Subsets of CD1c+ DCs: Dendritic Cell Versus Monocyte Lineage

Currently three bona fide dendritic cell (DC) types are distinguished in human blood. Herein we focus on type 2 DCs (DC2s) and compare the three defining markers CD1c, CD172, and CD301. When using CD1c to define DC2s, a CD14⁺ and a CD14⁻ subset can be detected. The CD14⁺ subset shares features with monocytes, and this includes substantially higher expression levels for CD64, CD115, CD163, and S100A8/9. We review the current knowledge of these CD1c⁺CD14⁺ cells as compared to the CD1c⁺CD14⁻ cells with respect to phenotype, function, transcriptomics, and ontogeny. Here, we discuss informative mutations, which suggest that two populations have different developmental requirements. In addition, we cover subsets of CD11c⁺CD8⁻ DC2s in the mouse, where CLEC12A⁺ESAM^low cells, as compared to the CLEC12A⁻ESAM^high subset, also express higher levels of monocyte-associated markers CD14, CD3, and CD115. Finally, we summarize, for both man and mouse, the data on lower antigen presentation and higher cytokine production in the monocyte-marker expressing DC2 subset, which demonstrate that the DC2 subsets are also functionally distinct.

Epigenetics in non-classical monocytes support their pro-inflammatory gene expression

Non-classical human monocytes are characterized by high-level expression of cytokines like TNF, but the mechanisms involved are elusive. We have identified miRNAs and CpG-methylation sites that are unique to non-classical monocytes, defined via CD14 and CD16 expression levels. For down-regulated miRNAs that are linked to up-regulated mRNAs the dominant gene ontology term was intracellular signal transduction. This included down-regulated miRNA-20a-5p and miRNA-106b-5p, which both are linked to increased mRNA for the TRIM8 signaling molecule. Methylation analysis revealed 16 hypo-methylated CpG sites upstream of 14 differentially increased mRNAs including 2 sites upstream of TRIM8. Consistent with a positive role in signal transduction, high TRIM8 levels went along with high basal TNF mRNA levels in non-classical monocytes. Since cytokine expression levels in monocytes strongly increase after stimulation with toll-like-receptor ligands, we have analyzed non-classical monocytes (defined via slan expression) after stimulation with lipopolysaccharide (LPS). LPS-stimulated cells continued to have low miRNA-20a and miRNA-106b and high TRIM8 mRNA levels and they showed a 10-fold increase in TNF mRNA. These data suggest that decreased miRNAs and CpG hypo-methylation is linked to enhanced expression of TRIM8 and that this can contribute to the increased TNF levels in non-classical human monocytes.

High degree of polyclonality hinders somatic mutation calling in lung brush samples of COPD cases and controls

Chronic obstructive pulmonary disease (COPD) is induced by cigarette smoking and characterized by inflammation of airway tissue. Since smokers with COPD have a higher risk of developing lung cancer than those without, we hypothesized that they carry more mutations in affected tissue. We called somatic mutations in airway brush samples from medium-coverage whole genome sequencing data from healthy never and ex-smokers (n = 8), as well as from ex-smokers with variable degrees of COPD (n = 4). Owing to the limited concordance of resulting calls between the applied tools we built a consensus, a strategy that was validated with high accuracy for cancer data. However, consensus calls showed little promise of representing true positives due to low mappability of corresponding sequence reads and high overlap with positions harbouring known genetic polymorphisms. A targeted re-sequencing approach suggested that only few mutations would survive stringent verification testing and that our data did not allow the inference of any difference in the mutational load of bronchial brush samples between former smoking COPD cases and controls. High polyclonality in airway brush samples renders medium-depth sequencing insufficient to provide the resolution to detect somatic mutations. Deep sequencing data of airway biopsies are needed to tackle the question.

Resistome analyses of sputum from COPD and healthy subjects reveals bacterial load-related prevalence of target genes

BACKGROUND

Antibiotic resistance is a major global threat. We hypothesised that the chronic obstructive pulmonary disease (COPD) airway is a reservoir of antimicrobial resistance genes (ARGs) that associate with microbiome-specific COPD subgroups.

OBJECTIVE

To determine the resistance gene profiles in respiratory samples from COPD patients and healthy volunteers.

METHODS

Quantitative PCR targeting 279 specific ARGs was used to profile the resistomes in sputum from subjects with COPD at stable, exacerbation and recovery visits (n=55; COPD-BEAT study), healthy controls with (n=7) or without (n=22) exposure to antibiotics in the preceding 12 months (EXCEED study) and in bronchial brush samples from COPD (n=8) and healthy controls (n=7) (EvA study).

RESULTS

ARG mean (SEM) prevalence was greater in stable COPD samples (35.2 (1.6)) than in healthy controls (27.6 (1.7); p=0.004) and correlated with total bacterial abundance (r²=0.23; p<0.001). Prevalence of ARG positive signals in individuals was not related to COPD symptoms, lung function or their changes at exacerbation. In the COPD subgroups designated High γProteobacteria and High Firmicutes, ARG prevalence was not different at stable state but significantly declined from stable through exacerbation to recovery in the former (p=0.011) without changes in total bacterial abundance. The ARG patterns were similar in COPD versus health, COPD microbiome-subgroups and between sputum and bronchoscopic samples independent of antibiotic exposure in the last 12 months.

