1s-mutation as sorted TL-blasts, consistent with their clonal origin. TL-blasts exhibited a genetic program characteristic of eosinophils and differentiated along the eosinophil lineage in vitro. Similarly, ectopic expression of Gata1s, but not Gata1, in wild-type CD34⁺-hematopoietic stem and progenitor cells induced hyperproliferation of eosinophil promyelocytes in vitro. While GATA1s retained the function of GATA1 to induce eosinophil genes by occupying their promoter regions, GATA1s was impaired in its ability to repress oncogenic MYC and the pro-proliferative E2F transcription network. ChIP-seq indicated reduced GATA1s occupancy at the MYC promoter. Knockdown of MYC, or the obligate E2F-cooperation partner DP1, rescued the GATA1s-induced hyperproliferative phenotype. In agreement, terminal eosinophil maturation was blocked in Gata1^Δe2 knockin mice, exclusively expressing Gata1s, leading to accumulation of eosinophil precursors in blood and bone marrow. These data suggest a direct relationship between the N-terminal truncating mutations of GATA1 and clonal eosinophilia in DS patients.

Eosinophil peroxidase in sputum represents a unique biomarker of airway eosinophilia

BACKGROUND

Sputum eosinophilia has been shown to be a predictor of response to anti-eosinophil therapies in patients with airway diseases. However, quantitative cell counts and differentials of sputum are labor intensive. The objective of this study was to validate a novel ELISA-based assay of eosinophil peroxidase (EPX) in sputum as a rapid and reliable marker of airway eosinophils.

METHODS

The utility of EPX-based ELISA as an eosinophil-specific assay was achieved through comparisons with sputum eosinophil differential counts in freshly prepared and archived patient samples from a variety of clinical settings.

RESULTS

EPX levels in sputum correlated with eosinophil percentage (r(s) = 0.84) in asthma patients with varying degrees of airway eosinophilia. Significantly, unlike assays of other eosinophil granule proteins (e.g., ECP and EDN), which often detect the presence of these proteins even in asthma patients with neutrophilic bronchitis, EPX-based ELISA levels are not increased in this subset of asthma patients or in COPD patients lacking evidence of an airway eosinophilia. Moreover, sputum EPX was a surrogate marker of airway eosinophilia in other patient studies (e.g., allergen inhalation and treatment trials the anti-(IL-5) therapeutic Mepolizumab™). Finally, EPX levels in cytocentrifuged prepared sputum supernatants correlated with those from rapidly prepared noncentrifuged filtrates of sputum (r(s) = 0.94).

CONCLUSION AND CLINICAL IMPLICATION

EPX-based ELISA is a valid, reliable, repeatable, and specific surrogate marker of eosinophils and/or eosinophil degranulation in the sputum of respiratory patients. The novel EPX assay is a valid and reproducible eosinophil-specific assay that can potentially be developed into a point-of-care assessment of eosinophil activity in airway secretions.

Identification of genes expressed by human airway eosinophils after an in vivo allergen challenge

Background

The mechanism for the contribution of eosinophils (EOS) to asthma pathophysiology is not fully understood. Genome-wide expression analysis of airway EOS by microarrays has been limited by the ability to generate high quality RNA from sufficient numbers of airway EOS.

Objective

To identify, by genome-wide expression analyses, a compendium of expressed genes characteristic of airway EOS following an in vivo allergen challenge.

Methods

Atopic, mild asthmatic subjects were recruited for these studies. Induced sputum was obtained before and 48h after a whole lung allergen challenge (WLAC). Individuals also received a segmental bronchoprovocation with allergen (SBP-Ag) 1 month before and after administering a single dose of mepolizumab (anti-IL-5 monoclonal antibody) to reduce airway EOS. Bronchoalveolar lavage (BAL) was performed before and 48 h after SBP-Ag. Gene expression of sputum and BAL cells was analyzed by microarrays. The results were validated by qPCR in BAL cells and purified BAL EOS.

Results

A total of 299 transcripts were up-regulated by more than 2-fold in total BAL cells following SBP-Ag. Mepolizumab treatment resulted in a reduction of airway EOS by 54.5% and decreased expression of 99 of the 299 transcripts. 3 of 6 post-WLAC sputum samples showed increased expression of EOS-specific genes, along with the expression of 361 other genes. Finally, the intersection of the 3 groups of transcripts (increased in BAL post SBP-Ag (299), decreased after mepolizumab (99), and increased in sputum after WLAC (365)) was composed of 57 genes characterizing airway EOS gene expression.

Conclusion

We identified 57 genes that were highly expressed by BAL EOS compared to unseparated BAL cells after in vivo allergen challenge. 41 of these genes had not been previously described in EOS and are thus potential new candidates to elucidate EOS contribution to airway biology.

