Systemic aspects of allergic disease: the role of the bone marrow

Bioinformatics analysis of PLA2G7 as an immune-related biomarker in COPD by promoting expansion and suppressive functions of MDSCs

BACKGROUND

Immune mechanism is involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, the exact immune pathogenesis still remains unclear. This study aimed to identify the immune-related biomarkers in COPD through bioinformatics analysis and its potential molecular mechanism.

METHODS

GSE76925 was downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were screened, and enrichment analysis was performed. Single sample gene enrichment analysis (ssGSEA) was conducted to score the infiltration levels of immune cells. Weighted gene co-expression network analysis (WGCNA) was applied to identify trait-related modules and to further determine the key module-related DEGs. Moreover, the correlations between the key genes and clinical parameters and infiltration levels of immune cells were analyzed. Furthermore, expression of the selected one key gene, PLA2G7, the frequency of MDSCs, and the expression of MDSCs-related immunosuppressive mediators were determined among healthy, smokers and COPD patients. Finally, effects of PLA2G7 abnormal expression on the frequency of MDSCs and the expression of MDSCs-related immunosuppressive mediators were examined.

RESULTS

A total of 352 DEGs were observed. These DEGs were mainly related to RNA metabolism and positive regulation of organelle organization. In addition, the black module was the most correlated with COPD. Six key genes (ADAMDEC1, CCL19, CHIT1, MMP9, PLA2G7, and TM4SF19) were identified between the black module and DEGs. Serum Lp-PLA2 and mRNA levels of PLA2G7, MDSCs, and MDSCs-related immunosuppressive mediators were found to be upregulated in COPD patients compared to the controls. The expression of PLA2G7 represented positive impact on the frequency of MDSCs and the expression of MDSCs-related immunosuppressive mediators.

CONCLUSION

PLA2G7 may serve as a potential immune-related biomarker contributing to the progression of COPD by promoting expansion and suppressive functions of MDSCs.

Dynamic change, influencing factors, and clinical impact of cellular components in human breast milk

BACKGROUND

Numerous cellular components have been well demonstrated in human breast milk. However, little is known about their dynamic change, influencing factors, and potential clinical impacts on infants.

METHODS

Sixty and forty-five healthy mother-infant pairs were enrolled in the colostrum group and mature milk group, respectively. Participants' demographic and clinical information were collected by questionnaires, and the infants were followed up until 6 months after birth through telephone interview. Colostrum and mature milk were collected, and the percentage of various cell components were determined by flow cytometric analysis.

RESULTS

The results showed that, the total cell numbers, and the percentages of some stem cells, including CD34+, CD117+, CD133+, CD90+, CD105+, and CD146+ cells, were different in colostrum and mature milk. Besides, participants' characteristics had influence on the cellular components. Finally, high-CD34+ cells in colostrum, as well as the high-CD133+ cells and low-CD105+ cells in mature milk were associated with a significantly increased risk of infantile eczema within their first 3 months after birth.

CONCLUSIONS

Our data showed a dynamic change of cellular components, identified some of their influencing factors and their potential clinical impacts on infantile eczema, which helps to better understand the cellular components in human breast milk.

IMPACT

Some stem cell markers were dynamically changed in human colostrum and mature milk. Different cellular components were shown to be influenced by different participants' characteristics. High percentage of CD34+ cells in colostrum, as well as high percentage of CD133+ cells and low percentage of CD105+ cells in mature milk, were associated with a significantly increased risk of infantile eczema within their first 3 months after birth. To our knowledge, this is the first study on the clinical impacts of stem cells on infantile diseases, which helps to give a better understanding of human breast milk.

Increased numbers of peripheral blood CD34+ cells in dogs with canine atopic dermatitis

BACKGROUND

The bone marrow may be involved in human atopic diseases, as shown by the release of CD34+ cells into the peripheral blood.

HYPOTHESIS/OBJECTIVES

The aim was to determine the numbers of CD34+ cells in atopic dogs.

ANIMALS

The following three groups of dogs were studied: 27 dogs with nonfood-induced atopic dermatitis (NFICAD); 16 dogs with nonallergic inflammatory diseases; and 13 healthy control dogs.

METHODS

Dogs with NFICAD were selected after fulfilment of Favrot's criteria and exclusion of other pruritic dermatoses, including flea infestation and adverse reaction to foods. The Canine Atopic Dermatitis Extent and Severity Index (CADESI)-03 and a Visual Analog Scale (VAS) score for pruritus were used to quantify clinical signs. A phycoerythrin-conjugated anticanine CD34 antibody was used to stain peripheral blood CD34+ cells, and these were enumerated using a flow cytometer. The CD34+ cell counts were compared between groups and tested (in the NFICAD group) for correlation with the severity of clinical signs.

RESULTS

The numbers of peripheral CD34+ cells in dogs with NFICAD (median 1.7) were statistically higher than in dogs with other nonallergic inflammatory diseases (median 1.0; P = 0.01) and healthy control dogs (median 0.9; P = 0.009). In dogs with NFICAD, there was no correlation between CD34+ cell numbers and CADESI-03 scores or owner-assessed pruritus (VAS score).

CONCLUSIONS AND CLINICAL IMPORTANCE

The results of this study suggest the possible involvement of CD34+ cells in dogs with NFICAD. The role of CD34+ cells in the aetiopathogenesis of canine atopic dermatitis remains to be determined.

