Costimulation through B7-2 (CD86) is required for the induction of a lung mucosal T helper cell 2 (TH2) immune response and altered airway responsiveness

Blockade of CTLA-4 promotes airway inflammation in naive mice exposed to aerosolized allergen but fails to prevent inhalation tolerance

In subjects not developing allergy, inhalation of nonpathogenic protein antigens causes no harm and is associated with tolerance induction. Repeated exposure to aerosolized ovalbumin (OVA) likewise does not evoke airway inflammation and induces inhalation tolerance in experimental animals. The present study explored the role of the inhibitory T-cell receptor CTLA-4, in preventing inflammation and in establishing inhalation tolerance in response to a protein antigen. Naive BALB/c mice were injected intraperitoneally with anti-CTLA-4 monoclonal antibody or control immunoglobulin G (IgG) and exposed daily to aerosolized saline or OVA over 10 or 20 consecutive days. OVA-specific IgE levels and the inflammatory response in airway tissues were assessed 2 days after last exposure. The OVA-specific IgE response was also evaluated in mice subjected to a subsequent immunogenic OVA challenge 18 days after last aerosol exposure. Additional mice were made tolerant by 10 days of OVA aerosol exposure and were then subjected to an immunogenic OVA challenge combined with CTLA-4 blockade or control IgG treatment. Repeated inhalation of aerosolized OVA alone did not cause a pulmonary inflammatory response. In contrast, 10 days of OVA exposure combined with blockade of CTLA-4 led to development of eosinophilic lung infiltrates, BAL fluid eosinophilia, goblet cell hyperplasia and increased OVA-specific IgE. By 20 days of OVA exposure and blockade of CTLA-4, the inflammatory response remained. Mice exposed to aerosolized OVA for 10 days exhibited greatly reduced OVA-specific IgE responses to subsequent immunogenic OVA challenge. Blockade of CTLA-4 during the period of OVA aerosol exposure did not prevent this suppression of the OVA-specific IgE response. Neither did blockade of CTLA-4 during immunogenic OVA challenge alter the allergen-specific IgE response. Our results indicate that in vivo blockade of CTLA-4 modulates the initial immune response to a protein antigen allowing the development of allergen-induced airway inflammation in naive mice. However, this initial exaggerated immune response is followed by the induction of inhalation tolerance, demonstrating that CTLA-4 signalling is not decisive in this process. Our findings also show that once inhalation tolerance is established it may not be disrupted by blockade of CTLA-4.

Induction of Enhanced Immunity to Intestinal Nematodes Using IL-9-Producing Dendritic Cells

Dendritic cells can be considered natural adjuvants and are able to act as cellular vaccines to protect against disease. Adoptive transfer of Ag-pulsed bone marrow-derived dendritic cells (BMDCs) enhanced expulsion of the intestinal nematode, Trichinella spiralis, from the small intestine. IL 9 is a critical cytokine in protective immunity to intestinal nematode infection and is believed to enhance Th2 immune responses. Deriving dendritic cells from an IL-9 transgenic (IL-9t) mouse has enabled a detailed investigation of the importance of IL-9 during Ag presentation. Indeed, IL-9t dendritic cells significantly enhanced T cell proliferation and Th2 responses and, after adoptive transfer, enhanced parasite-specific IgG1 and intestinal mastocytosis in vivo, leading to accelerated expulsion of adult worms from the intestine. Overall, this paper demonstrates that dendritic cell vaccination can be used to successfully protect the host against intestinal nematode infection and suggests that IL-9 can act as a potent type 2 adjuvant during Ag presentation and the early stages of Th2 activation.

Dendritic cells in asthma: a function beyond sensitization

Allergic asthma is one of the most common chronic diseases in western society, characterized by variable airway obstruction, mucus hypersecretion and infiltration of the airway wall with T-helper type 2 (Th2) cells, eosinophils and mast cells. If we are to devise new causal therapies for this disease, it is important to elucidate how Th2 cells are activated and respond to intrinsically harmless allergens. Dendritic cells (DCs) are the most important antigen-presenting cells in the lung and are mainly recognized for their exceptional potential to generate a primary immune response and sensitization to aeroallergens. Much less attention has been paid to the role of DCs in established inflammation. Based on functional studies in a murine model for asthma, in this review article, we propose that DCs are essential for generating allergen-specific effector Th2 responses in ongoing inflammation in sensitized mice. A better understanding of the role of DCs in the maintenance of the inflammatory response to allergens in asthma should lead to new therapeutic approaches intervening at the top of the inflammatory cascade.

Genetic and respiratory tract risk factors for aspergillosis: ABPA and asthma with fungal sensitization