Human versus mouse eosinophils: "that which we call an eosinophil, by any other name would stain as red"

The respective life histories of human subjects and mice are well defined and describe a unique story of evolutionary conservation extending from sequence identity within the genome to the underpinnings of biochemical, cellular, and physiologic pathways. As a consequence, the hematopoietic lineages of both species are invariantly maintained, each with identifiable eosinophils. This canonical presence nonetheless does not preclude disparities between human and mouse eosinophils, their effector functions, or both. Indeed, many books and reviews dogmatically highlight differences, providing a rationale to discount the use of mouse models of human eosinophilic diseases. We suggest that this perspective is parochial and ignores the wealth of available studies and the consensus of the literature that overwhelming similarities (and not differences) exist between human and mouse eosinophils. The goal of this review is to summarize this literature and in some cases provide experimental details comparing and contrasting eosinophils and eosinophil effector functions in human subjects versus mice. In particular, our review will provide a summation and an easy-to-use reference guide to important studies demonstrating that although differences exist, more often than not, their consequences are unknown and do not necessarily reflect inherent disparities in eosinophil function but instead species-specific variations. The conclusion from this overview is that despite nominal differences, the vast similarities between human and mouse eosinophils provide important insights as to their roles in health and disease and, in turn, demonstrate the unique utility of mouse-based studies with an expectation of valid extrapolation to the understanding and treatment of patients.

Human cord blood derived immature basophils show dual characteristics, expressing both basophil and eosinophil associated proteins

Basophils are blood cells of low abundance associated with allergy, inflammation and parasite infections. To study the transcriptome of mature circulating basophils cells were purified from buffy coats by density gradient centrifugations and two-step magnetic cell sorting. However, after extensive analysis the cells were found to be transcriptionally inactive and almost completely lack functional mRNA. In order to obtain transcriptionally active immature basophils for analysis of their transcriptome, umbilical cord blood cells were therefore cultured in the presence of interleukin (IL)-3 for 9 days and basophils were enriched by removing non-basophils using magnetic cell sorting. The majority of purified cells demonstrated typical metachromatic staining with Alcian blue dye (95%) and expression of surface markers FcεRI and CD203c, indicating a pure population of cells with basophil-like phenotype. mRNA was extracted from these cells and used to construct a cDNA library with approximately 600 000 independent clones. This library served as tool to determine the mRNA frequencies for a number of hematopoietic marker proteins. It was shown that these cells express basophil/mast cell-specific transcripts, i.e. β-tryptase, serglycin and FcεRI α-chain, to a relatively low degree. In contrast, the library contained a high number of several eosinophil-associated transcripts such as: major basic protein (MBP), charcot leyden crystal (CLC), eosinophil cationic protein (ECP), eosinophil derived neurotoxin (EDN) and eosinophil peroxidase (EPO). Out of these transcripts, MBP and EPO were the most frequently observed, representing 8% and 3.2% of the total mRNA pool, respectively. Moreover, in a proteome analysis of cultured basophils we identified MBP and EPO as the two most prominent protein bands, suggesting a good correlation between protein and mRNA analyses of these cells. The mixed phenotype observed for these cells strengthens the conclusion that eosinophils and basophils are closely linked during human hematopoietic development. The dual phenotype also indicates that other cytokines than IL-3 or cell surface interactions are needed to obtain the full basophil specific phenotype in vivo.

Cofactor-mediated restriction of GATA-1 chromatin occupancy coordinates lineage-specific gene expression

GATA-1 and its cofactor FOG-1 are required for the differentiation of erythrocytes and megakaryocytes. In contrast, mast cell development requires GATA-1 and the absence of FOG-1. Through genome-wide comparison of the chromatin occupancy of GATA-1 and a naturally occurring mutant that cannot bind FOG-1 (GATA-1(V205G)), we reveal that FOG-1 intricately regulates the chromatin occupancy of GATA-1. We identified GATA1-selective and GATA-1(V205G)-selective binding sites and show that GATA-1, in the absence of FOG-1, occupies GATA-1(V205G)-selective sites, but not GATA1-selective sites. By integrating ChIP-seq and gene expression data, we discovered that GATA-1(V205G) binds and activates mast cell-specific genes via GATA-1(V205G)-selective sites. We further show that exogenous expression of FOG-1 in mast cells leads to displacement of GATA-1 from mast cell-specific genes and causes their downregulation. Together these findings establish a mechanism of gene regulation whereby a non-DNA binding cofactor directly modulates the occupancy of a transcription factor to control lineage specification.

How can microarrays unlock asthma?