CONCLUSIONS

ARGs are highly prevalent in sputum, broadly in proportion to bacterial abundance in both healthy and COPD subjects. Thus, COPD appears to be an ARG reservoir due to high levels of bacterial colonisation.

6-Sulfo LacNAc (Slan) as a Marker for Non-classical Monocytes

Monocytes are subdivided into three subsets, which have different phenotypic and functional characteristics and different roles in inflammation and malignancy. When in man CD14 and CD16 monoclonal antibodies are used to define these subsets, then the distinction of non-classical CD14low and intermediate CD14high monocytes requires setting a gate in what is a gradually changing level of CD14 expression. In the search for an additional marker to better dissect the two subsets we have explored the marker 6-sulfo LacNAc (slan). Slan is a carbohydrate residue originally described to be expressed on the cell surface of a type of dendritic cell in human blood. We elaborate herein that the features of slan+ cells are congruent with the features of CD16+ non-classical monocytes and that slan is a candidate marker for definition of non-classical monocytes. The use of this marker may help in studying the role of non-classical monocytes in health and in diagnosis and monitoring of disease.

Influence of lung CT changes in chronic obstructive pulmonary disease (COPD) on the human lung microbiome

BACKGROUND

Changes in microbial community composition in the lung of patients suffering from moderate to severe COPD have been well documented. However, knowledge about specific microbiome structures in the human lung associated with CT defined abnormalities is limited.

METHODS

Bacterial community composition derived from brush samples from lungs of 16 patients suffering from different CT defined subtypes of COPD and 9 healthy subjects was analyzed using a cultivation independent barcoding approach applying 454-pyrosequencing of 16S rRNA gene fragment amplicons.

RESULTS

We could show that bacterial community composition in patients with changes in CT (either airway or emphysema type changes, designated as severe subtypes) was different from community composition in lungs of patients without visible changes in CT as well as from healthy subjects (designated as mild COPD subtype and control group) (PC1, Padj = 0.002). Higher abundance of Prevotella in samples from patients with mild COPD subtype and from controls and of Streptococcus in the severe subtype cases mainly contributed to the separation of bacterial communities of subjects. No significant effects of treatment with inhaled glucocorticoids on bacterial community composition were detected within COPD cases with and without abnormalities in CT in PCoA. Co-occurrence analysis suggests the presence of networks of co-occurring bacteria. Four communities of positively correlated bacteria were revealed. The microbial communities can clearly be distinguished by their associations with the CT defined disease phenotype.

CONCLUSION

Our findings indicate that CT detectable structural changes in the lung of COPD patients, which we termed severe subtypes, are associated with alterations in bacterial communities, which may induce further changes in the interaction between microbes and host cells. This might result in a changed interplay with the host immune system.

Reprint of: MicroRNA profiling of human intermediate monocytes

Among the three human monocyte subsets, intermediate CD14++CD16+ monocytes have been characterized as particularly proinflammatory cells in experimental studies and as potential biomarkers of cardiovascular risk in clinical cohorts. To further substantiate the distinct role of intermediate monocytes within human monocyte heterogeneity, we assessed subset-specific expression of miRNAs as central epigenetic regulators of gene expression. We hypothesized that intermediate monocytes have a distinct miRNA profile compared to classical and non-classical monocytes. By using small RNA-seq we analyzed 662 miRNAs in the three monocyte subsets. We identified 38 miRNAs that are differentially expressed in intermediate monocytes compared to both classical and non-classical monocytes with a p value of <10^-10, of which two miRNAs - miR-6087 (upregulated) and miR-150-5p (downregulated) - differed in their expression more than ten-fold. Pathway analysis of the 38 differentially expressed miRNAs linked intermediate monocytes to distinct biological processes such as gene regulation, cell differentiation, toll-like receptor signaling as well as antigen processing and presentation. Moreover, differentially expressed miRNAs were connected to those genes that we previously identified as markers of intermediate monocytes. In aggregation, we provide first genome-wide miRNA data in the context of monocyte heterogeneity, which substantiate the concept of monocyte trichotomy in human immunity. The identification of miRNAs that are specific for intermediate monocytes may allow to develop strategies, which particularly target this cell population while sparing the other two subsets.

MicroRNA profiling of human intermediate monocytes

Among the three human monocyte subsets, intermediate CD14++CD16+ monocytes have been characterized as particularly proinflammatory cells in experimental studies and as potential biomarkers of cardiovascular risk in clinical cohorts. To further substantiate the distinct role of intermediate monocytes within human monocyte heterogeneity, we assessed subset-specific expression of miRNAs as central epigenetic regulators of gene expression. We hypothesized that intermediate monocytes have a distinct miRNA profile compared to classical and non-classical monocytes. By using small RNA-seq we analyzed 662 miRNAs in the three monocyte subsets. We identified 38 miRNAs that are differentially expressed in intermediate monocytes compared to both classical and non-classical monocytes with a p value of <10^-10, of which two miRNAs - miR-6087 (upregulated) and miR-150-5p (downregulated) - differed in their expression more than ten-fold. Pathway analysis of the 38 differentially expressed miRNAs linked intermediate monocytes to distinct biological processes such as gene regulation, cell differentiation, toll-like receptor signaling as well as antigen processing and presentation. Moreover, differentially expressed miRNAs were connected to those genes that we previously identified as markers of intermediate monocytes. In aggregation, we provide first genome-wide miRNA data in the context of monocyte heterogeneity, which substantiate the concept of monocyte trichotomy in human immunity. The identification of miRNAs that are specific for intermediate monocytes may allow to develop strategies, which particularly target this cell population while sparing the other two subsets.