Allergic bronchopulmonary aspergillosis (ABPA) is a Th2 allergic hypersensitivity lung disease due to bronchial colonization of Aspergillus fumigatus that affects 1-2% of asthmatic and 7-9% of cystic fibrosis (CF) patients. We hypothesize that genetic risk factors predispose these patients to develop ABPA. We previously reported HLA-DR2 and DR5 restriction as a risk factor for the development of ABPA. We further propose that HLA-DR restriction is necessary but not sufficient for the development of ABPA. Recently, we reported that IL-4Rα single nucleotide polymorphisms (SNP) and in particular the ile75val SNP in the IL-4 binding region is another risk factor and is associated with increased sensitivity to IL-4 stimulation. It has been reported that the combination of IL-4Rα and IL-13 SNP, ile75val/arg110gln, is associated with more severe asthma. In preliminary studies, we have observed increased frequency of this combination in ABPA asthmatic and CF patients. Another genetic risk factor reported by Brouard et al. is the -1082 GG genotype in the IL-10 promoter in CF patients for the colonization of A. fumigatus and development of ABPA. This genotype was associated with increased plasma IL-10 levels, and perhaps may be associated with increased skewing of Th2 Aspergillus responses rather than down-regulation of inflammatory responses. We hypothesize that increased sensitivity of IL-4 mediated activities secondary to polymorphisms IL-4R in conjunction of other polymorphisms such as IL-13 and IL-10 in conjunction with HLA-DR2/DR5 restriction to Aspergillus antigens in ABPA patients result in increased B-cell activity, monocyte/dendritic cell phenotype that skews Th2 responses, and skewing of Aspergillus-specific Th2 cells. This model system may be applicable to other fungi such as Alternaria and Cladosporium which is associated with increased asthma severity.

CD28/CTLA-4--CD80/CD86 and ICOS--B7RP-1 costimulatory pathway in bronchial asthma

Costimulatory molecules are cell surface glycoproteins that can direct, modulate and fine-tune T-cell receptor signals. The B7-1/B7-2--CD28/CTLA-4 and ICOS-B7RP-1 pathway provides key second signals that can regulate the activation, inhibition and fine-tuning of T-lymphocyte responses. The expression of B7-1/B7-2--CD28/CTLA-4 molecules on clinical samples from patients with asthma have been well studied, and the results indicate that different extents of these molecules are expressed on the surface of various cells, and that the concentrations of soluble form of these molecules are elevated in the sera of patients with asthma. There is a burst of papers describing an important role for B7-1/B7-2--CD28/CTLA-4 pathway in the Th1/Th2 balance. Similarly, ICOS stimulates both Th1 and Th2 cytokine production but may have a preferential role in Th2 cell development. Moreover, The B7-1/B7-2-CD28/CTLA-4 and ICOS-B7RP-1 pathway has been suggested of being involved in the development of airway inflammation and airway hyperresponsiveness. Further study of the functions of the pathways within the CD28/CTLA-4--CD80/CD86 and ICOS--B7RP-1 superfamily individually and their interplay should provide insights into the pathogenesis of asthma, and has great therapeutic potential for treatment of asthma.

Allergic bronchopulmonary aspergillosis in a patient with cystic fibrosis: diagnostic criteria when the IgE level is less than 500 IU/mL

BACKGROUND

Recently, the Cystic Fibrosis Foundation developed a consensus report recommending diagnostic criteria for allergic bronchopulmonary aspergillosis (ABPA) in patients with cystic fibrosis that includes a serum IgE level greater than 500 IU/mL as the "minimal diagnostic criterion."

OBJECTIVE

To describe a 7-year-old girl with ABPA whose serum IgE level increased to only 398 IU/mL.

METHODS

Total IgE and anti-Aspergillus serologic measurements were performed using enzyme-linked immunosorbent assay and standard laboratory techniques; HLA analysis was performed; interleukin 4 receptor alpha single nucleotide polymorphisms were performed using polymerase chain reaction and DNA sequencing; CD23+ B cells were measured using flow cytometry; and cytokine synthesis to Aspergillus purified antigens was assessed using flow cytometry.

RESULTS

A 7-year-old girl with cystic fibrosis who had mild pulmonary disease and well-controlled asthma developed pulmonary infiltrates, increased wheezing, and decreased pulmonary function. Additional studies demonstrated peripheral blood eosinophilia (eosinophil count, 1807 cells/mm3 [19%]) and an increase in IgE and IgG anti-Aspergillus serology; bronchoalveolar lavage revealed septate hyphae with 45 degrees branching subsequently identified as A fumigatus and pulmonary eosinophilia. Previous HLA typing revealed that the patient was HLA-DR2+, DRB*1501, HLA-DQ2-, a pattern associated with increased risk of ABPA. In addition, there was increased up-regulation of CD23 molecules by interleukin 4 stimulation on the patient's B cells, as observed in ABPA. The patient was treated with corticosteroids and itraconazole with resolution of symptoms and pulmonary infiltrates.

CONCLUSIONS

Examination of the pulmonary inflammatory response using bronchoalveolar lavage, genetic risk with HLA-DR2+DQ2- typing, and increased interleukin 4 sensitivity are useful adjunctive studies in the diagnosis of ABPA.

The costimulatory molecules CD80, CD86 and OX40L are up-regulated in Aspergillus fumigatus sensitized mice

Aspergillus fumigatus (Af) is a fungus associated with allergic bronchopulmonary aspergillosis (ABPA) and other allergic diseases. Immune responses in these diseases are due to T and B cell responses. T cell activation requires both Af-specific engagement of the T-cell-receptor as well as interaction of antigen independent costimulatory molecules including CD28-CD80/CD86 and OX40-OX40L interactions. Since these molecules and their interactions have been suggested to have a potential involvement in the pathogenesis of ABPA, we have investigated their role in a model of experimental allergic aspergillosis. BALB/c mice were primed and sensitized with Af allergens, with or without exogenous IL-4. Results showed up-regulation of both CD86 and CD80 molecules on lung B cells from Af-sensitized mice (79% CD86+ and 24% CD80+) and Af/rIL-4-treated mice (90% CD86+ and 24% CD80+) compared to normal controls (36% and 17%, respectively). Lung macrophages in Af-sensitized mice treated or not with IL-4 showed enhanced expression of these molecules. OX40L expression was also up-regulated on lung B cells and macrophages from both Af-sensitized and Af/rIL-4 exposed mice as compared to normal controls. All Af-sensitized animals showed peripheral blood eosinophilia, enhanced total serum IgE and allergen-specific IgG1 antibodies and characteristic lung inflammation. The up-regulation of CD80, CD86 and OX40L molecules on lung B cells and macrophages from Af-allergen exposed mice suggests a major role for these molecules in the amplification and persistence of immunological and inflammatory responses in ABPA.