Modulation of the effects of lung immune response on bone marrow by oral antigen exposure

Allergic airway inflammation is attenuated by oral tolerization (oral exposure to allergen, followed by conventional sensitization and challenge with homologous antigen), which decreases airway allergen challenge-induced eosinophilic infiltration of the lungs and bone marrow eosinophilia. We examined its effects on bone marrow eosinophil and neutrophil production. Mice of wild type (BP-2, BALB/c, and C57BL/6) and mutant strains (lacking iNOS or CD95L) were given ovalbumin (OVA) or water (vehicle) orally and subsequently sensitized and challenged with OVA (OVA/OVA/OVA and H₂O/OVA/OVA groups, resp.). Anti-OVA IgG and IgE, bone marrow eosinophil and neutrophil numbers, and eosinophil and neutrophil production ex vivo were evaluated. T lymphocytes from OVA/OVA/OVA or control H₂O/OVA/OVA donors were transferred into naïve syngeneic recipients, which were subsequently sensitized/challenged with OVA. Alternatively, T lymphocytes were cocultured with bone marrow eosinophil precursors from histocompatible sensitized/challenged mice. OVA/OVA/OVA mice of the BP-2 and BALB/c strains showed, relative to H₂O/OVA/OVA controls, significantly decreased bone marrow eosinophil counts and ex vivo eosinopoiesis/neutropoiesis. Full effectiveness in vivo required sequential oral/subcutaneous/intranasal exposures to the same allergen. Transfer of splenic T lymphocytes from OVA/OVA/OVA donors to naive recipients prevented bone marrow eosinophilia and eosinopoiesis in response to recipient sensitization/challenge and supressed eosinopoiesis upon coculture with syngeneic bone marrow precursors from sensitized/challenged donors.

In vivo studies on the immunotoxic effects of microcystins on rabbit

Microcystins (MCs) are the toxic molecules produced by common cyanobacterium in freshwater blooms. Their toxicities raise severe health issues in livestock and human beings. In current study, the immunotoxic effects of MC-LR were investigated in rabbit through evaluating the dynamics of white blood cell (WBC) numbers and cytokine production such as interleukin-3 (IL-3), IL-4, IL-6, interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α). MCs at the high dose (50 μg MC-LReq kg(-1) ) significantly induced increase in the WBC number but decrease in the Th1 (IFN-γ, TNF-α) and Th2 (IL-3, IL-4, IL-6) production. In the low dose group(12.5 μg MC-LReq kg(-1) ), the number of WBC and the production of IFN-γ, IFN-α, IL-4, IL-3, and IL-6 increased gradually in first 12 h, reach the peaks at 12 h, and dropped after 24 h. Significantly positive correlations were found between the cytokines production of IL-4 and IL-6, IFN-γ and IFN-α, or IL-4 and IFN-γ. In conclusion, MC-LR is able to disturb the rabbit immune system and there exists time-dose response relationship in the MC-LR-eliciting perturbation, which probably give a better insight into investigating the immunotoxicity mechanisms of MCs in vivo. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.

Lineage(-)Sca1+c-Kit(-)CD25+ cells are IL-33-responsive type 2 innate cells in the mouse bone marrow

IL-33 promotes type 2 immune responses, both protective and pathogenic. Recently, targets of IL-33, including several newly discovered type 2 innate cells, have been characterized in the periphery. In this study, we report that bone marrow cells from wild-type C57BL/6 mice responded with IL-5 and IL-13 production when cultured with IL-33. IL-33 cultures of bone marrow cells from Rag1 KO and Kit(W-sh/W-sh) mice also responded similarly; hence, eliminating the possible contributions of T, B, and mast cells. Rather, intracellular staining revealed that the IL-5- and IL-13-positive cells display a marker profile consistent with the Lineage(-)Sca-1(+)c-Kit(-)CD25(+) (LSK(-)CD25(+)) cells, a bone marrow cell population of previously unknown function. Freshly isolated LSK(-)CD25(+) cells uniformly express ST2, the IL-33 receptor. In addition, culture of sorted LSK(-)CD25(+) cells showed that they indeed produce IL-5 and IL-13 when cultured with IL-33 plus IL-2 and IL-33 plus IL-7. Furthermore, i.p. injections of IL-33 or IL-25 into mice induced LSK(-)CD25(+) cells to expand, in both size and frequency, and to upregulate ST2 and α(4)β(7) integrin, a mucosal homing marker. Thus, we identify the enigmatic bone marrow LSK(-)CD25(+) cells as IL-33 responsive, both in vitro and in vivo, with attributes similar to other type 2 innate cells described in peripheral tissues.

Interaction between adaptive and innate immune pathways in the pathogenesis of atopic asthma: operation of a lung/bone marrow axis

Atopic asthma is the most common form of asthma, particularly during childhood, and in many cases it persists into adult life. Although atopy is clearly a risk factor for development of this disease, only a small subset of subjects sensitized to aeroallergens express persistent symptoms, suggesting that additional pathogenic mechanisms are involved. Recent studies have implicated respiratory viral infections as key cofactors in asthma development in atopic patients. In relation to initial expression of the asthma phenotype in early childhood, it has been shown that although both atopic sensitization and early severe lower respiratory tract infections can operate as independent asthma risk factors, the persistence of asthma is most frequent among children who experience both insults, suggesting that the relevant inflammatory pathways interact to maximally drive disease pathogenesis. Importantly, it has been established that both these factors must be operative contemporaneously for these interactions to occur (ie, the interactions are likely to be direct). Recent studies on viral-induced asthma exacerbations in atopic children have provided a plausible mechanism for these interactions. Notably, it has been demonstrated that signals triggered during the innate immune response to the virus can lead to the release of large numbers of migrating high-affinity IgE receptor-bearing bone marrow-derived precursors of mucosal dendritic cells into the blood. The subsequent trafficking of these cells to the infected airway mucosa where dendritic cell turnover is very high provides a potential mechanism for recruitment of underlying aeroallergen-specific T-helper 2 immunity into the already inflamed milieu in the infected airway mucosa.

Interactions between innate and adaptive immunity in asthma pathogenesis: new perspectives from studies on acute exacerbations

Asthma is a complex multigenic disease. The most frequently encountered form is atopic asthma, which is at its highest prevalence during childhood/young adulthood, and this represents the main focus of this review. The primary risk factor for atopic asthma is sensitization to perennial aeroallergens resulting from a failure to generate protective immunologic tolerance. This tolerance process is orchestrated by airway mucosal dendritic cells and normally results in programming of regulatory T cells, which inhibit activation of the T(H)2 memory cells that, among other activities, drive IgE production and prime the effector populations responsible for IgE-mediated tissue damage. Emerging evidence highlights the complexity of this process, in particular the iterative nature of the underlying interactions between innate and adaptive immune mechanisms in which virtually every signal emanating from one cellular compartment provokes an answering response from the other. To further complicate this picture, the local mesenchyme can also interpose signals to fine tune immune responses to optimally meet local microenvironmental needs. Perturbation of the balance between these interlinked innate and adaptive immune pathways is increasingly believed to be the basis for disease expression, and in the specific case of atopic asthma, the prototypic example of this (discussed below) is acute exacerbations triggered by viral infections.