Emphysema- and airway-dominant COPD phenotypes defined by standardised quantitative computed tomography

EvA (Emphysema versus Airway disease) is a multicentre project to study mechanisms and identify biomarkers of emphysema and airway disease in chronic obstructive pulmonary disease (COPD). The objective of this study was to delineate objectively imaging-based emphysema-dominant and airway disease-dominant phenotypes using quantitative computed tomography (QCT) indices, standardised with a novel phantom-based approach.441 subjects with COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages 1-3) were assessed in terms of clinical and physiological measurements, laboratory testing and standardised QCT indices of emphysema and airway wall geometry.QCT indices were influenced by scanner non-conformity, but standardisation significantly reduced variability (p<0.001) and led to more robust phenotypes. Four imaging-derived phenotypes were identified, reflecting "emphysema-dominant", "airway disease-dominant", "mixed" disease and "mild" disease. The emphysema-dominant group had significantly higher lung volumes, lower gas transfer coefficient, lower oxygen (PO2 ) and carbon dioxide (PCO2 ) tensions, higher haemoglobin and higher blood leukocyte numbers than the airway disease-dominant group.The utility of QCT for phenotyping in the setting of an international multicentre study is improved by standardisation. QCT indices of emphysema and airway disease can delineate within a population of patients with COPD, phenotypic groups that have typical clinical features known to be associated with emphysema-dominant and airway-dominant disease.

Blood Monocytes and Their Subsets: Established Features and Open Questions

In contrast to the past reliance on morphology, the identification and enumeration of blood monocytes are nowadays done with monoclonal antibodies and flow cytometry and this allows for subdivision into classical, intermediate, and non-classical monocytes. Using specific cell surface markers, dendritic cells in blood can be segregated from these monocytes. While in the past, changes in monocyte numbers as determined in standard hematology counters have not had any relevant clinical impact, the subset analysis now has uncovered informative changes that may be used in management of disease.

Comparison of two different strategies for human monocyte subsets gating within the large-scale prospective CARE FOR HOMe Study

Monocytes are heterogeneous cells consisting of (at least) three subsets: classical, intermediate, and nonclassical monocytes. Correct enumeration of cell counts necessitates well-defined gating strategies, which are essentially based upon CD14 and CD16 expression. For the delineation of intermediate from nonclassical monocytes, a "rectangular gating (RG) strategy" and a "trapezoid gating (TG) strategy" have been proposed. We compared the two gating strategies in a well-defined clinical cohort of patients with chronic kidney disease (CKD). Within the ongoing CARE FOR HOMe study, monocyte subsets were reanalyzed in 416 CKD patients, who were followed 3.6 ± 1.6 years for the occurrence of a cardiovascular event. Gating was performed by either RG or TG. We analyzed the expression of surface markers, and compared the predictive role of cell counts of monocyte subsets, as defined by RG and TG, respectively. With both gating strategies, higher intermediate monocyte counts predicted the cardiovascular endpoint in Kaplan-Meier analyses (P < 0.001 with RG; P < 0.001 with TG). After correction for confounders, intermediate monocyte counts remained independent predictors in Cox-Regression analyses (HR = 1.013 [95% CI: 1.006-1.020; P < 0.001] with RG; HR = 1.015 [95% CI: 1.006-1.024; P = 0.001] with TG). NRI was 3.9% when reclassifying patients from quartiles of intermediate monocyte counts with RG strategy toward quartiles of intermediate monocytes counts with TG strategy. In expression analysis, those monocytes which are defined as intermediate monocytes by the RG strategy and as nonclassical monocytes by the TG strategy share characteristics of both subsets. In conclusion, intermediate monocytes were independent predictors of cardiovascular outcome irrespective of the applied gating strategy. Future studies should aim to identify markers that allow for an unequivocal definition of intermediate monocytes, which may further improve their power to predict cardiovascular events.

Monocyte subsets in man and other species

Monocytes are white blood cells that belong to the mononuclear phagocyte system. They derive from precursors in bone marrow, from there they go into blood, where they have a half-life of 1-2 days, and then they migrate into the various tissues. Monocyte subsets were discovered by means of flow cytometry in human blood some 20 years ago and their phenotype and function has been characterized in detail in health and disease. The subset classification as classical, intermediate and non-classical monocytes appears to apply to other species as well, as reviewed in here by comparing data on human monocytes with the respective cells in the mouse, the rat, the pig, the cow and the horse. The data show that the subsets are homologous between the species but there are important differences in subset-specific gene expression such that findings in a given species cannot be directly translated to man.

Toward a refined definition of monocyte subsets

In a nomenclature proposal published in 2010 monocytes were subdivided into classical and non-classical cells and in addition an intermediate monocyte subset was proposed. Over the last couple of years many studies have analyzed these intermediate cells, their characteristics have been described, and their expansion has been documented in many clinical settings. While these cells appear to be in transition from classical to non-classical monocytes and hence may not form a distinct cell population in a strict sense, their separate analysis and enumeration is warranted in health and disease.