Asthma is a complex disease regulated by the interplay of a large number of underlying mechanisms which contribute to the overall pathology. Despite various breakthroughs identifying genes related to asthma, our understanding of the importance of the genetic background remains limited. Although current therapies for asthma are relatively effective, subpopulations of asthmatics do not respond to these regimens. By unlocking the role of these underlying mechanisms, a source of novel and more effective treatments may be identified. In the new age of high-throughput technologies, gene-expression microarrays provide a quick and effective method of identifying novel genes and pathways, which would be impossible to discover using an individual gene screening approach. In this review we follow the history of expression microarray technologies and describe their contributions to advancing our current knowledge and understanding of asthma pathology.

ETV6-PDGFRB and FIP1L1-PDGFRA stimulate human hematopoietic progenitor cell proliferation and differentiation into eosinophils: the role of nuclear factor-κB

BACKGROUND

ETV6-PDGFRB (also called TEL-PDGFRB) and FIP1L1-PDGFRA are receptor-tyrosine kinase fusion genes that cause chronic myeloid malignancies associated with hypereosinophilia. The aim of this work was to gain insight into the mechanisms whereby fusion genes affect human hematopoietic cells and in particular the eosinophil lineage.

DESIGN AND METHODS

We introduced ETV6-PDGFRB and FIP1L1-PDGFRA into human CD34(+) hematopoietic progenitor and stem cells isolated from umbilical cord blood.

RESULTS

Cells transduced with these oncogenes formed hematopoietic colonies even in the absence of cytokines. Both oncogenes also stimulated the proliferation of cells in liquid culture and their differentiation into eosinophils. This model thus recapitulated key features of the myeloid neoplasms induced by ETV6-PDGFRB and FIP1L1-PDGFRA. We next showed that both fusion genes activated the transcription factors STAT1, STAT3, STAT5 and nuclear factor-κB. Phosphatidylinositol-3 kinase inhibition blocked nuclear factor-κB activation in transduced progenitor cells and patients' cells. Nuclear factor-κB was also activated in the human FIP1L1-PDGFRA-positive leukemia cell line EOL1, the proliferation of which was blocked by bortezomib and the IκB kinase inhibitor BMS-345541. A mutant IκB that prevents nuclear translocation of nuclear factor-κB inhibited cell growth and the expression of eosinophil markers, such as the interleukin-5 receptor and eosinophil peroxidase, in progenitors transduced with ETV6-PDGFRB. In addition, several potential regulators of this process, including HES6, MYC and FOXO3 were identified using expression microarrays.

CONCLUSIONS

We show that human CD34(+) cells expressing PDGFR fusion oncogenes proliferate autonomously and differentiate towards the eosinophil lineage in a process that requires nuclear factor-κB. These results suggest new treatment possibilities for imatinib-resistant myeloid neoplasms associated with PDGFR mutations.

Deciphering the structure and function of FcεRI/mast cell axis in the regulation of allergy and anaphylaxis: a functional genomics paradigm

Allergy and anaphylaxis are inflammatory disorders caused by immune reactions mainly induced by immunoglobulin-E that signal through the high-affinity FcεRI receptor to release the inflammatory mediators from innate immune cells. The FcεRI/mast cell axis is potently involved in triggering various intracellular signaling molecules to induce calcium release from the internal stores, induction of transcription factors such as NF-kB, secretion of various cytokines as well as lipid mediators, and degranulation, resulting in the induction of allergy and anaphylaxis. In this review, we discuss various cellular and molecular mechanisms triggered through FcεRI/mast cell axis in allergy and anaphylaxis with a special emphasis on the functional genomics paradigm.

Glycomic analysis of human mast cells, eosinophils and basophils

In allergic diseases such as asthma, eosinophils, basophils and mast cells, through release of preformed and newly generated mediators, granule proteins and cytokines, are recognized as key effector cells. While their surface protein phenotypes, mediator release profiles, ontogeny, cell trafficking and genomes have been generally explored and compared, there has yet to be any thorough analysis and comparison of their glycomes. Such studies are critical to understand the contribution of carbohydrates to the induction and regulation of allergic inflammatory responses and are now possible using improved technologies for detecting and characterizing cell-derived glycans. We thus report here the application of high-sensitivity mass spectrometric-based glycomics methodologies to the analysis of N-linked glycans derived from isolated populations of human mast cells, eosinophils and basophils. The samples were subjected to matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) screening analyses and MALDI-TOF/TOF sequencing studies. Results reveal substantive quantities of terminal N-acetylglucosamine containing structures in both the eosinophil and the basophil samples, whereas mast cells display greater relative quantities of sialylated terminal epitopes. For the first time, we characterize the cell surface glycan structures of principal allergic effector cells, which by interaction with glycan-binding proteins (e.g. lectins) have the possibility to dictate cellular functions, and might thus have important implications for the pathogenesis of inflammatory and allergic diseases.