Induction of interleukin-4 production in neonatal IgE+ cells after crosslinking of maternal IgE

Transfer of maternal IgE antibodies to the neonate with the colostrum has been described in different mammalian species. Previous work in horses has shown that IgE bound to the surface of neonatal basophils is solely of maternal origin. However, the functional role of the maternal IgE transfer remained unclear. We hypothesized that maternal IgE mediates the onset of innate IL-4 production in equine neonatal basophils. Intracellular IL-4 production was measured in PBMC of newborn and older foals by flow cytometric analysis. A small population of IL-4(+) cells was observed in the peripheral blood at days 3-5 after birth. Phenotyping of the IL-4(+) cells showed that they were IgE(+)/MHCII(low)/CD4(-) cells. Magnetic cells sorting of the IgE(+)/MHCII(low) cells identified them as basophils. Anti-IgE stimulation in vitro induced IL-4 in IgE(+)/MHCII(low) basophils, but not in MHCII(+) cells or cells collected before colostrum ingestion. In conclusion, stimulation via maternal IgE antibodies mediated innate IL-4 production in neonatal basophils which might provide a paragenetic mechanism to promote the development of adaptive T-cell responses in the neonate after birth.

The influence of TSLP on the allergic response

Exposure to allergens first occurs at body surfaces in direct contact with the environment such as the skin, airways, and gastrointestinal tract, and compelling evidence suggests that allergic inflammatory responses are profoundly influenced by the products of epithelial cells located at these sites. One such product is thymic stromal lymphopoietin (TSLP), which is capable of affecting multiple cell lineages involved in allergic reactions. In this review we discuss recent work that has provided insight into the role TSLP plays in both aberrant and protective allergic inflammatory responses, as well as regulation, associations with disease, sources, and functions of this important cytokine.

Inducible nitric oxide synthase/CD95L-dependent suppression of pulmonary and bone marrow eosinophilia by diethylcarbamazine

RATIONALE

The mechanism of action of diethylcarbamazine (DEC), an antifilarial drug effective against tropical pulmonary eosinophilia, remains controversial. DEC effects on microfilariae depend on inducible NO synthase (iNOS). In eosinophilic pulmonary inflammation, its therapeutic mechanism has not been established. We previously described the rapid up-regulation of bone marrow eosinophilopoiesis in ovalbumin (OVA)-sensitized mice by airway allergen challenge, and further evidenced the down-regulation of eosinophilopoiesis by iNOS- and CD95L-dependent mechanisms.

OBJECTIVES

We investigated whether: (1) DEC can prevent the effects of airway challenge of sensitized mice on lungs and bone marrow, and (2) its effectiveness depends on iNOS/CD95L.

METHODS

OVA-sensitized BALB/c mice were intranasally challenged for 3 consecutive days, with DEC administered over a 12-, 3-, or 2-day period, ending at the day of the last challenge. We evaluated: (1) airway resistance, cytokine (IFN-gamma, IL-4, IL-5, and eotaxin) production, and pulmonary eosinophil accumulation; and (2) bone marrow eosinophil numbers in vivo and eosinophil differentiation ex vivo.

MEASUREMENTS AND MAIN RESULTS

DEC effectively prevented the effects of subsequent challenges on: (1) airway resistance, Th1/Th2 cytokine production, and pulmonary eosinophil accumulation; and (2) eosinophilopoiesis in vivo and ex vivo. Recovery from unprotected challenges included full responses to DEC during renewed challenges. DEC directly suppressed IL-5-dependent eosinophilopoiesis in naive bone marrow. DEC was ineffective in CD95L-deficient gld mice and in mice lacking iNOS activity because of gene targeting or pharmacological blockade.

CONCLUSIONS

DEC has a strong impact on pulmonary eosinophilic inflammation in allergic mice, as well as on the underlying hemopoietic response, suppressing the eosinophil lineage by an iNOS/CD95L-dependent mechanism.

Interactions between innate antiviral and atopic immunoinflammatory pathways precipitate and sustain asthma exacerbations in children

Severe asthma exacerbations in children requiring hospitalization are typically associated with viral infection and occur almost exclusively among atopics, but the significance of these comorbidities is unknown. We hypothesized that underlying interactions between immunoinflammatory pathways related to responses to aeroallergen and virus are involved, and that evidence of these interactions is detectable in circulating cells during exacerbations. To address this hypothesis we used a genomics-based approach involving profiling of PBMC subpopulations collected during exacerbation vs convalescence by microarray and flow cytometry. We demonstrate that circulating T cells manifest the postactivated "exhausted" phenotype during exacerbations, whereas monocyte/dendritic cell populations display up-regulated CCR2 expression accompanied by phenotypic changes that have strong potential for enhancing local inflammation after their recruitment to the atopic lung. Notably, up-regulation of FcepsilonR1, which is known to markedly amplify capacity for allergen uptake/presentation to Th2 effector cells via IgE-mediated allergen capture, and secondarily programming of IL-4/IL-13-dependent IL-13R(+) alternatively activated macrophages that have been demonstrated in experimental settings to be a potent source of autocrine IL-13 production. We additionally show that this disease-associated activation profile can be reproduced in vitro by cytokine exposure of atopic monocytes, and furthermore that IFN-alpha can exert both positive and negative roles in the process. Our findings suggest that respiratory viral infection in atopic children may initiate an atopy-dependent cascade that amplifies and sustains airway inflammation initiated by innate antiviral immunity via harnessing underlying atopy-associated mechanisms. These interactions may account for the unique susceptibility of atopics to severe viral-induced asthma exacerbations.