Interleukin-13-dependent bronchial hyper-responsiveness following isolated upper-airway allergen challenge in a murine model of allergic rhinitis and asthma

BACKGROUND

We have previously shown that isolated allergic sensitization and challenge of the upper airway results in lower-airway inflammation, which supports the concept of the united airways.

OBJECTIVE

This study investigates the hypothesis that isolated upper-airway allergic sensitization is sufficient to induce bronchial hyper-responsiveness (BHR), characteristic of asthma, and that IL-13 is an essential mediator in both the upper and lower airways.

METHODS

BALB/c mice were sensitized and challenged by intranasal instillation of allergen ovalbumin (OVA) using our standard protocol. BHR to methacholine was determined and inflammation in nares and lung was assessed.

RESULTS

Isolated intranasal application of allergen in awake animals resulted in almost exclusive deposition in the upper airways while in anaesthetized mice there was almost equal distribution in the upper and lower airways. We have demonstrated significant BHR to methacholine challenge in animals receiving OVA only in the upper airway. Also noted was concomitant increase in eosinophilic infiltrates in lung and nares as well as increased granulocytes and IL-13 levels in bronchoalveolar lavage (BAL) fluid. Using a polyclonal anti-IL-13 antibody we have shown inhibition of airways inflammation, both in nares and in lung with significant reduction of granulocytes in BAL from anti-IL-13 treated mice (P<0.0001). Anti-IL-13 treatment also abrogates allergen-induced BHR (P<0.01).

CONCLUSION

These data suggest that isolated upper-airway allergen deposition initiates allergic responses along the entire airway. IL-13 mediates both airway inflammation and BHR and may play a role in the communication between the upper and lower airways.

Increased expression of plasma and cell surface co-stimulatory molecules CTLA-4, CD28 and CD86 in adult patients with allergic asthma

The co-stimulatory interactions of the B7 family molecules CD80 and CD86 on antigen-presenting cells, together with their T cell counter receptors CD28 and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), modulate T lymphocyte-mediated immune responses in a reciprocal manner. To investigate whether there is altered expression and the clinical significance of soluble co-stimulatory molecules in asthmatic patients, plasma concentrations of sCTLA-4, sCD28, sCD80 and sCD86 in 51 adult allergic asthmatic adults with or without steroid treatment, and 35 sex- and age-matched control subjects were measured by enzyme-linked immunosorbent assay (ELISA). Cell surface expression of CTLA-4 and CD28 on peripheral blood mononuclear cells (PBMC) were analysed by flow cytometry. Results showed that the plasma sCTLA-4 concentration was significantly higher in all asthmatic patients while sCD28 and sCD86 concentrations were significantly higher in steroid and non-steroid treated asthmatic patients, respectively, compared with control subjects (all P < 0.01). Significantly increased cell surface expression of CD28 but not CTLA-4 on PBMC was found in asthmatic patients compared with controls (P < 0.05). The plasma concentration and cell surface expression of CTLA-4 were found to exhibit positive and significant correlations with those of CD28 (both P < 0.05). Serum total IgE concentration correlated positively and significantly with sCTLA-4 and sCD28 concentrations in allergic asthmatic patients (both P < 0.05). The increased expression of these soluble co-stimulatory molecules may reflect the dysregulation of T cell activation, thereby contributing to the immunopathogenesis of allergic asthma.

Costimulation: critical pathways in the immunologic regulation of asthma

T cells play an important role in the pathogenesis of allergy and asthma. T-cell receptor engagement by antigenic peptides presented to major histocompatibility complex (MHC) class II molecules and activation of costimulatory molecules are crucial in the regulation of T-cell immune responses. Costimulatory molecules are responsible for second signals that induce T-cell activation and proliferation. The best characterized costimulatory pathways include CD80/CD86 interacting with CD28, and a number of additional costimulatory molecules have recently been identified, including members of the tumor necrosis family. The positive signals induced by these molecules are counterbalanced by other members of the costimulatory family, including cytotoxic T lymphocyte-associated antigen (CTLA)-4, programmed death (PD)-1, and B and T lymphocyte attenuator (BTLA), which dampen immune responses. In this review, we describe the fundamental properties of costimulatory molecules and address the influence of costimulatory signals on allergic responses.

Elevation of plasma soluble T cell costimulatory molecules CTLA-4, CD28 and CD80 in children with allergic asthma

BACKGROUND

The surface expression of T cell costimulatory molecules CTLA-4 and CD28 and their counter-ligands, B7 molecules (CD80, CD86), is differentially induced for T cell activation and expansion in allergic asthma. However, the role of their soluble forms in plasma has not yet been elucidated. In this study, we investigated whether expression is altered and whether soluble costimulatory molecules are clinically relevant in asthmatic patients.