Human eosinophils produce and release a novel chemokine, CCL23, in vitro

BACKGROUND

CCL23 (MPIF1/CK-BETA-8) is a novel CC chemokine that plays important roles in the inhibition of myeloid progenitor cell development, the selective recruitment of resting T lymphocytes and monocytes, and the potentiation of VEGF-induced proliferation and migration of human endothelial cells. Since eosinophils participate in the pathogenesis of airway remodeling, we examined CCL23 production and release by human eosinophils in vitro.

METHODS

Using Ficoll and antibody-coated immunomagnetic beads, eosinophils and other blood cells were purified from peripheral blood samples obtained from normal subjects and mildly allergic patients. Eosinophils were cultured in the presence of 10 ng/ml granulocyte-macrophage colony-stimulating factor (GM-CSF), 10 ng/ml IL-5, 100 ng/ml IFN-γ, 100 ng/ml IFN-α, or immobilized secretory IgA (sIgA). Total mRNA was extracted after 6 h of culture, and mRNA expression was measured using a microarray and RT-PCR. The CCL23 concentrations in the supernatants and cell lysates after 24 and 48 h of culture were measured by ELISA.

RESULTS

CCL23 mRNAs (both CK-β8-1 and CK-β8) were constitutively expressed in fresh eosinophils, and their expression levels were higher than in other types of blood cells. CCL23 mRNAs were significantly increased by stimulation with GM-CSF and IL-5 and slightly by IFN-α and immobilized sIgA. Fresh eosinophils contained trace amounts of CCL23 protein. CCL23 was significantly released into the supernatant when the eosinophils were stimulated with GM-CSF or IL-5 but not with IFN-γ or immobilized sIgA.

CONCLUSION

Our data suggest that eosinophils produce and release CCL23 and may be involved in some in vivo physiological and pathological conditions.

Corneal and conjunctival fibroblasts are major sources of eosinophil-recruiting chemokines

BACKGROUND

Differential expression of chemokine genes were investigated in various types of ocular surface cells.

METHODS

Primary cultures of human corneal epithelial cells (n = 3), corneal fibroblasts (n = 2), conjunctival epithelial cells (n = 2) and conjunctival fibroblasts (n = 2) were established and incubated with or without interleukin (IL)-4 (30ng/ml) and tumor necrosis factor (TNF)-alpha(30ng/ml) for 24 hours. Gene transcription levels of 33 chemokines and production of 4 chemokines were analyzed.

RESULTS

After stimulation, chemokine expression increased for 18 of 33 coded chemokine gene transcripts. In stimulated conjunctival and corneal cells, CC chemokine genes increased in fibroblasts (expression of 6 out of 8 genes), while CXC chemokine genes increased in both epithelial cells (expression of 4 out of 9 genes in conjunctival epithelial cells and 7 out of 9 genes in corneal epithelial cells) and in fibroblasts (expression of 8 out of 9 genes in conjunctival and corneal fibroblasts). Except for MCP-1, gene transcription levels for most CC chemokines were inducible and, except for IP-10 and I-TAC, most CXC chemokines were constitutively expressed. Corneal epithelial cell and fibroblast production patterns for eotaxin-1, MCP-1 and IP-10 were comparable to the mRNA expression pattern.

CONCLUSIONS

Corneal and conjunctival fibroblasts exhibited marked increases in the expression of chemokines upon stimulation with TNF-alpha and IL-4, suggesting that fibroblasts may be one of the primary sources of chemokines in allergic conjunctival diseases. Therefore, regulation of chemokine production from these cells may be an effective strategy for treating such diseases.

Estimation of gene induction enables a relevance-based ranking of gene sets

In order to handle and interpret the vast amounts of data produced by microarray experiments, the analysis of sets of genes with a common biological functionality has been shown to be advantageous compared to single gene analyses. Some statistical methods have been proposed to analyse the differential gene expression of gene sets in microarray experiments. However, most of these methods either require threshhold values to be chosen for the analysis, or they need some reference set for the determination of significance. We present a method that estimates the number of differentially expressed genes in a gene set without requiring a threshold value for significance of genes. The method is self-contained (i.e., it does not require a reference set for comparison). In contrast to other methods which are focused on significance, our approach emphasizes the relevance of the regulation of gene sets. The presented method measures the degree of regulation of a gene set and is a useful tool to compare the induction of different gene sets and place the results of microarray experiments into the biological context. An R-package is available.