Transcript profiling of CD16-positive monocytes reveals a unique molecular fingerprint

CD16-positive (CD14(++) CD16(+) and CD14(+) CD16(++) ) monocytes have unique features with respect to phenotype and function. We have used transcriptional profiling for comparison of CD16-positive monocytes and classical monocytes. We show herein that 187 genes are greater than fivefold differentially expressed, including 90 genes relevant to immune response and inflammation. Hierarchical clustering of data for monocyte subsets and CD1c(+) myeloid blood dendritic cells (DCs) demonstrate that CD16-positive cells are more closely related to classical monocytes than to DCs. Reverse transcriptase polymerase chain reaction for ten genes with the strongest differential expression confirmed the pattern including a lower messenger RNA level for CD14, CD163, and versican in CD16-positive monocytes. The pattern was similar for CD16-positive monocytes at rest and after exercise mobilization from the marginal pool. By contrast, alveolar macrophages, small sputum macrophages, breast milk macrophages, and synovial macrophages all showed a different pattern. When monocyte-derived macrophages (MDMs) were generated from CD16-positive monocytes by culture with macrophage colony-stimulating factor in vitro, then the MDMs maintained properties of their progeny with lower expression of CD14, CD163, and versican compared with CD14(++) CD16(-) MDMs. Furthermore, CD16-positive MDMs showed a higher phagocytosis for opsonized Escherichia coli. The data demonstrate that CD16-positive monocytes form a distinct type of cell, which gives rise to a distinct macrophage phenotype.

The EvA study: aims and strategy

The EvA study is a European Union-funded project under the Seventh Framework Programme (FP7), which aims at defining new markers for chronic obstructive pulmonary disease (COPD) and its subtypes. The acronym is derived from emphysema versus airway disease, indicating that the project targets these two main phenotypes of the disease. The EvA study is based on the concept that emphysema and airway disease are governed by different pathophysiological processes, are driven by different genes and have differential gene expression in the lung. To define these genes, patients and non-COPD controls are recruited for clinical examination, lung function analysis and computed tomography (CT) of the lung. CT scans are used to define the phenotypes based on lung density and airway wall thickness. This is followed by bronchoscopy in order to obtain samples from the airways and the alveoli. These tissue samples, along with blood samples, are then subjected to genome-wide expression and association analysis and markers linked to the phenotypes are identified. The population of the EvA study is different from other COPD study populations, since patients with current oral glucocorticoids, antibiotics and exacerbations or current smokers are excluded, such that the signals detected in the molecular analysis are due to the distinct inflammatory process of emphysema and airway disease in COPD.

Chemokine expression by small sputum macrophages in COPD

Small sputum macrophages represent highly active cells that increase in the airways of patients with inflammatory diseases such as chronic obstructive pulmonary disease (COPD). It has been reported often that levels of cytokines, chemokines and pro-teases are increased in sputum supernatants of these patients. In COPD, the small sputum macrophages may contribute to these supernatant proteins and recruit additional cells via specific chemokine expression patterns. We therefore investigated the expression profile of chemokines in sputum macrophages obtained from COPD patients in comparison to cells from healthy donors and cells isolated after inhalation of lipopolysaccharide (LPS). We used the minimally invasive procedure of sputum induction and have purified macrophages with the RosetteSep technology. Using macrophage purification and flow cytometry we show that in COPD small sputum macrophages account for 85.9% ± 8.3% compared with 12.9% ± 7.1% of total macrophages in control donors. When looking at chemokine expression we found, for the small macrophages in COPD, increased transcript and protein levels for CCL2, CCL7, CCL13 and CCL22 with a more than 100-fold increase for CCL13 mRNA (P < 0.001). Looking at active smokers without COPD, there is a substantial increase of small macrophages to 60% ± 15% and, here, chemokine expression is increased as well. In a model of airway inflammation healthy volunteers inhaled 20 μg of lipopolysaccharide (LPS), which resulted in an increase of small sputum macrophages from 18% ± 19% to 64% ± 25%. The pattern of chemokine expression was, however, different with an upregulation for CCL2 and CCL7, while CCL13 was downregulated three-fold in the LPS-induced small macrophages. These data demonstrate that sputum macrophages in COPD show induction of a specific set of CCL chemokines, which is distinct from what can be induced by LPS.

Preparations of intravenous immunoglobulins diminish the number and proinflammatory response of CD14+CD16++ monocytes in common variable immunodeficiency (CVID) patients

We have studied the effect of intravenous immunoglobulins (IVIG) on monocyte subpopulations and cytokine production in patients with CVID. The absolute number of CD14(+)CD16(++) monocytes decreased on average 2.5-fold 4h after IVIG and after 20h returned to the baseline. The cytokine level in the supernatants of peripheral blood mononuclear cells (PBMC) after ex vivo LPS stimulation demonstrated the >2-fold decrease in TNF production 4h after IVIG. The TNF expression, which is higher in the CD14(+)CD16(++) monocytes, was decreased in these cells by IVIG in 4/7 CVID cases. In vitro exposure of the healthy individuals' monocytes to the IVIG preparation resulted in reduced TNF production, which was overcome by blockade of the FcγRIIB in the CD14(+)CD16(++) CD32B(high) monocytes. Our data suggest that reduction in the number of CD14(+)CD16(++) monocytes and the blockade of their cytokine production via triggering CD32B can contribute to the anti-inflammatory action of IVIG.