METHODS

Plasma concentrations of soluble CTLA-4 (sCTLA-4), CD28, CD80 and CD86 in 51 children with chronic allergic asthma with or without inhaled corticosteroid treatment, and 22 sex- and age-matched control subjects were measured by enzyme-linked immunosorbent assay. Plasma total IgE concentration was measured using a microparticle immunoassay.

RESULTS

Asthmatic patients had higher logarithmic plasma total IgE concentration (IgE(log)) than healthy subjects (p < 0.0001). In non-steroid-treated patients, plasma sCTLA-4, sCD28 and sCD80 but not sCD86 concentrations were significantly higher than those of control subjects (all p < 0.05). Plasma sCD80 and sCD86 but not sCTLA-4 and sCD28 concentrations correlated significantly with IgE(log) of all subjects (p < 0.05). There were also significant positive correlations between sCTLA-4 and sCD28 (p = 0.0007), and between sCD80 and sCD86 in all asthmatic patients (p = 0.001).

CONCLUSIONS

Plasma sCTLA-4, sCD28 and sCD80 concentrations are elevated in allergic asthma. The increased expression of these soluble proteins may reflect the dysregulation of T cell activation, contributing to the immunopathogenesis of allergic asthma.

Soluble CD86 protein in serum samples of patients with asthma

BACKGROUND

Previous studies have reported that soluble (s) CD86 is involved in the initiation of the immune response. A study was undertaken to investigate the concentrations of sCD86 in serum samples from patients with bronchial asthma and to determine the cell origin of sCD86.

METHODS

Serum sCD86 concentrations were measured in 52 asthmatic subjects and 25 non-atopic normal volunteers using an enzyme linked immunosorbent assay, and the relationship of serum sCD86 concentrations to asthma severity and to total and differential white cell counts was analysed. Each type of white blood cell was purified and cultured in vitro to determine the cell origin of serum sCD86.

RESULTS

Serum samples from patients with an acute asthma exacerbation had much higher levels of sCD86 (585.4 (20.5) IU/ml) than those from stable asthmatics (479.6 (15.7) IU/ml, p<0.001) and healthy individuals (435.1 (13.8) IU/ml, p<0.001), and there was no difference between the latter two groups (p = 0.079). In asthmatic subjects the serum sCD86 level was inversely correlated with airway responsiveness, forced expiratory volume in 1 second, and with arterial carbon dioxide tension. In addition, the serum sCD86 level was positively correlated with numbers of lymphocytes, eosinophils, monocytes, but not neutrophils. The in vitro experiments indicated that sCD86 was produced by monocytes.

CONCLUSIONS

The serum sCD86 protein level was significantly increased in asthmatic subjects during an exacerbation and correlated with the severity of asthma. sCD86 is most probably derived from monocytes in the peripheral blood.

Immunopathogenesis of allergic bronchopulmonary aspergillosis in cystic fibrosis

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity lung disease mediated by an allergic late-phase inflammatory response to Aspergillus fumigatus antigens. ABPA is characterized by markedly elevated Aspergillus-specific and total IgE levels and eosinophilia, and manifested by wheezing, pulmonary infiltrates, and bronchiectasis and fibrosis, which afflict asthmatic and cystic fibrosis (CF) patients. We propose that ABPA develops in genetically susceptible CF patients due to HLA-DR2 and DR5 restriction, increased sensitivity to IL-4 stimulation, and increased A. fumigatus allergen-specific Th2 CD4+ T-cell-mediated responses. In addition, A. fumigatus proteases play a role in facilitation of antigen transport across the epithelial cell layer by damaging the epithelial integrity and by a direct interaction with epithelial cell surface receptors, resulting in pro-inflammatory cytokine production and corresponding inflammatory responses.

Importance of the inducible costimulator molecule for the induction of allergic immune responses and its decreased expression on T helper cells after venom immunotherapy

The inducible costimulator (ICOS), a newly identified member of the CD28 receptor family that is induced after T-cell activation, and its ligand (ICOSL), being expressed on activated monocytes and dendritic cells play a key role in T-cell-mediated immune responses. As ICOS costimulation also seems to regulate T helper 2 effector cells, the aim of this study was to analyse the function of this molecule in allergic immune responses and their specific therapy, mainly venom immunotherapy (VIT). CD4+ T cells from grass pollen-, or bee or wasp venom-allergic donors were stimulated in the presence of autologous mature dendritic cells, which were pulsed with different allergen doses. In this system, costimulation of ICOS strongly enhanced the production of the T helper 2 cytokines interleukin (IL)-4, IL-5 and IL-10 and, to a lesser extent, secretion of the T helper 1 cytokine, interferon-gamma. Expression of ICOS on CD4+ T cells was induced, in a dose-dependent manner, after a few days of stimulation with allergen-pulsed dendritic cells, reaching a peak on day 6. The upregulation of ICOS after stimulation with venom allergens was significantly reduced after VIT. Addition of exogenous IL-10 (which is induced during VIT) to the co-cultures before VIT also led to an inhibition of ICOS expression, while blocking of IL-10 in co-cultures after VIT partially restored the expression of ICOS. These data indicate that the inhibition of T cells after immunotherapy also involves decreased induction of the costimulatory molecule ICOS, which, in turn, seems to be dependent on the presence of IL-10, also associated with the inhibited status of T cells after VIT. This makes the ICOS-ICOSL pathway a potential target for therapeutic intervention in T helper 2-mediated diseases, such as allergic diseases.