CD34+ hemopoietic progenitor cells are potent effectors of allergic inflammation

BACKGROUND

In steady state, hemopoietic progenitors constantly egress from the bone marrow (BM) into the blood and circulate through the peripheral tissues. In allergic diseases, the BM releases increased numbers of CD34(+) progenitor cells that migrate to the site of allergic inflammation, where they differentiate into tissue-dwelling and classic effector cells of allergy, such as mast cells, eosinophils, and basophils.

OBJECTIVE

To examine whether peripheral blood CD34(+) cells in addition to being progenitors may also directly function as inflammatory effector cells.

METHODS

Highly purified neonatal or adult blood CD34(+) cells were examined for the expression of thymic stromal lymphopoietin (TSLP) and IL-33 receptors and for their response to these cytokines as well as to supernatants of primary small airway epithelial cells and nasal explants from rhinosinusitis and control subjects. Sputum of patients with asthma was examined before and after allergen inhalation for the presence of IL-5 and IL-13-containing CD34(+) cells.

RESULTS

Circulating CD34(+) cells expressed receptors for TSLP and IL-33 and responded to these cytokines by rapidly releasing high levels of proinflammatory T(H)2-like cytokines and chemokines. These cells were activated in a TSLP-dependent manner by the supernatant fluids from activated primary human small airway epithelial cells and from nasal explants of patients with chronic rhinosinusitis. Moreover, activated CD34(+) cells containing IL-5 and IL-13 could be detected in the sputum of individuals with allergic asthma, with numbers increasing in response to specific allergen inhalation challenge.

CONCLUSION

Blood CD34(+) cells, in addition to being progenitors, may act as proinflammatory effector cells by themselves and directly contribute to the allergic inflammation.

Treatment with anti-CC chemokine receptor 3 monoclonal antibody or dexamethasone inhibits the migration and differentiation of bone marrow CD34 progenitor cells in an allergic mouse model

BACKGROUND

The migration and in situ differentiation of CD34(+) progenitors contribute to inflammatory eosinophilia in asthma and corticosteroids have been widely used in asthma. However, little is know about whether and how corticosteroids modulate the migration and differentiation of CD34(+) progenitors. This study was aimed to investigate the impact of anti-CC chemokine receptor 3 (CCR3) or dexamethasone on inflammatory eosinophilia in asthma and possible mechanism(s) underlying the action of dexamethasone or anti-CCR3 on migration and differentiation of CD34(+) progenitors in asthmatic context.

METHODS

Using an asthmatic mouse model, airway inflammation of anti-CCR3- or dexamethasone-treated mice and that of controls were characterized. And the migration and differentiation of CD34(+) progenitor cells were analyzed in vivo, ex vivo or in vitro.

RESULTS

Treatment with anti-CCR3 or dexamethasone significantly inhibited allergen-induced eosinophilia and CD34(+) progenitor cell infiltration in the lung, which was accompanied by lower levels of airway hyper-responsiveness and mucus production. Moreover, anti-CCR3 inhibited the eotaxin-mediated migration and IL-5/eotaxin-induced differentiation of CD34(+) progenitors in vitro. Dexamethasone was also shown to mitigate eotaxin-mediated migration and IL-5 or eotaxin-promoted differentiation of CD34(+) progenitor cells ex vivo, which were associated with the down-regulation of CCR3 expression on bone marrow progenitor cells.

CONCLUSIONS

Treatment with anti-CCR3 or dexamethasone can inhibit the migration and differentiation of CD34(+) progenitor cells by regulating the eotaxin/CCR3 axis in asthmatic mice. Our findings provide new insights into understanding the mechanism(s) underlying the action of dexamethasone and CCR3-mediated signaling in allergic inflammation and aid in the design of new immunotherapy for intervention of human asthma.

Cell-mediated immune response to unrelated proteins and unspecific inflammation blocked by orally tolerated proteins

Oral tolerance promotes a generalized decrease in specific immune responsiveness to proteins previously encountered via the oral route. In addition, parenteral immunization with a tolerated protein also triggers a significant reduction in the primary responsiveness to a second unrelated antigen. This is generally explained by 'innocent bystander suppression', suggesting that the transient and episodic effects of inhibitory cytokines released by contact with the tolerated antigen would block responses to the second antigen. In disagreement with this view, we have previously shown that: (i) these inhibitory effects do not require concomitance or contiguity of the injections of the two proteins; (ii) that intravenous or intragastric exposures to the tolerated antigen are not inhibitory; and (iii) that the inhibitory effect, once triggered, persists in the absence of further contact with the tolerated protein, possibly by inhibition of secondary responsiveness (immunological memory). The present work confirms that immunological memory of the second unrelated antigen is hindered by exposure to the tolerated antigen and, in addition, shows that this exposure: (i) inhibits the inflammation triggered by an unrelated antigen through the double effect of inhibiting production of leucocytes in the bone marrow and blocking their migration to inflammed sites; and (ii) significantly blocks footpaw swelling triggered by carrageenan. Taken together, these results conclusively demonstrate that inhibitory effects of parenteral injection of tolerated antigens are much more general than suggested by the 'innocent bystander suppression' hypothesis.

Vitamin A deficiency decreases and high dietary vitamin A increases disease severity in the mouse model of asthma

The Th1/Th2 paradigm has become an important issue in the pathogenesis of asthma, characterized by normal Th1 and elevated Th2 cytokine expression. Vitamin A deficiency (VAD) can produce a Th1 bias, whereas high-level dietary vitamin A can promote a Th2 bias. We used the OVA exposure mouse model to determine the contributions of vitamin A-deficient, control (4IU/g), and high-level vitamin A (250-IU/g) diets to the development of allergic airway inflammation and hyperresponsiveness. VAD reduced serum IgE and IgG1 responses, pulmonary eosinophilia, and the levels of IL-4 and IL-5 in bronchoalveolar lavage specimens, whereas the 250-IU/g diet increased serum IgE. Also, VAD blocked pulmonary hyperresponsiveness following methacholine challenge while the 250-IU/g diet exacerbated pulmonary hyperresponsiveness. In conclusion, VAD diminished and high-level dietary vitamin A enhanced the development of experimental asthma in this model system. These data suggest that excessive intake of vitamin A may increase the risk or severity of asthma in industrialized countries whereas vitamin A deficiency continues to increase mortality from infectious diseases in developing countries.