Physiological and pathophysiological functions of intestinal mast cells

The normal gastrointestinal (GI) mucosa is equipped with mast cells that account for 2-3% of lamina propria cells under normal conditions. Mast cells are generally associated with allergic disease, and indeed, food allergy that manifests in the GI tract is usually mast cell dependent. On the other hand, mast cells have a number of physiological functions in the GI tract, namely regulatory functions such as control of blood flow and coagulation, smooth muscle contraction and peristalsis, and secretion of acid, electrolytes, and mucus by epithelial cells. One of the most intriguing functions of intestinal mast cells is their role in host defense against microbes like bacteria, viruses, or parasites. Mast cells recognize microbes by antibody-dependent mechanisms and through pattern-recognition receptors. They direct the subsequent immune response by attracting both granulocytes and lymphocytes to the site of challenge via paracrine cytokine release. Moreover, mast cells initiate, by releasing proinflammatory mediators, innate defense mechanisms such as enhanced epithelial secretion, peristalsis, and alarm programs of the enteric nervous This initiation can occur in response to a primary contact to the microbe or other danger signals, but becomes much more effective if the triggering antigen reappears and antibodies of the IgE or IgG type have been generated in the meantime by the specific immune system. Thus, mast cells operate at the interface between innate and adaptive immune responses to enhance the defense against pathogens and, most likely, the commensal flora. In this respect, it is important to note that mast cells are directly involved in controlling the function of the intestinal barrier that turned out to be a crucial site for the development of infectious and immune-mediated diseases. Hence, intestinal mast cells perform regulatory functions to maintain tissue homeostasis, they are involved in host defense mechanisms against pathogens, and they can induce allergy once they are sensitized against foreign antigens. The broad spectrum of functions makes mast cells a fascinating target for future pharmacological or nutritional interventions.

Characterization of gene expression profiles for different types of mast cells pooled from mouse stomach subregions by an RNA amplification method

Background

Mast cells (MCs) play pivotal roles in allergy and innate immunity and consist of heterogenous subclasses. However, the molecular basis determining the different characteristics of these multiple MC subclasses remains unclear.

Results

To approach this, we developed a method of RNA extraction/amplification for intact in vivo MCs pooled from frozen tissue sections, which enabled us to obtain the global gene expression pattern of pooled MCs belonging to the same subclass. MCs were isolated from the submucosa (sMCs) and mucosa (mMCs) of mouse stomach sections, respectively, 15 cells were pooled, and their RNA was extracted, amplified and subjected to microarray analysis. Known marker genes specific for mMCs and sMCs showed expected expression trends, indicating accuracy of the analysis.

We identified 1,272 genes showing significantly different expression levels between sMCs and mMCs, and classified them into clusters on the basis of similarity of their expression profiles compared with bone marrow-derived MCs, which are the cultured MCs with so-called 'immature' properties. Among them, we found that several key genes such as Notch4 had sMC-biased expression and Ptgr1 had mMC-biased expression. Furthermore, there is a difference in the expression of several genes including extracellular matrix protein components, adhesion molecules, and cytoskeletal proteins between the two MC subclasses, which may reflect functional adaptation of each MC to the mucosal or submucosal environment in the stomach.

Conclusion

By using the method of RNA amplification from pooled intact MCs, we characterized the distinct gene expression profiles of sMCs and mMCs in the mouse stomach. Our findings offer insight into possible unidentified properties specific for each MC subclass.

Interleukin-3 does not affect the differentiation of mast cells derived from human bone marrow progenitors

Although IL-3 is commonly used for culture of human progenitor-derived mast cells together with Stem cell factor (SCF) and IL-6, the effect of IL-3 on human mast cell differentiation has not been well elucidated. Human bone marrow CD34+ progenitors were cultured for up to 12 weeks in the presence of rhSCF and rhIL-6 either with rhIL-3 (IL-3 (+)) or without rhIL-3 (IL-3 (−)) for the initial 1-week of culture. Total cell number increased at 2 weeks in IL-3 (+), as compared to IL-3 (−), but changes in the appearance of mast cells were delayed. When IL-3 was present for the initial 1-week culture, granules looked more mature with IL-3 than without IL-3. However, tryptase and chymase contents, and surface antigen expression (CD18, CD51, CD54, and CD117) were not altered by IL-3. Surface expression and mRNA level of FcεRIα and histamine release by crosslinking of FcεRIα did not differ from one preparation to the next. GeneChip analysis revealed that no significant differences were observed between IL-3 (+) and IL-3 (−) cells either when inactivated or activated by aggregation of FcεRIα. These findings indicate that initial incubation of human bone marrow CD34+ progenitors with IL-3 does not affect the differentiation of mast cells.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Costimulation and allergic responses: immune and bioinformatic analyses

Asthma is a complex polygenic disease, the prevalence of which has been on the rise for last few decades. Defining the underpinnings of allergic immune responses and the factors predisposing to asthma are fundamental investigative challenges. T cell costimulatory pathways play critical roles in the pathogenesis of asthma. In this review, we analyze the current state of the art of T cell costimulation in allergic airway inflammation. Also, we discuss both immune and bioinformatic approaches as potential strategies for analyzing multiple costimulatory pathways relevant to asthma.