B7-DC regulates asthmatic response by an IFN-gamma-dependent mechanism

B7-H1 (PD-L1) and B7-DC (PD-L2) are the ligands for programmed death-1 (PD-1), which is a member of the CD28/CTLA-4 family and has been implicated in peripheral tolerance. We investigated the roles of B7-H1 and B7-DC in a murine OVA-induced allergic asthma model. B7-H1 was constitutively expressed on dendritic cells, macrophages, B cells, and T cells in the lungs of naive mice, and its expression could be dramatically increased after allergen challenge. In contrast, B7-DC expression was scarcely expressed on dendritic cells in naive mice, but was up-regulated after allergen challenge, although the up-regulation of B7-DC expression on macrophages was minimal. Treatment of mice with anti-B7-DC mAb at the time of allergen challenge, but not at the time of sensitization, significantly increased their airway hyper-reactivity and eosinophilia. Such treatment also resulted in the increased production of IL-5 and IL-13, and decreased IFN-gamma production in the lungs and draining lymph node cells. These changes were diminished when mice were depleted of IFN-gamma by anti-IFN-gamma mAb pretreatment. Interestingly, treatment with anti-B7-H1 or anti-PD-1 mAb did not significantly affect the asthmatic response. These results suggest a unique role for B7-DC in the regulation of asthmatic response through an IFN-gamma-dependent, but PD-1-independent, mechanism.

Expression of genes for B7-H3 and other T cell ligands by nasal epithelial cells during differentiation and activation

Epithelial cells of the human respiratory tract express human leukocyte antigen (HLA) and the costimulatory molecules B7-1 and B7-2. Little is known, however, about the constitutive expression of genes encoding for the more recently identified members of the B7 homolog family of costimulatory molecules or about the influence of cellular differentiation and cytokines on their activity or on that of HLA or B7-1 and B7-2. Human nasal epithelial (HNE) cells were grown at the air-liquid interface (ALI) for 2 or 21 days to model in vivo conditions. Expression of genes for HLA-B and HLA-DR1 increased during mucociliary differentiation during this period and became more similar to HNE cells obtained fresh by brush biopsy from nasal turbinates. Gene transcripts for B7-H3 and B7-H2 were abundantly expressed in cells cultured at the ALI, but neither their activities nor that of B7-2 was significantly altered during differentiation. IFN-gamma and TNF-alpha upregulated mRNA encoding for both HLA molecules, but not for the B7 molecules. This study describes, for the first time, the expression of B7-H3 and B7-H2 by HNE cells and thus expands the range of potential costimulatory signals through which these cells may interact with activated mucosal T lymphocytes. In addition, the results suggest that the extent of mucociliary differentiation of cultured cells may influence this capability.

Why are dendritic cells important in allergic diseases of the respiratory tract?

Increasing evidence points to the role of antigen-presenting dendritic cells (DC) in regulating adaptive immune responses. DC are especially sensitive to signals derived from microbes, allergens, and the airway tissue microenvironment, can polarize naïve T-cells into either Th1 or Th2 effector cells, and are increasingly recognized as having a central role in the establishment of T-cell memory and tolerance to inhaled antigens. DC form a closely meshed network within the respiratory mucosa and are rapidly recruited from the circulation in response to a variety of proinflammatory stimuli. Studies using animal models have highlighted the role of DC in both initiation and maintenance of allergic airway inflammation. Increased numbers of airway mucosal DC are found in both allergic rhinitis and asthma, and an increasing number of investigators have highlighted important functional differences between DC from atopic and normal individuals. This article reviews recent information on the involvement of DC in the pathogenesis of allergic airway disease and the means by which DC could be exploited as targets for therapy in asthma and allergic rhinitis.

The role of ICOS and other costimulatory molecules in allergy and asthma

Activation and differentiation of T cells play a critical role in the pathogenesis of allergies and asthma. Upon encounter with specific antigen, naïve T helper precursor (ThP) cells become activated, an event that is regulated not only by engagement of the T cell receptor (TCR) with peptide presented in the context of MHC class II molecules, but also by a number of costimulatory signals. CD28 engagement by B7-1 and B7-2 on resting ThP cells provides a critical signal for initial cell cycle progression, interleukin-2 production and clonal expansion. However, in recent years, other related members of the immunoglobulin (Ig) family, such as inducible costimulatory molecules (ICOS) and the TNF receptor family members which include OX40, have also been demonstrated to play an important role in providing unique and complementary signals that regulate the outcome of immune responses. These positive costimulatory signals are counterbalanced by signals that dampen down immune responses and include CTLA-4, PD-1 and the recently described Ig superfamily members BTLA and TIM-3. This review discusses the role of these costimulatory signals and their potential involvement in the pathogenesis of asthma and allergic responses.

Increased sensitivity to IL-4 in cystic fibrosis patients with allergic bronchopulmonary aspergillosis

BACKGROUND

Allergic bronchopulmonary aspergillosis (ABPA) is characterized by a heightened Th2 CD4+ T-cell response to Aspergillus fumigatus allergens and a hyper-immunoglobulin (Ig)E state compared with cystic fibrosis patients without ABPA. We hypothesize that one reason for this response is increased sensitivity to interleukin (IL)-4 in ABPA resulting in increased expression of CD23 and CD86 and leading to a positive amplification mechanism that increases Th2 CD4+ T cell responses.