Expression of Toll-like receptor 9 in nose, peripheral blood and bone marrow during symptomatic allergic rhinitis

Background

Allergic rhinitis is an inflammatory disease of the upper airway mucosa that also affects leukocytes in bone marrow and peripheral blood. Toll-like receptor 9 (TLR9) is a receptor for unmethylated CpG dinucleotides found in bacterial and viral DNA. The present study was designed to examine the expression of TLR9 in the nasal mucosa and in leukocytes derived from different cellular compartments during symptomatic allergic rhinitis.

Methods

The study was based on 32 patients with seasonal allergic rhinitis and 18 healthy subjects, serving as controls. Nasal biopsies were obtained before and after allergen challenge. Bone marrow, peripheral blood and nasal lavage fluid were sampled outside and during pollen season. The expression of TLR9 in tissues and cells was analyzed using immunohistochemistry and flow cytometry, respectively.

Results

TLR9 was found in several cell types in the nasal mucosa and in different leukocyte subpopulations derived from bone marrow, peripheral blood and nasal lavage fluid. The leukocyte expression was generally higher in bone marrow than in peripheral blood, and not affected by symptomatic allergic rhinitis.

Conclusion

The widespread expression of TLR9 in the nasal mucosa along with its rich representation in leukocytes in different compartments, demonstrate the possibility for cells involved in allergic airway inflammation to directly interact with bacterial and viral DNA.

Cysteinyl leukotrienes: multi-functional mediators in allergic rhinitis

Cysteinyl leukotrienes (CysLTs) are a family of inflammatory lipid mediators synthesized from arachidonic acid by a variety of cells, including mast cells, eosinophils, basophils, and macrophages. This article reviews the data for the role of CysLTs as multi-functional mediators in allergic rhinitis (AR). We review the evidence that: (1) CysLTs are released from inflammatory cells that participate in AR, (2) receptors for CysLTs are located in nasal tissue, (3) CysLTs are increased in patients with AR and are released following allergen exposure, (4) administration of CysLTs reproduces the symptoms of AR, (5) CysLTs play roles in the maturation, as well as tissue recruitment, of inflammatory cells, and (6) a complex inter-regulation between CysLTs and a variety of other inflammatory mediators exists.

Systemic effects of oral tolerance on inflammation: mobilization of lymphocytes and bone marrow eosinopoiesis

Oral tolerance is a T-cell mediated phenomenon defined by inhibition of immune responsiveness to a protein previously contacted by the oral route. Oral tolerance may prevent autoimmune and allergic diseases that involve the recruitment and/or activation of different cell types including mast cells, neutrophils, eosinophils, monocytes and lymphocytes. The mechanisms by which oral tolerance avoids these immunological disorders are still controversial. Herein we used a murine model of ovalbumin (OVA)-induced peritonitis to investigate the effect of oral tolerance on allergic inflammation. Frequency of leucocyte subpopulations was evaluated by global and differential cell counts in peritoneal lavage fluid, peripheral blood, and bone marrow. Changes on lymphocyte subsets and adhesion molecules expression by these cells were analysed by flow cytometry. As compared with OVA-immune mice, intraperitoneal challenge of tolerant animals with OVA resulted in a significantly milder peritonitis, mostly affecting neutrophils and eosinophils; a concomitant reduction in total white blood cell counts was also observed, mainly because of lower neutrophil and eosinophil counts. Eosinophils, but not neutrophils, were also reduced in the bone-marrow of OVA-challenged tolerant mice. No changes occurred in total peritoneal lymphocyte counts in OVA-tolerant mice, however, there was a significant decrease in CD3+ CD8+ T cells and an increase in B cells (CD45R+) in these animals as compared to immune OVA-challenged animals. Altered expression of CD18 and CD54, respectively, in blood and peritoneal lymphocytes was also noted. These results suggest that, in addition to local specific effects, oral tolerance has systemic effects on the mobilization of leucocytes and bone-marrow eosinopoiesis.

Eicosanoids: mediators and therapeutic targets in fibrotic lung disease

Fibrosis is a common end-stage sequella of a number of acute and chronic lung diseases. Current concepts of pathogenesis implicate dysregulated interactions between epithelial cells and mesenchymal cells. Although investigative efforts have documented important roles for cytokines and growth factors in the pathogenesis of fibrotic lung diseases, these observations have not as yet been translated into efficacious therapies, and there is a pressing need for new pathogenetic insights and therapeutic approaches for these devastating disorders. Eicosanoids are lipid mediators derived from arachidonic acid, the most studied of which are the prostaglandins and leukotrienes. Although they are primarily known for their roles in asthma, pain, fever and vascular responses, present evidence indicates that eicosanoids exert relevant effects on immune/inflammatory, as well as structural, cells pertinent to fibrogenesis. In general, leukotrienes promote, whereas prostaglandin E(2) opposes, fibrogenic responses. An imbalance of eicosanoids also exists in pulmonary fibrosis, which favours the production of leukotrienes over prostaglandin E(2). This review highlights the role of this imbalance in the evolution of fibrotic lung disease, discusses the mechanisms by which it may arise and considers approaches for therapeutic targeting of eicosanoids in these conditions.

Cytokine expression in healthy and inflamed mucosa: probing the role of eosinophils in the digestive tract

BACKGROUND

In eosinophilic esophagitis (EE), the esophagus is infiltrated with activated eosinophils that often evoke tissue damage, but the intestines of these patients remain unaffected. We thus hypothesized that different tissue-dwelling eosinophil populations may coexist: activated eosinophils that infiltrate the esophagus and resting eosinophils that reside in unaffected intestines. We sought to characterize different eosinophil subpopulations by comparing the expression of certain proinflammatory proteins in tissue-dwelling eosinophils at different parts of the gastrointestinal tract.