Standardized single-platform assay for human monocyte subpopulations: Lower CD14+CD16++ monocytes in females

We present a novel single-platform assay for determination of the absolute number of human blood monocyte subpopulations, i.e., the CD14(++)CD16(-) and the CD14(+)CD16(++) monocytes. A four-color combination of antibodies to CD14, CD16, CD45, and HLA-DR reduces the spill-over of natural killer cells and of granulocytes into the CD14(+)CD16(++) monocyte gate. For these CD14(+)CD16(++) monocytes, the intra-assay coefficient of variation (CV) was 4.1% and the inter-assay CV was 8.5%. Looking at a cohort of 40 donors aged 18-60 years, we found no age dependence. There was however an effect of gender in that females had lower CD14(+)CD16(++) monocytes (45.4 +/- 13.5 cells/microl) compared with males (59.1 +/- 20.3 cells/microl) (P < 0.02). Using this novel approach, we can confirm that exercise will lead to more than three-fold increase of the CD14(+)CD16(++) monocytes. Also, we show that therapy with low doses of glucocorticoids will deplete these cells. This robust single-platform assay may be a useful tool for monitoring the absolute number of monocyte subpopulations in health and disease.

Monocyte-derived macrophages matured under prolonged hypoxia transcriptionally up-regulate HIF-1α mRNA

This study tested the hypothesis that prolonged severe hypoxia during monocyte to macrophage differentiation results in macrophages with a pattern of gene expression and phenotype distinct from those maturing in normal oxygen levels. Macrophages accumulate in hypoxic and anoxic areas within pathological sites such as tumours, wounds, and arthritic joints, and have been proposed as vehicles for gene therapy delivery to such tissues. Several non-pathological tissues are also hypoxic. We therefore argue that differentiation from monocyte to macrophage in hypoxic conditions is a common occurrence. However, the effect of long term severe hypoxia on monocyte to macrophage differentiation has not been studied. Here, using primary human peripheral blood monocytes, we show that maturation for 5 days in 0.2% oxygen results in decreased phagocytosis, and decreased CD40 and CD206 expression. Chronic hypoxia induced much higher mRNA levels of the pro-angiogenic cytokine, VEGF, in adherence-purified macrophages (27-fold), CD14-magnetic bead purified monocytes (90-fold), and PBMC (104-fold) compared to acute (24h) hypoxia (11, 17 and 9-fold, respectively). This suggests that macrophages may play an even greater role in angiogenesis than previously appreciated. Furthermore, chronic hypoxia resulted in up-regulation of HIF-1α mRNA, in all monocyte-derived macrophage types studied. Actinomycin D experiments indicate that the increases in HIF-1α mRNA were not due to increased mRNA stability. To our knowledge this is the first study demonstrating up-regulation of HIF-1α mRNA by hypoxia in macrophages. Taken together, the data support the hypothesis that hypoxia affects monocyte to macrophage maturation, resulting in a distinct gene expression pattern and phenotype.

Ultrafine carbon particles down-regulate CYP1B1 expression in human monocytes

BACKGROUND

Cytochrome P450 monoxygenases play an important role in the defence against inhaled toxic compounds and in metabolizing a wide range of xenobiotics and environmental contaminants. In ambient aerosol the ultrafine particle fraction which penetrates deeply into the lungs is considered to be a major factor for adverse health effects. The cells mainly affected by inhaled particles are lung epithelial cells and cells of the monocyte/macrophage lineage.

RESULTS

In this study we have analyzed the effect of a mixture of fine TiO2 and ultrafine carbon black Printex 90 particles (P90) on the expression of cytochrome P450 1B1 (CYP1B1) in human monocytes, macrophages, bronchial epithelial cells and epithelial cell lines. CYP1B1 expression is strongly down-regulated by P90 in monocytes with a maximum after P90 treatment for 3 h while fine and ultrafine TiO2 had no effect. CYP1B1 was down-regulated up to 130-fold and in addition CYP1A1 mRNA was decreased 13-fold. In vitro generated monocyte-derived macrophages (MDM), epithelial cell lines, and primary bronchial epithelial cells also showed reduced CYP1B1 mRNA levels. Benzo[a]pyrene (BaP) is inducing CYB1B1 but ultrafine P90 can still down-regulate gene expression at 0.1 muM of BaP. The P90-induced reduction of CYP1B1 was also demonstrated at the protein level using Western blot analysis.

CONCLUSION

These data suggest that the P90-induced reduction of CYP gene expression may interfere with the activation and/or detoxification capabilities of inhaled toxic compounds.

Tolerance induced via TLR2 and TLR4 in human dendritic cells: role of IRAK-1

Background

While dendritic cells (DCs) can induce tolerance in T cells, little is known about tolerance induction in DCs themselves. We have analysed tolerance induced in human in-vitro generated DCs by repeated stimulation with ligands for TLR4 and TLR2.

Results

DCs stimulated with the TLR4 ligand LPS did show a rapid and pronounced expression of TNF mRNA and protein. When DCs were pre-cultured for 2 days with 5 ng LPS/ml then the subsequent response to stimulation with a high dose of LPS (500 ng/ml) was strongly reduced for both TNF mRNA and protein. At the promoter level there was a reduced transactivation by the -1173 bp TNF promoter and by a construct with a tetrameric NF-κB motif. Within the signalling cascade leading to NF-κB activation we found an ablation of the IRAK-1 adaptor protein in LPS-tolerant DCs. Pre-culture of DCs with the TLR2 ligand Pam3Cys also led to tolerance with respect to TNF gene expression and IRAK-1 protein was ablated in such tolerant cells as well, while IRAK-4 protein levels were unchanged.