METHODS

Peripheral blood mononuclear cells (PBMC) were isolated from seven ABPA CF and 19 non-ABPA CF patients and 16 nonatopic controls and stimulated with rIL-4 (range 0.1-10 ng/ml) and rIL-13 (range 1-10 ng/ml) for 48 h. The number of CD23 molecules and percentages of CD23+ B cells were quantified by flow cytometry. Both phorbol 12-myristate 13-acetate (PMA)/ionomycin (IO) and antigen stimulated, toxoid and Asp f2/f3/f4, PBMC were examined for cytoplasmic cytokine synthesis enumerated by cytokine staining using flow cytometry to measure Th2 and Th1 CD3+ T cells.

RESULTS

The numbers of CD23 molecules on B-cells were significantly elevated at time 0 in ABPA CF patients compared with both non-ABPA CF patients and nonatopic controls. Following IL-4 stimulation in vitro, the numbers and percentages of CD23 expression on B cells were significantly up-regulated in ABPA CF patients compared with non-ABPA CF patients and controls. The IL-13 stimulation up-regulated CD23 expression; however, there was no significant difference in ABPA CF patients compared with non-ABPA CF patients and controls. The percentages of interferon (IFN)-gamma+ CD3+T cells following PMA/IO stimulation were significantly decreased in both ABPA and non-ABPA CF patients compared with controls. There were no significant differences of IL-4+ and IL-13+ CD3+ T cells between ABPA and non-ABPA CF patients. When tetanus toxoid stimulated T cells were examined, both ABPA and non-ABPA CF patients had significantly decreased IFN-gamma+ CD3+ T cells compared with controls. In Asp f2/f3/f4 stimulated T cells, ABPA CF patients had significantly increased IL-4+ CD3+ T cells compared with non-ABPA CF patients and controls.

CONCLUSIONS

ABPA CF patients have increased sensitivity to IL-4 but not to IL-13 up-regulation of CD23 molecules compared with non-ABPA CF patients. There were decreased percentages of IFN-gamma+ and IL-2+ Th1 T cells in CF patients compared with nonatopic controls but similar percentages of IL-4+ Th2 T cells in all three groups. However, ABPA CF patients had increased frequency of Aspergillus-stimulated Th2 T cells. This indicated that there is skewing of Th2 T cells in ABPA CF patients. Thus, in CF ABPA patients there is increased Th2 T cells and increased sensitivity to IL-4.

Etiopathogenesis and Management of Perennial Allergic Rhinitis

Perennial allergic rhinitis is an inflammatory disorder characterized by symptoms of nasal congestion, rhinorrhea, sneezing, and itching. The prevalence of allergic rhinitis is quite common and affects 20% or more of various populations. Some patients with allergic rhinitis are symptomatic only during the pollen season, while many others are allergic to multiple allergens including indoor allergens such as house dust mites, animal dander, cockroaches, and fungi, which lead to perennial symptoms. Immunoglobulin (Ig)-E is the proximate cause of perennial allergic rhinitis. Circulating IgE antibodies bind to the high affinity IgE receptor on mast cells and basophils. IgE antibodies, bound to the receptors crosslinked by allergen, initiate the secretion of inflammatory mediators including histamine, leukotrienes, and cytokines. These mediators can induce both acute and chronic changes that result in symptoms of allergy. Many therapies are approved for the treatment of allergic rhinitis including intranasal corticosteroids, antihistamines with or without decongestants, and nasal cromolyn sodium (sodium cromoglicate). Allergen avoidance is the mainstay of therapy for many patients but is not always practical. For those patients who have not responded to appropriate medications, allergen specific immunotherapy may also be effective.A number of studies with omalizumab have shown that it is effective in the treatment of seasonal allergic rhinitis induced by pollen such as ragweed and birch pollen. Omalizumab is a molecularly cloned humanized monoclonal antibody inhibiting human IgE. It binds specifically to the region of the IgE molecule that binds to the IgE receptor on the mast cell or basophils. Because omalizumab cannot bind IgE molecules that are already bound to the surface receptors on mast cells and basophils, it does not stimulate secretion of mediators from these cells. Omalizumab does not appear to stimulate an immune response against itself. It rapidly reduces free serum IgE levels by over 95% when administered at therapeutic doses and also results in the reduction of IgE receptors on mast cells and basophils. The combined effects of reduction of both free IgE in serum and the receptor density on the mast cells or basophils results in decreased allergen-stimulated mediator release. Preliminary studies in the treatment of perennial allergic rhinitis supports omalizumab's efficacy and safety. The compound has been well tolerated. Aside from urticarial reactions, adverse effects appear to be minimal. Omalizumab is the first of several new immune-based specifically targeted molecules that may prove to be extremely valuable in the treatment of perennial allergic rhinitis, as it is often unresponsive to traditional therapies.

Continuous exposure to house dust mite elicits chronic airway inflammation and structural remodeling

It is now fully appreciated that asthma is a disease of a chronic nature resulting from intermittent or continued aeroallergen exposure leading to airway inflammation. To investigate responses to continuous antigen exposure, mice were exposed to either house dust mite extract (HDM) or ovalbumin intranasally for five consecutive days, followed by 2 days of rest, for up to seven consecutive weeks. Continuous exposure to HDM, unlike ovalbumin, elicited severe and persistent eosinophilic airway inflammation. Flow cytometric analysis demonstrated an accumulation of CD4+ lymphocytes in the lung with elevated expression of inducible costimulator a marker of T cell activation, and of T1/ST2, a marker of helper T Type 2 effector cells. We also detected increased and sustained production of helper T cell Type 2-associated cytokines by splenocytes of HDM-exposed mice on in vitro HDM recall. Histologic analysis of the lung showed evidence of airway remodeling in mice exposed to HDM, with goblet cell hyperplasia, collagen deposition, and peribronchial accumulation of contractile tissue. In addition, HDM-exposed mice demonstrated severe airway hyperreactivity to methacholine. Finally, these responses were studied for up to 9 weeks after cessation of HDM exposure. We observed that whereas airway inflammation resolved fully, the remodeling changes did not resolve and airway hyperreactivity resolved only partly.