METHODS

The 8 patients participating included 6 men and 2 women with a previously confirmed diagnosis of EE, whose average age was 39.4 years (range, 20-55 yr) and average disease duration was 13.6 years (range, 2-26 yr). Controls were 3 men and 1 woman, with a mean age of 43.3 years (range, 29-56 yr) with untreated functional dyspepsia who underwent diagnostic esophagogastroduodenoscopy. Six additional individuals having normal blood eosinophils were recruited for cytokine measurements in blood eosinophils. Immunofluorescence and immunoassays charted expression of CD25 and the TH2 cytokines, interleukin (IL)-4, IL-5, IL-10, and IL-13, in esophageal, intestinal, and blood eosinophils from controls and patients.

RESULTS

Controls showed a small but significant proportion of intestinal, but no blood, eosinophils expressing CD25 and IL-13, suggesting physiologic activation occurring in the digestive tract. On the other hand, eosinophils infiltrating the inflamed esophageal mucosa of patients with EE showed strong evidence of activation, with most expressing CD25, IL-4, and IL-13. Moreover, IL-13-positive intestinal eosinophils were increased in patients compared with controls.

CONCLUSIONS

We thus conclude that tissue-dwelling eosinophils show different and distinct cytokine expression patterns under noninflammatory and inflammatory conditions.

Effect of Mycobacterium vaccae on cytokine responses in children with atopic dermatitis

The increasing prevalence of atopic diseases over the last few decades is thought to be due to reduced exposure to environmental microbes that normally down-regulate allergic responses (hygiene hypothesis). We have shown previously that administration of the environmental microbe Mycobacterium vaccae ameliorates atopic dermatitis in school-age children at 3 months post-treatment. The present study tested the hypothesis that M. vaccae suppresses Th2-type cytokine activity and increases transforming growth factor (TGF)-beta(1) immunomodulatory activity in these children. Interleukin (IL)-4, IL-5, TGF-beta(1) and interferon (IFN)-gamma activity were assessed in resting and stimulated peripheral blood mononuclear cells (PBMC) isolated from 12 of the children who received M. vaccae in our original clinical trial. A cDNA expression array was used to examine a broader range of cytokine pathway transcripts. There were no significant changes in either Th2-type or TGF-beta(1) activity. A 5- to 10-fold increase in Th1-type activity was found at 1 month post-M. vaccae administration (P < 0.05), but it had returned to baseline by 3 months. The results do not support the hypothesis that M. vaccae reduces Th2-type or increases TGF-beta(1) activity of PBMC isolated from children with atopic dermatitis. The transient surge in IFN-gamma at 1 month is unlikely to explain any improvement in eczema score at 3 months.

Mast Cells, Basophils, and Eosinophils Acquire Constitutive IL-4 and IL-13 Transcripts during Lineage Differentiation That Are Sufficient for Rapid Cytokine Production

Mast cells, basophils, and eosinophils are myeloid cells that are distinguished by their capability to produce IL-4 and IL-13. However, it is not clear how this potential is related to the lineage differentiation of these subsets. In the present study we used bicistronic IL-4 reporter (4get) mice to directly visualize IL-4 expression by nonlymphoid cells in vitro and in vivo at the single-cell level. Our data show that frequent expression of both Il4 alleles is initiated and maintained during ontogeny by an IL-4Ralpha- or Stat6-independent mechanism. Despite the constitutive presence of cytokine transcripts in differentiated cells under steady state conditions, cytokine production is not detectable in the absence of stimulation. Moreover, mature mast cells, basophils, and eosinophils also constitutively express IL-13. Both preformed IL-4 and IL-13 mRNAs are sufficient for rapid cytokine production upon stimulation. Our data show that mast cells, basophils, and eosinophils are programmed for IL-4 and IL-13 expression early in ontogeny. These novel findings have important implications for the prevention and therapeutic intervention of allergic and asthmatic diseases.

Effects of a cysteinyl leukotriene receptor antagonist on eosinophil recruitment in experimental allergic rhinitis

The cysteinyl leukotrienes (cysLTs) are potent lipid mediators in allergic disease, acting through a receptor (cysLT1-R) which can be targeted in rhinitis and asthma. We investigated the effects of cysLT1-R antagonism in experimental allergic rhinitis, focusing on bone marrow eosinophil progenitor responses. BALB/c mice were sensitized, then given daily intranasal ovalbumin for 2 weeks, with montelukast sodium (5 mg/kg or 2.5 mg/kg) or placebo by gavage. Bone marrow eosinophil/basophil colonies were enumerated, and colony cells were morphologically assessed as indices of eosinophil differentiation and maturation. Montelukast treatment resulted in a significant decrease of eosinophils in the nasal mucosa, and in either bone marrow interleukin (IL)-5-, but not IL-3-, or granulocyte-macrophage colony-stimulating factor-responsive eosinophil/basophil colony-forming units, and IL-5-stimulated eosinophil maturation. These results indicate that cysLT1-R antagonism in vivo limits both IL-5-responsive eosinophilopoiesis, acting at several stages of eosinophil differentiation and maturation. The anti-allergic effects of cysLT1-R antagonists are consistent with the concept that cysLTs and IL-5 act together in the recruitment of eosinophils and eosinophil progenitors from the marrow during upper airway allergic inflammation.

The uptake kinetics and immunotoxic effects of microcystin-LR in human and chicken peripheral blood lymphocytes in vitro

Microcystin-LR is a cyanobacterial heptapeptide that presents acute and chronic hazards to animal and human health. We investigated the influence of this toxin on human and chicken immune system modulation in vitro. Peripheral blood lymphocytes were treated with microcystin-LR at environmentally relevant doses of 1, 10 and 25 microg/ml for 12, 24, 48, 72 h (for proliferation assay cells were treated for 72 h). T-cell and B-cell proliferation as well as apoptosis and necrosis were determined in human and chicken samples. IL-2 and IL-6 production by human lymphocytes also was measured. In addition, uptake kinetics of microcystin-LR into human and chicken peripheral blood lymphocytes were calculated by Liquid Chromatography (LS) /Mass Spectrometry (MS) analysis. At the highest dose microcystin-LR decreased T-cell proliferation and all doses of microcystin-LR inhibited B-cell proliferation. The frequency of apoptotic and necrotic cells increased in a dose and time-dependent manner. Human lymphocytes responded to stimulation with microcystin-LR by increased production of IL-6 and decreased production of IL-2. Human lymphocytes were able to uptake from 0.014 to 1.663 microg/ml and chicken lymphocytes from 0.035 to 1.733 microg/ml of the microcystin-LR added to the cultures, depending on the treatment time and dose. In conclusion, microcystin-LR acted as an immunomodulator in cytokine production and down-regulated lymphocyte functions by induction of apoptosis and necrosis. However, further studies dealing with the influence of microcystin-LR on expression cytokine genes and transcription factors are necessary to confirm these hypotheses.