Conclusion

These data show that TLR-ligands can render DCs tolerant with respect to TNF gene expression by a mechanism that likely involves blockade of signal transduction at the level of IRAK-1.

Monitoring of glucocorticoid therapy by assessment of CD14(+)CD16(+) monocytes: a case report

Bronchiolitis obliterans with organizing pneumonia (BOOP) is a disease affecting small airways and alveoli. It is characterized by interstitial inflammation rich in foamy macrophages and by fibroblastic connective tissue expanding into the airway and alveolar lumen. We report herein on a 54-year-old male BOOP patient who was treated with glucocorticoids (GCs) and who over a 5-year period had three relapses. At diagnosis the patient showed elevated CD14(+)CD16(+) monocyte numbers (85 cells/microl) and increased serum C-reactive protein (CRP) levels (29.4 mg/l). With GC therapy both parameters decreased within a few days. Diagnosis of relapse was preceded by a rise in CD14(+)CD16(+) monocyte numbers and in CRP levels which again responded to GC treatment. We conclude that determination of CD14(+)CD16(+) monocytes is a useful marker for monitoring of BOOP diagnosis and GC therapy.

Role of STAT3 in glucocorticoid-induced expression of the human IL-10 gene

In the present report we have determined the molecular mechanisms, which govern the expression of the human IL-10 gene when induced by the glucocorticoid Methyl-Prednisolone (MP). Treatment of cells with MP at 10(-6) M will readily induce IL-10 in CD19+ primary B cells and in a human B cell line. Analysis of the IL-10 promoter showed a robust 18-fold induction and demonstrated that a potential GRE motif was not required, while mutation of the -120 STAT-motif strongly reduced MP-induced trans-activation. A strong induction was also seen with a trimeric STAT-motif and over-expression of dominant-negative STAT3 could block MP induction of IL-10 mRNA. Finally, MP treatment induced binding of STAT3 to the promoter as shown by gelshift, supershift and by chromatin-immunoprecipitation. These data show that glucocorticoid-induced expression of the IL-10 gene is mediated by the transcription factor STAT3.

Expression of M-Ficolin in human monocytes and macrophages

M-Ficolin is a member of the ficolin family of proteins, which is expressed by monocytes. We have determined the expression of this gene in various populations of this lineage in man and found lower levels of M-Ficolin mRNA in the more mature CD14(+)CD16(+) monocytes as compared to the classical CD14(++) monocytes. Monocyte-derived macrophages generated by in vitro culture for 5 days strongly reduced M-Ficolin mRNA and protein. Mature tissue macrophages from the lung and from breast milk also showed a very low level of M-Ficolin transcripts. When cells of the monocytic cell line Mono Mac 6 cell were treated with TLR2 and TLR4 ligands for 24 h then there was an average of 6- and 9-fold induction of the M-Ficolin mRNA, respectively. After 72 h induction was in average 30- and 80-fold for TLR2 and TLR4 stimulation, respectively. Treatment of monocyte-derived macrophages for 3 days with TLR4 ligand gave an average 4-fold induction and alveolar macrophages treated with TLR4 ligand showed a 12-fold induction. These data show that M-Ficolin expression is silenced in macrophages but can be re-activated after prolonged activation via TLRs.

Elevated CD16 expression by monocytes from patients with tumor necrosis factor receptor-associated periodic syndrome

OBJECTIVE

Tumor necrosis factor receptor-associated periodic syndrome (TRAPS) is an inherited autosomal-dominant autoinflammatory condition caused by mutations in the ectodomain of the 55-kd tumor necrosis factor (TNF) receptor superfamily 1A. Proinflammatory blood monocytes with the phenotype CD14+,CD16+,HLA-DR++ are a major source of TNF, and the number of such monocytes is increased during infection and inflammation. The aim of this study was to investigate whether the expression of circulating CD16+ monocytes is affected in patients with TRAPS.

METHODS

Peripheral blood obtained from patients with TRAPS and healthy control subjects was stained with monoclonal antibodies to detect CD14++,CD16- monocytes and CD14+,CD16+ monocytes, using flow cytometry. Lipopolysaccharide-induced TNF production was measured by intracellular cytokine staining. Activation-induced shedding of CD16 was investigated by treating blood samples with phorbol myristate acetate.

RESULTS

The level of CD16 expression by CD14+,CD16+ monocytes, but not their absolute number, was significantly elevated in patients with TRAPS, even though the patients were not experiencing clinically overt episodes of autoinflammation at the time of sampling. These findings are similar to those for the C-reactive protein levels and erythrocyte sedimentation rates in the same patients. The enhanced level of CD16 expression by monocytes from patients with TRAPS was not attributable to a defect in activation-induced shedding of CD16. The CD14+,CD16+ monocytes were the predominant source of TNF in both patients and healthy control subjects.

CONCLUSION

The level of CD16 expression by monocytes was elevated in patients with TRAPS, as a feature of the underlying constitutive inflammation status.