The usefulness of post-genomics tools for characterization of the amine cross-talk in mammalian cells

Evidence is growing in favour of a relationship between cancer and chronic inflammation, and particularly of the role of a polyamine and histamine metabolic interplay involved in these physiopathological problems, which are indeed highly complex biological systems. Decodification of the complex inter- and intra-cellular signalling mechanisms that control these effects is not an easy task, which must be helped by systems biology technologies, including new tools for location and integration of database-stored information and predictive mathematical models, as well as functional genomics and other experimental molecular approaches necessary for hypothesis validation. We review the state of the art and present our latest efforts in this area, focused on the amine metabolism field.

Role of mast cells in allergic and non-allergic immune responses: comparison of human and murine data

The versatile role of mast cells in allergy, in innate immune responses and in the regulation of tissue homeostasis is well recognized. However, it is often not made clear that most mast-cell data derive solely from experiments in mice or rats, species that obviously never suffer from allergic and most other mast-cell-associated human diseases. Data on human mast cells are limited, and the mast-cell source and species from which findings derive are frequently not indicated in the titles and summaries of research publications. This Review summarizes recent data on human mast cells, discusses differences with murine mast cells, and describes new tools to study this increasingly meaningful cell type in humans.

Genome-wide gene expression profiling of human mast cells stimulated by IgE or FcepsilonRI-aggregation reveals a complex network of genes involved in inflammatory responses

Background

Mast cells are well established effectors of IgE-triggered allergic reactions and immune responses to parasitic infections. Recent studies indicate that mast cells may play roles in adaptive and innate immunity, suggesting an innovative view of the regulation of immune responses. Here, we profiled the transcriptome of human mast cells sensitized with IgE alone, or stimulated by FcεRI aggregation.

Results

Our data show that among 8,793 genes examined, 559 genes are differentially regulated in stimulated mast cells when compared with resting/unstimulated mast cells. The major functional categories of upregulated genes include cytokines, chemokines, and other genes involved in innate and adaptive immune-responses. We observed the increased expression of over 63 gene-transcripts following IgE-sensitization alone. Our data was validated using Real-Time-PCR; ELISA and western blot. We confirmed that IgE alone does not trigger mast cell-immediate responses, such as calcium signals, degranulation or protein-phosphorylation.

Conclusion

This report represents a substantial advance in our understanding of the genome wide effects triggered by "passive sensitization" or active stimulation of human mast cells, supporting mast cells' potential involvement in a wide range of inflammatory responses.

Generation and characterization of bone marrow-derived cultured canine mast cells

Disorders of mast cells, particularly mast cell tumors (MCTs), are common in dogs. There now is evidence that many of these disorders exhibit breed predilections, suggesting an underlying heritable component. In comparison to humans and mice, little is known regarding the biology of canine mast cells. To facilitate the study of mast cell biology in other species, bone marrow-derived cultured mast cells (BMCMCs) often are used because these represent a ready source of large numbers of cells. We have developed a protocol to successfully generate canine BMCMCs from purified CD34(+) cells. After 5-7 weeks of culture with recombinant canine stem cell factor (rcSCF), greater than 90% of the cell population consisted of mast cells as evidenced by staining with Wright's-Giemsa, as well as production of chymase, tryptase, IL-8 and MCP-1. These cells expressed cell surface markers typical of mast cells including Kit, Fc epsilonRI, CD44, CD45 and CD18/CD11b. The canine BMCMCs were dependent on rcSCF for survival and proliferation, and migrated in response to rcSCF gradients. Cross-linking of cell surface-bound IgE induced the release of histamine and TNFalpha. Histamine release could also be stimulated by ConA, compound 48/80, and calcium ionophore. In summary, canine BMCMCs possess phenotypic and functional properties similar to mast cells found in vivo. These cells represent a novel, valuable resource for investigating normal canine mast cell biology as well as for identifying factors that lead to mast cell dysregulation in the dog.

Alteration and acquisition of Siglecs during in vitro maturation of CD34+ progenitors into human mast cells