Eosinophils and atopic dermatitis

In spite of the progress regarding the description of immunological phenomena associated with atopic dermatitis (AD), the pathogenesis of this disease still remains unclear. The presence of eosinophils in the inflammatory infiltrate of AD has long been established. Eosinophil numbers as well as eosinophil granule protein levels in peripheral blood are elevated in most AD patients and appear to correlate with disease activity. Moreover, eosinophil granule proteins, which possess cytotoxic activity, are deposited in the skin lesions. These observations indicate a role of eosinophils in the pathogenesis of AD. Furthermore, AD is associated with increased production of T helper 2 cytokines including interleukin (IL)-5, which specifically acts on eosinophils, resulting in accelerated eosinophilopoiesis, chemotaxis, cell activation, and delayed apoptosis. Therefore, IL-5 is an interesting target for experimental therapy in this inflammatory disorder of the skin. Such studies might result in new insights into the pathogenetic role of eosinophils in AD.

Resolution of late-onset asthma following high-dose chemotherapy

We describe a patient with moderately severe (British Thorax Society Step IV/V) asthma requiring regular inhaled and oral corticosteroids to control symptoms who experienced resolution of her asthma following high-dose chemotherapy and autologous stem cell transplantation for breast cancer. As far as the authors are aware this is the first reported case.

Mite antigens enhance ICAM-1 and induce VCAM-1 expression on human umbilical vein endothelium

Although sublingual allergen-specific immunotherapy has been proved to be effective in the treatment of allergic diseases, controversy surrounds the means by which such a local therapy can induce systemic immunological changes. Adhesion molecules are critical in the regulation of leukocyte traffic. It has been hypothesized that allergenic extract, administered locally, may induce an up-regulation of the mucosal vessel vascular adhesion molecules (CAMs) resulting in local recruitment of circulating inflammatory cells. In the present study we investigated whether the mite antigens, Der p1 and Der p2, can modulate CAM expression of human endothelial cells (HEC). To do this, slices of whole human umbilical cord vein underwent short-term (8 hours) cultures in the presence or absence of mite antigen (baseline, unstimulated controls). Cryostatic sections of the specimens were then evaluated immunohistochemically for expression of intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) molecules. The results revealed that while Der p1 is capable of significantly up-regulating ICAM-1 and VCAM-1 on HEC, Der p2 antigen moderately up-regulates ICAM-1 expression but is ineffective in modulating VCAM-1. Although preliminary, these results clearly support the hypothesis that at least some of the effects of sublingual immunotherapy may derive from inflammatory cell recruitment at the site of allergen release.

The potential role of allergen-specific sublingual immunotherapy in atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease associated with increasing prevalence, morbidity, and cost in developed Western countries. Frequently associated with respiratory allergy during adulthood, atopic dermatitis often represents the first phenotypic appearance of atopy in early childhood when the allergic 'march' starts and progressively moves toward food allergy, asthma, and rhinitis. At present, a consistent body of evidence supports the view that atopic dermatitis may represent the skin compartmentalization of a systemic allergic inflammation. Lymphocytes infiltrating early lesional skin express a T helper (Th) 2 pattern of cytokine secretion (increased levels of interleukin [IL]-4 and/or IL-13 and decreased levels of interferon-gamma) as well as the typical Th2-type chemokine receptor CCR4, specific to the thymus and activation-regulated chemokines. Keratinocytes from patients with atopic dermatitis produce thymic stromal lymphopoietin, a novel cytokine that supports the early lymphocyte development in mouse models, and activates dendritic cells involved in the pathogenesis of allergic diseases in humans. Increased levels of circulating hemopoietic precursor cells have been reported in atopic dermatitis, as in allergic asthma and rhinitis. Furthermore, the recognition of CD34+ hemopoietic precursor cells, and evidence for cellular differentiation/maturational events occurring within atopic dermatitis skin lesion infiltrates, are consistent with the recent reinterpretation of the Th2/Th1 paradigm, where Th2 cells appear to belong to the early stages and Th1 to the ultimate stages of a linear, rather than divergent, pattern of lymphoid differentiation. This more detailed understanding of the immunologic derangements contributing to the atopic dermatitis pathogenesis has led to growing interest in allergen-specific immunotherapy for the disease. Due to the complexity intrinsic to atopic dermatitis and the lack of consensus-based guidelines for standardized outcome measure, only eight studies are available in the literature for a qualitative evaluation of this treatment approach. Two of these studies were double blind and placebo controlled, and six were cohort studies. Immunotherapy was found to be effective in one controlled study and five observational reports. Uncertain results were provided by one low-powered, controlled study, and negative outcomes were raised by a unique study performed with oral immunotherapy, which is not an effective route of mucosal allergen administration. Thus, more efficacy studies are required before immunotherapy could be recommended for the routine treatment of atopic dermatitis. Allergen-specific sublingual immunotherapy, given its excellent safety profile and ability to interfere with the systemic aspects of allergic inflammation, appears a good potential candidate for the pathogenetic treatment of the disease.