Leishmanial infection: analysis of its first steps. A review

The first steps in leishmaniasis are critical in determining the evolution of the disease. Major advances have recently been done in understanding this crucial moment. Fundamental research in parasite-vector interaction, parasite biology, insect saliva, and vertebrate host response have shed new light and uncovered a most fascinating and complex moment in leishmaniasis. We review here some of these aspects and we try to connect them in a logical framework.

CD28/CTLA4 double deficient mice demonstrate crucial role for B7 co-stimulation in the induction of allergic lower airways disease

BACKGROUND

The existence of a third B7-1/B7-2 receptor was postulated in a recent study using a novel mouse strain lacking both CD28 and CTLA4 (CD28/CTLA4-/-).

OBJECTIVE

In the present study, it was investigated if T cell co-stimulation via the putative B7-1/B7-2 receptor plays a role in the induction of Th2-mediated asthma manifestations in mice.

METHODS

BALB/c wild-type, CD28/CTLA4-/- and B7-1/B7-2-/- mice were sensitized and aerosol challenged with ovalbumin (OVA).

RESULTS

At 24 h after the last aerosol, wild-type mice showed airway hyper-responsiveness in vivo and up-regulated levels of serum OVA-specific IgE compared with the situation shortly before OVA challenge. In addition, eosinophil numbers and IL-5 levels in the broncho-alveolar lavage fluid and Th2 cytokine production by lung cells upon OVA re-stimulation in vitro were observed. In agreement with an earlier study, we failed to induce any of the asthma manifestations in B7-1/B7-2-/- mice. Importantly, also CD28/CTLA4-/- mice showed no asthma manifestations upon OVA sensitization and challenge.

CONCLUSION

These data clearly demonstrate that T cell co-stimulation via the putative B7-1/B7-2 receptor appears to have no role in the induction of Th2-mediated asthma manifestations in this murine model and, conversely, that CD28 signalling is crucial.

Airway dendritic cells: co-ordinators of immunological homeostasis and immunity in the respiratory tract

The large quantities and complex mixtures of antigens encountered daily at airway mucosal and alveolar surfaces pose a major challenge to maintenance of immunological homeostasis in the respiratory tract. Amongst this myriad of antigens, the immune system must discriminate between innocuous components that can be tolerated by the host and potentially life-threatening pathogens that require a rapid immune response. Dendritic cells (DC) represent the principal cell type at these sites capable of processing antigens and delivering signals that initiate tolerogenic or immunogenic immune responses. This review will discuss the role of DC at the "front-line" of immune surveillance and homeostasis within the respiratory tract and their role in the pathogenesis of respiratory disease.

Laboratory animal allergy: an update

Allergic reactions are among the most common conditions affecting the health of workers involved in the care and use of research animals. Between 11 and 44% of the individuals working with laboratory animals report work-related allergic symptoms. Of those who become symptomatic, 4 to 22% may eventually develop occupational asthma that can persist even after exposure ceases. Allergic symptoms consist of rashes where animals are in contact with the skin, nasal congestion and sneezing, itchy eyes, and asthma (cough, wheezing, and chest tightness). The generation of immunoglobulin E (IgE) antibodies is a prerequisite for the production of allergic symptoms. The mechanism by which IgE antibodies develop is becoming clearer. The propensity to produce IgE is genetically determined, and pre-existing allergy may be a risk factor for the development of laboratory animal allergy (LAA). However, exposure to animal allergens is the major risk factor for the development of LAA. Techniques to measure the airborne concentration of laboratory animal allergens have been developed. Research on animal allergens themselves indicates that many of the mouse and rat urinary proteins belong to a family of proteins called lipocalins, which share sequence homology with antigens of the parasitic agent that causes schistosomiasis. The fact that parasite infections also trigger IgE antibody responses may account for the development of LAA in persons who have never had any previous allergy. The prevention of LAA should be a major goal of an effective health and safety program in the animal research facility, and it can be accomplished by education and training of employees, reduction of exposure (including the use of personal protective gear), and changes in facility design. Medical surveillance programs can also play a role in improving health of individuals working with laboratory research animals. Early recognition of symptoms and evidence of sensitization can lead to interventions to reduce exposure and thereby avoid the long-term health consequences of LAA.

Upregulation of B7 molecules (CD80 and CD86) and exacerbated eosinophilic pulmonary inflammatory response in mice lacking the IFN-beta gene

BACKGROUND

IFN-beta has been shown to be effective as therapy for multiple sclerosis. Some reports attributed its beneficial effects to the capacity to induce a T(H)2 response. However, other studies have suggested that endogenous type I IFN might downregulate the allergic response in mice.

OBJECTIVE

We sought to define the differential role of endogenous IFN-beta in controlling the development of allergic inflammation.

METHODS

We assessed whether deletion of the gene encoding IFN-beta (IFNB) with knockout mice participated in the development of allergic response in ovalbumin (OVA)-sensitized and OVA-challenged mice.