Using human mast cells (MC) derived by culture of CD34+ peripheral blood precursors, a comprehensive study was performed of expression of 11 known Siglecs. Analysis was initially performed at the mRNA level using gene arrays. Positive results were then validated at the protein level using indirect immunofluorescence and flow cytometry, and for some Siglecs, Western blot analysis was also used. Culture-derived MC expressed mRNA for CD22 (Siglec-2), CD33 (Siglec-3), Siglec-5, Siglec-6, Siglec-8 and Siglec-10. Flow cytometry confirmed surface expression of all these molecules except for CD22 and Siglec-10, where levels were low or undetectable. However, Western blotting was able to detect MC expression of CD22 and Siglec-10, suggesting that these proteins were mostly cytoplasmic. CD34+ precursor cells from peripheral blood constitutively expressed surface CD33, Siglec-5 and Siglec-10. As they matured into MC, their constitutive levels of CD33 changed little, Siglec-5 and Siglec-10 declined, and Siglec-6 and Siglec-8 appeared de novo, all in parallel with accumulation of histamine and other MC markers, such as surface expression of FcepsilonRIalpha, and CD51. Phenotypic analysis of LAD-2 MC yielded a similar pattern of Siglec expression except that CD22 expression was particularly prominent. Finally, immunohistochemistry confirmed expression of these same Siglecs by mature tryptase-positive MC in human lung tissues. These data demonstrate an extensive and previously unappreciated pattern of Siglec expression on human MC. Whether engagement and signaling through these inhibitory Siglecs can impact MC biology will require further investigation.

Increased expression of genes linked to FcepsilonRI Signaling and to cytokine and chemokine production in Lyn-deficient mast cells

Cross-linking the high-affinity IgE receptor, FcepsilonRI, on mast cells activates signaling pathways leading to the release of preformed inflammatory mediators and the production of cytokines and chemokines associated with allergic disorders. Bone marrow-derived mast cells (BMMCs) from Lyn-deficient (Lyn-/-) mice are hyperresponsive to FcepsilonRI cross-linking with multivalent Ag. Previous studies linked the hyperresponsive phenotype in part to increased Fyn kinase activity and reduced SHIP phosphatase activity in the Lyn-/- BMMCs in comparison with wild-type (WT) cells. In this study, we compared gene expression profiles between resting and Ag-activated WT and Lyn-/- BMMCs to identify other factors that may contribute to the hyperresponsiveness of the Lyn-/- cells. Among genes implicated in the positive regulation of FcepsilonRI signaling, mRNA for the tyrosine kinase, Fyn, and for several proteins contributing to calcium regulation are more up-regulated following Ag stimulation in Lyn-/- BMMCs than in WT BMMCs. Conversely, mRNA for the low-affinity IgG receptor (FcgammaRIIB), implicated in negative regulation of FcepsilonRI-mediated signaling, is more down-regulated in Ag-stimulated Lyn-/- BMMCs than in WT BMMCs. Genes coding for proinflammatory cytokines and chemokines (IL-4, IL-6, IL-13, CSF, CCL1, CCL3, CCL5, CCL7, CCL9, and MIP1beta) are all more highly expressed in Ag-stimulated Lyn-/- mast cells than in WT cells. These microarray data identify Lyn as a negative regulator in Ag-stimulated BMMCs of the expression of genes linked to FcepsilonRI signaling and also to the response pathways that lead to allergy and asthma.

Human lung mast cells adhere to human airway smooth muscle, in part, via tumor suppressor in lung cancer-1

Mast cells infiltrate the airway smooth muscle (ASM) of patients with asthma, an event which is likely to be a key factor in the development of this disease. Adhesion is a fundamental mechanism facilitating cellular cross-talk. We have examined whether human lung mast cells (HLMC) and ASM adhere, and have also examined the mechanism involved. Primary cultures of HLMC and confluent human ASM were cocultured for 30 min, then nonadherent HLMC were removed by centrifugation. HLMC adhered avidly to ASM monolayers (mean +/- SEM adhesion 43.2 +/- 1.2%, n = 41). Adhesion was increased to 58.8 +/- 2.7% by 1 mM Mn2+ (p = 0.015), and was reduced by EDTA and EGTA to 20.5 +/- 1.5% and 21.0 +/- 1.3%, respectively (p < 0.0001). Adhesion-blocking Abs for ICAM-1, VCAM-1, CD18, and the alpha4 and beta1 integrins had no effect on HLMC adhesion. HLMC expressed tumor suppressor in lung cancer-1 (TSLC-1) and blocking this reduced adhesion from 38.5 +/- 4.8% to 28.3 +/- 3.7% (p = 0.004, n = 7). ASM did not express TSLC-1, indicating that TSLC-1 acts as a heterophilic adhesion molecule. In summary, HLMC adhere avidly to ASM in part via TSLC-1 and in part via an as-yet-undefined Ca2+-dependent pathway. This supports the hypothesis that adhesion is important in the recruitment and retention of HLMC by the ASM in asthma, and for the functional interaction of these cells.