IL-10 induces IL-10 in primary human monocyte-derived macrophages via the transcription factor Stat3

IL-10 is an important immunosuppressive cytokine that can down-regulate expression of other cytokines and has been shown to down-regulate itself. We show, in this study, that treatment of human monocyte-derived macrophages with IL-10 induces IL-10 mRNA in a dose- and time-dependent manner with an optimum induction at 100 ng/ml and at 6 h, whereas IL-10-induced IL-10 protein can be detected at 18 h. In the same cells, IL-10 can partially suppress IL-10 mRNA induced by LPS, but only down to the level of IL-10-induced IL-10. An adenoviral luciferase reporter construct driven by the -195 IL-10 promoter, which contains a Stat motif, was readily induced by both IL-10 and LPS. Mutation of this Stat motif ablated IL-10 activation of this promoter, but not the LPS activation. Finally, we show that overexpression of a dominant-negative Stat3 protein will prevent IL-10 induction, but not LPS induction, of IL-10 mRNA. These data show that IL-10 induces IL-10 in monocyte-derived macrophages in an autocrine manner via activation of the transcription factor Stat3.

The CD14+ CD16+ blood monocytes: their role in infection and inflammation

Blood monocyte subpopulations have been defined in man initially, and the two major types of monocytes are the CD14++ CD16- and the CD14+ CD16+ monocytes. These cells have been shown to exhibit distinct phenotype and function, and the CD14+ CD16+ were labeled proinflammatory based on higher expression of proinflammatory cytokines and higher potency in antigen presentation. The current review describes these properties, including the relationship to dendritic cells, and summarizes the host of publications about CD14+ CD16+ monocytes in inflammation and infectious disease in man, all of which suggest a crucial role of these cells in the disease processes. The review also covers the more recent description of homologues of these cells in other model species, which is expected to better define the role of monocyte subsets in disease.

A deletion defining a common Asian lineage of Mycobacterium tuberculosis associates with immune subversion

Six major lineages of Mycobacterium tuberculosis appear preferentially transmitted amongst distinct ethnic groups. We identified a deletion affecting Rv1519 in CH, a strain isolated from a large outbreak in Leicester U.K., that coincidentally defines the East African-Indian lineage matching a major ethnic group in this city. In broth media, CH grew less rapidly and was less acidic and H2O2-tolerant than reference sequenced strains (CDC1551 and H37Rv). Nevertheless, CH was not impaired in its ability to grow in human monocyte-derived macrophages. When compared with CDC1551 and H37Rv, CH induced less protective IL-12p40 and more antiinflammatory IL-10 and IL-6 gene transcription and secretion from monocyte-derived macrophages. It thus appears that CH compensates microbiological attenuation by skewing the innate response toward phagocyte deactivation. Complementation of Rv1519, but none of nine additional genes absent from CH compared with the type strain, H37Rv, reversed the capacity of CH to elicit antiinflammatory IL-10 production by macrophages. The Rv1519 polymorphism in M. tuberculosis confers an immune subverting phenotype that contributes to the persistence and outbreak potential of this lineage.

Inhalative vaccination with pneumococcal polysaccharide in patients with chronic obstructive pulmonary disease

In order to determine the feasibility of inhalative vaccination with polysaccharide antigen in patients with chronic obstructive pulmonary disease (COPD), we used controlled inhalation of a defined dose of Pneumovax in a randomized 3-arm study. The vaccine was either deposited in the alveoli (alveolar vaccination) or in the large airways (bronchial vaccination) and these were compared to standard intramuscular vaccination. Adverse effects were minor and never exceeded WHO grade 2. There was frequent cough, headache and shivering in the bronchial vaccination group, frequent fatigue only in the alveolar vaccination group and no frequent adverse effects in the intramuscular vaccination group. Specific serum IgG antibody was measured before and at 4 and 12 weeks after vaccination. At 12 weeks there was a greater than twofold rise in 7 out of 10 individuals in every vaccination group. Mean antibody levels of responders at 12 weeks were 278 mg/l for alveolar vaccination, 238 mg/l for bronchial vaccination and 737 mg/l for standard intramuscular vaccination. The data show that polysaccharide vaccine can be safely administered by controlled inhalation in COPD patients and that it can induce a rapid serum antibody response.

Vaccination with polysaccharide-conjugate-vaccines in adult patients with specific antibody deficiency

We report on a cohort of seven adult patients with specific antibody deficiency, defined by failure to respond to 23-valent Streptococcus pneumoniae vaccine while being able to respond to tetanus toxoid. Antibodies to Hemophilus influenzae (HiB) polysaccharides either pre-existed or were readily induced by a single vaccination with the HiB-tetanus toxoid conjugate. By contrast a single vaccination with the S. pneumoniae-diphtheria conjugate failed to induce a response to any of the seven serotypes in any of the seven patients. After a second vaccination in six patients, two patients continued to show no response but four showed a 3- to 45-fold response with development of >1 microg/ml of IgG to 2-4 of the serotypes, respectively. The data show that conjugate vaccines can enforce a response in adult patients with selective antibody deficiency but, dependent on the type of polysaccharide-conjugate, repeated immunisation and monitoring of the response is required.