Gene microarray analysis reveals interleukin-5-dependent transcriptional targets in mouse bone marrow

Interleukin-5 (IL-5) is a hematopoietic differentiation factor that promotes the development of mature eosinophils from progenitors in bone marrow. We present a multifactorial microarray study documenting the transcriptional events in bone marrow of wild-type and IL-5-deficient mice at baseline and in response to infection with Schistosoma mansoni. The microarray data were analyzed by a 4-way subtractive algorithm that eliminated confounding non-IL-5-related sequelae of schistosome infection as well as alterations in gene expression among uninfected mice. Among the most prominent findings, we observed 7- to 40-fold increased expression of transcripts encoding the classic eosinophil granule proteins (eosinophil peroxidase, major basic protein, the ribonucleases) together with arachidonate-15-lipoxygenase and protease inhibitor plasminogen activator inhibitor 2 (PAI-2), in the IL-5-producing, infected wild-type mice only. This was accompanied by increased transcription of genes involved in secretory protein biosynthesis and granule-vesicle formation. Interestingly, we did not detect increased expression of genes encoding eosinophil-related chemokine receptors (CCR1, CCR3) or members of the GATA or CCAAT/enhancer binding protein (C/EBP) transcription factor families. These data suggest that the IL-5-responsive progenitors in the mouse bone marrow are already significantly committed to the eosinophil lineage and that IL-5 promotes differentiation of these committed progenitors into cells with recognizable and characteristic cytoplasmic granules and granule proteins.

Allergen-induced fluctuation in CC chemokine receptor 3 expression on bone marrow CD34+ cells from asthmatic subjects: significance for mobilization of haemopoietic progenitor cells in allergic inflammation

There is increasing evidence that primitive progenitors migrate from the bone marrow (BM) via the peripheral circulation to tissue sites where they undergo in situ differentiation to provide a continued source of effector cells, such as eosinophils, during an allergic inflammatory response. To study mechanisms of progenitor cell mobilization in allergic reactions, we investigated fluctuations in the expression of the eotaxin receptor, CC chemokine receptor 3 (CCR3), on CD34+ cells from stable asthmatics following allergen (i.e. antigen) challenge. BM aspirates were taken from seven early responder (ER) and 10 dual responder (DR) asthmatics who, following antigen challenge developed only an early bronchoconstrictor response and an early and late- bronchoconstrictor response, respectively. Expression of CCR3 was detected on primitive (CD34+ cells) and eosinophil-lineage committed progenitors (CD34+ interleukin-5 receptor alpha-subunit+ cells) by flow cytometry and confirmed by co-localization of CCR3 messenger RNA to CD34 immunopositive cells using in situ hybridization. When preantigen levels were compared to 24-hr postantigen levels, significant increases in BM CD34+ CCR3+ cells were detected in DR, who also developed a significant sputum and blood eosinophilia and increased methacholine airway responsiveness. In contrast, a significant attenuation of BM CD34+ CCR3+ cells was observed in ER. In a dose-dependent manner eotaxin, but not interleukin (IL)-5, stimulated CD34+ progenitor cell migration in vitro. This migrational response to eotaxin was abrogated by anti-CCR3 monoclonal antibody and primed by preincubation with IL-5. We propose that fluctuations in CCR3 expression on human BM CD34+ cells may facilitate chemokine-mediated progenitor cell mobilization to the peripheral circulation and the resultant development of pulmonary eosinophilia, a cardinal feature of asthma.

Anti-IL-5 (mepolizumab) therapy induces bone marrow eosinophil maturational arrest and decreases eosinophil progenitors in the bronchial mucosa of atopic asthmatics

BACKGROUND

Eosinophils develop from CD34(+) progenitors under the influence of IL-5. Atopic asthmatic individuals have increased numbers of mature eosinophils and eosinophil pro-genitors within their bone marrow and bronchial mucosa. We have previously reported that anti-IL-5 monoclonal antibody treatment decreases total bone marrow and bronchial mucosal eosinophil numbers in asthma.

OBJECTIVE

Using an anti-IL-5 monoclonal antibody, we examined the role of IL-5 in eosinophil development within the bone marrow and bronchial mucosa in asthma.

METHODS

Blood, bone marrow, and airway mucosal biopsy specimens were examined before and after anti-IL-5 (mepolizumab) treatment of asthmatic individuals in a double-blind, placebo-controlled trial. Numbers of mature and immature eosinophils were measured by histologic stain (bone marrow myelocytes, metamyelocytes, and mature eosinophils), flow cytometry (bone marrow and blood CD34(+)/IL-5Ralpha(+) cells), enumeration of bone marrow-derived eosinophil/basophil colony-forming units in methylcellulose culture, and sequential immunohistochemistry and in situ hybridization (bronchial mucosal CD34(+)/IL-5Ralpha mRNA(+) cells).

RESULTS

Mepolizumab decreased mature eosinophil numbers in the bone marrow by 70% (P =.017) in comparison with placebo and decreased numbers of eosinophil myelocytes and metamyelocytes by 37% (P =.006) and 44% (P =.003), respectively. However, mepolizumab had no effect on numbers of blood or bone marrow CD34(+), CD34(+)/IL-5Ralpha(+) cells, or eosinophil/basophil colony-forming units. There was a significant decrease in bronchial mucosal CD34(+)/IL-5Ralpha mRNA(+) cell numbers in the anti-IL-5 treated group (P =.04).

CONCLUSION

These data suggest that anti-IL-5 therapy might induce partial maturational arrest of the eosinophil lineage in the bone marrow. The reduction in airway CD34(+)/IL-5 mRNA(+) cell numbers suggests that IL-5 might also be required for local tissue eosinophilopoiesis.

Anti-allergic therapies: effects on eosinophil progenitors

Marked eosinophilic infiltration is the typical inflammatory response associated with allergic inflammation. Previous research involving animal and human models has established a role for the eosinophil/basophil hematopoietic progenitor in a systemic process of allergic inflammation. In this article, we will review the evidence implicating eosinophil/basophil progenitors in this systemic response and will discuss the rationale for targeting this cell in the treatment of allergic disease. In this context, we discuss corticosteroid treatment of allergic diseases, such as asthma and its effects on hematopoietic mechanisms, the effects of therapies that inhibit the actions of cysteinyl leukotrienes, the effects of in vivo blockade of the eosinophil-active cytokine interleukin-5, and the effects of antihistamines on hematopoiesis. It is suggested that several anti-allergic therapies exert their beneficial effects on allergic inflammation by influencing eosinophil production systemically. Therefore, targeting the systemic hematopoietic response may provide additional, more beneficial, therapeutic effects.