Role of structural cells of the cornea and conjunctiva in the pathogenesis of vernal keratoconjunctivitis

Vernal keratoconjunctivitis (VKC) is a severe type of allergic conjunctival disease characterized by the presence both of various corneal epithelial and stromal lesions as well as of conjunctival proliferative changes such as giant papillae of the upper tarsal conjunctiva and limbal lesions. These clinical findings as well as various pathophysiological characteristics of VKC are distinct from those of other types of ocular allergy and allergic diseases of other organs. The outer eye possesses specific allergological characteristics, one of which is communication between the cornea and conjunctiva through a thin layer of tear fluid. Fibroblasts of the cornea and the conjunctiva are activated by proinflammatory and T helper 2 (Th2) cell-derived cytokines. Corneal fibroblasts enhance ocular allergic reactions as a result of their activation-induced expression both of chemokines such as eotaxin and TARC as well as of adhesion molecules such as ICAM-1 and VCAM-1, all of which together promote the activation and infiltration of eosinophils and Th2 lymphocytes. In contrast, corneal epithelial cells suppress such reactions by physically separating corneal fibroblasts from bioactive substances in tear fluid. Exaggerated proliferation of and deposition of extracellular matrix by conjunctival fibroblasts likely exacerbate conjunctival inflammation. Restoration of an intact corneal epithelium and inhibition of the activities of corneal and conjunctival fibroblasts may provide a basis for the development of new treatments for severe ocular allergic diseases such as VKC.

Identification of tryptase- and chymase-related gene clusters in human mast cells using microarrays

Tryptase and chymase are the two major granular proteases present in human mast cell (MC)s. We used oligonucleotide microarray to measure the levels of approximately 22,000 transcripts in cord blood-derived MCs at 4 weeks, 8 weeks, 12 weeks and 18 weeks in culture. Tryptase (TPSB2) was expressed at the highest level among all transcripts and its expression level reached a plateau at 8 weeks. On the other hand, the expression level of chymase (CMAI) doubled every 4-6 weeks. A similar tendency was found at the protein levels with FACS analysis. After filtering the transcripts with MC-specificity, hierarchical clustering analysis identified 494 and 81 transcripts in the same clusters with tryptase and chymase, respectively. MC-specific genes, KIT and HDC were found in the tryptase cluster. In the chymase cluster, a critical suppressor for cell senescence, BMI1 and the several related genes were found, suggesting that chymase expression may be closely related to cell senescence/quiescence events.

Identification of basophils by a mAb directed against pro-major basic protein 1

BACKGROUND

Basophils possess characteristics of both mast cells and eosinophils, and all 3 cell types often are found together, particularly during allergic reactions. A mAb (J175-7D4) generated against the recombinant pro-form of human eosinophil granule major basic protein 1 (rproMBP1) appeared to stain only basophils in tissue specimens.

OBJECTIVE

We investigated J175-7D4 to characterize its specificity for basophils.

METHODS

Fluid-phase immunoprecipitation, Western blotting, and immunocytochemistry and immunohistochemistry were used to establish the specificity of J175-7D4.

RESULTS

First, J175-7D4 binds to various glycosylated and proteolytically processed forms of rproMBP1, but not to major basic protein. Second, cells transfected with the rproMBP1 gene and human placental tissue (known to express the pro-form of major basic protein 1 [proMBP1]) stain specifically with J175-7D4. In contrast, although mature eosinophils contain substantial major basic protein, they lack proMBP1 and do not stain. Neutrophils, lymphocytes, monocytes, and skin mast cells also are not stained. However, blood basophils are stained by J175-7D4, anti-IgE, Wright-Giemsa (metachromatically), and a previously characterized basophil-specific mAb, 2D7. Finally, formaldehyde-fixed, paraffin-embedded basophils are identically detected by J175-7D4 and 2D7, and J175-7D4 also recognizes putative basophils in formaldehyde-fixed, paraffin-embedded tissue specimens from inflammatory dermatoses, such as atopic dermatitis and delayed pressure urticaria.

CONCLUSION

The J175-7D4 mAb recognizes proMBP1 as a novel marker for human basophils. J175-7D4 should prove useful for characterizing basophil involvement in human health and disease.

Clues to asthma pathogenesis from microarray expression studies

Asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness (AHR), tissue remodeling, and airflow obstruction. The pathogenesis of asthma is only partly understood, and there is an urgent need for improved therapeutic strategies for this disease. Microarray technology has considerable promise as a tool for discovery of novel asthma therapeutic targets, although the field is still in its infancy. A number of studies have described expression profiles derived from human asthmatic lung tissue, mouse airway tissue, or from key cell types associated with asthma, but to date relatively few studies have exploited these findings to discover new pathways involved in the pathogenesis of asthma. Among the genes to have been identified by array studies and validated by further studies are monokine induced by interferon (IFN)-gamma, fatty acid binding proteins (FABP), and complement factor 5 (C5). Here we provide examples of microarray approaches to the discovery of new molecules associated with asthma. We anticipate that these types of analyses will provide considerable insight into asthma pathogenesis and will provide a wealth of new molecules for downstream analyses such as gene deficient mouse studies, or monoclonal antibody production.