Inhalative vaccination with pneumococcal polysaccharide in healthy volunteers

In order to determine the feasibility of inhalative vaccination with polysaccharide antigen, we used controlled inhalation of a defined dose of Pneumovax in a randomized 3-arm study. The vaccine was either deposited in the alveoli (alveolar vaccination) or in the large airways (bronchial vaccination) and this was compared to standard intra-muscular vaccination. Adverse effects were minor and never exceeded WHO grade 2. There was frequent cough in the inhalative groups and frequent local pain at the injection site in the intra-muscular group. Specific serum IgG antibody measured before, and 4 and 12 weeks after, vaccination showed a greater than 2-fold rise in 4 out of 10 individuals after alveolar vaccination and in 6 out of 10 individuals after bronchial vaccination as compared to 10 out of 10 in the intra-muscular vaccination group. Average antibody levels of responders at 12 weeks were 350 microg/ml for alveolar vaccination, 200 microg/ml for bronchial vaccination and 1010 microg/ml for standard intra-muscular vaccination. Analysis of antibodies for 9 specific serotypes showed a more than 3-fold rise to 7-9 of the serotypes in the intra-muscular group. In both the bronchial and the alveolar group, all subjects responded but this was restricted to 2-4 of the 9 serotypes. The data show that polysaccharide vaccine can be safely administered by controlled inhalation and that it can induce good, albeit lower, serum antibody responses.

Superior T cell activation by ESAT-6 as compared with the ESAT-6–CFP-10 complex

Using intracellular cytokine staining we show herein that T cells will respond to short-term (6 h) activation with phorbol ester plus ionomycin by production of tumor necrosis factor (TNF), IFN-gamma or both. Here CD4 T cells preferentially produce TNF and CD8 cells IFN-gamma. The same pattern is seen when T cells are activated with the Mycobacterium tuberculosis protein early secretory antigenic target-6 (ESAT-6). Responses with >0.02% IFN-gamma+ CD3 cells were seen in 8 of 10 patients diagnosed with tuberculosis and in 12 of 14 healthy individuals selected for likely exposure to M. tuberculosis. T cell responses to the 1:1 complex of ESAT-6 and culture filtrate protein-10 (CFP-10) were inferior to ESAT-6 alone, and only reached the level of T cell response achieved with CFP-10 alone. Extending the time of incubation to 18 h leads to an increased response to the complex, but it still reached only the level of CFP-10 alone. In vitro digestion with lysosomal enzymes cathepsin L and S at 2000:1 protein to enzyme ratio demonstrates rapid digestion of the individual proteins while the ESAT-6-CFP-10 complex is resistant. The data suggest that the natural complex of ESAT-6-CFP-10 is less amenable to antigen processing leading to a lower T cell response as compared with the individual proteins.

Characterization of a population of small macrophages in induced sputum of patients with chronic obstructive pulmonary disease and healthy volunteers

The inflammatory process in chronic obstructive pulmonary disease (COPD) is active mainly in the airways, but little is known about the properties of the inflammatory cells in this compartment. We have studied leucocytes in induced sputum of COPD patients compared to controls in order to uncover what types of macrophages might be involved in the disease. Sputum induction was performed by inhalation of nebulized sodium chloride solution. Leucocytes were isolated and stained with specific monoclonal antibodies for analysis in flow cytometry. Flow cytometry analysis revealed that a major portion of CD14+ macrophages in COPD has lower forward scatter, i.e. they are small macrophages. While in control donors these small macrophages accounted for 6.9% of all macrophages, the percentage of these cells in COPD was 45.7%. CD14 and HLA-DR expression was high on these small sputum macrophages while the large sputum macrophages expressed only low levels of these surface molecules, both in control donors and COPD patients. Small sputum macrophages of both control donors and COPD patients showed higher levels of constitutive tumour necrosis factor (TNF) compared to the large macrophages. TNF was inducible by lipopolysaccharide (LPS) preferentially in the small sputum macrophages in the control donors but there was no further induction in COPD patients. These data show that the small sputum macrophages are a major macrophage population in COPD and that these cells exhibit features of highly active inflammatory cells and may therefore be instrumental in airway inflammation in COPD.

Tolerance Induced by the Lipopeptide Pam3Cys Is Due to Ablation of IL-1R-Associated Kinase-1

Stimulation of the human monocytic cell line Mono Mac 6 with the synthetic lipopeptide (S)-(2,3-bis(palmitoyloxy)-(2RS)-propyl)-N-palmitoyl-(R)-Cys-(S)-Ser(S)-Lys(4)-OH, trihydrochloride (Pam(3)Cys) at 10 microg/ml induces a rapid expression of the TNF gene in a TLR2-dependent fashion. Preculture of the cells with Pam(3)Cys at 1 microg/ml leads to a reduced response after subsequent stimulation with Pam(3)Cys at 10 microg/ml, indicating that the cells have become tolerant to Pam(3)Cys. The CD14 and TLR2 expression is not decreased on the surface of the tolerant cells, but rather up-regulated. Analysis of the NF-kappaB binding in Pam(3)Cys-tolerant cells shows a failure to mobilize NF-kappaB-p50p65 heterodimers, while NF-kappaB-p50p50 homodimers remain unchanged. Pam(3)Cys-tolerant cells showed neither IkappaBalpha-Ser(32) phosphorylation nor IkappaBalpha degradation but MyD88 protein was unaltered. However, IRAK-1 protein was absent in Pam(3)Cys-induced tolerance, while IRAK-1 mRNA was still detectable at 30% compared with untreated cells. In contrast, in LPS-tolerized cells, p50p50 homodimers were induced, IRAK-1 protein level was only partially decreased, and p50p65 mobilization remained intact. It is concluded that in Mono Mac 6 monocytic cells, inhibition of IRAK-1 expression at the mRNA and protein levels is the main TLR-2-dependent mechanism responsible for Pam(3)Cys-induced tolerance, but not for TLR-4-dependent LPS-induced tolerance.