RESULTS

OVA-sensitized and OVA-challenged mice with lack of the IFNB gene had more severe pulmonary inflammation with increased lung local response, including IL-4, IL-5, IL-13, IgE, eosinophilia, and goblet cells, than their litter mates (IFN-beta+/-), whereas no differences were observed in regard to local levels of IFN-gamma. Moreover, systemic response with IgE production is also enhanced. Lack of IFN-beta also results in significantly higher antigen-specific T cells, with higher levels of IL-4, IL-5, and IL-13, whereas no significant differences in IFN-gamma response could be observed. We have also detected a higher ratio of CD4+/CD8+ T cells and increased expression of B7.1/B7.2 on B cells and antigen-presenting cells in IFNB knockout mice.

CONCLUSIONS

These results demonstrate that IFN-beta plays an important role in immunoregulation of allergic response in mice. The stronger pulmonary inflammation could be a consequence of significantly expanded antigen-specific CD4+ T(H)2 cells as a result of efficient antigen presentation by antigen-presenting cells and hence increased production of IgE by B cells.

CD28 costimulation is critical for experimental allergic asthma in HLA-DQ8 transgenic mice

The objective of this study was to investigate the contribution of the CD28 costimulatory molecules to allergen-induced primary and chronic inflammatory responses. To this end, we have developed and characterized a short ragweed allergen-induced asthma model involving sensitization of HLA-DQ transgenic mice followed by intranasal challenge with allergen. Forty-eight hours after primary challenge, sensitized DQ8 mice developed pulmonary eosinophilic inflammation, airway hyperreactivity, Th2 cytokines, and IgE/IgG1 Ab. This allergic inflammatory response was absent in H-2Abeta(0) and DQ8/CD28(0) mice. Secondary rechallenge with allergen 4 weeks later induced even greater inflammatory changes in the airways of DQ8 mice with eosinophils being the predominant inflammatory cells while only pulmonary lymphocytosis was observed in DQ8/CD28(0) mice. No inflammation was detected in H-2Abeta(0) mice. Proliferation and cytokine profile studies demonstrated that CD28 regulates T-cell activation and effector function. Therefore, CD28 is essential for the extrinsic asthma and can be a target for immunotherapy.

Enhanced expression of B7.2 (CD86) by percutaneous sensitization with house dust mite antigen

House dust mite antigen is a well-known allergen in the pathogenesis of atopic dermatitis (AD), a chronic relapsing inflammatory skin disease. We evaluated the AD model mice sensitized with house dust mite antigen and observed a Th2-dominant immune response. In this experiment, BALB/c mice were sensitized percutaneously with house dust mite antigen three times with 7 days interval after skin barrier disruption. A remarkable infiltration of polymorphonuclear granulocytes and monocytes in the cutis was observed in mice treated with this antigen, high serum IgE levels and IL-4 mRNA expression in local lymph node cells was also observed. CD19(+) B cell numbers overturned to CD4(+) helper T cells. In these mice, there was significant increase of B7.2 (CD86) expression on CD19(+) B cells. These results indicate that house dust mite antigen sensitizes BALB/c mice and skews their Th1/Th2 balance toward Th2.

Dissociation by steroids of eosinophilic inflammation from airway hyperresponsiveness in murine airways

BACKGROUND

The link between eosinophils and the development of airway hyperresponsiveness (AHR) in asthma is still controversial. This question was assessed in a murine model of asthma in which we performed a dose ranging study to establish whether the dose of steroid needed to inhibit the eosinophil infiltration correlated with that needed to block AHR.

METHODS

The sensitised BALB/c mice were dosed with vehicle or dexamethasone (0.01-3 mg/kg) 2 hours before and 6 hours after each challenge (once daily for 6 days) and 2 hours before AHR determination by whole-body plethysmography. At 30 minutes after the AHR to aerosolised methacholine the mice were lavaged and differential white cell counts were determined. Challenging with antigen caused a significant increase in eosinophils in the bronchoalveolar lavage (BAL) fluid and lung tissue, and increased AHR.

RESULTS

Dexamethasone reduced BAL and lung tissue eosinophilia (ED50 values of 0.06 and 0.08 mg/kg, respectively), whereas a higher dose was needed to block AHR (ED50 of 0.32 mg/kg at 3 mg/ml methacholine. Dissociation was observed between the dose of steroid needed to affect AHR in comparison with eosinophilia and suggests that AHR is not a direct consequence of eosinophilia.

CONCLUSION

This novel pharmacological approach has revealed a clear dissociation between eosinophilia and AHR by using steroids that are the mainstay of asthma therapy. These data suggest that eosinophilia is not associated with AHR and questions the rationale that many pharmaceutical companies are adopting in developing low-molecular-mass compounds that target eosinophil activation/recruitment for the treatment of asthma.

Chronic exposure to innocuous antigen in sensitized mice leads to suppressed airway eosinophilia that is reversed by granulocyte macrophage colony-stimulating factor

In this study we investigated the impact of chronic allergen exposure on airway inflammation and humoral responses in sensitized mice. We observed marked eosinophilia in the bronchoalveolar lavage, lung tissue, and peripheral blood after 2 wk of exposure. In contrast, eosinophilia was markedly reduced by 3 wk and completely resolved by 4 wk of exposure, despite the continued presence of Ag. Decreases in airway eosinophilia were associated with a robust humoral response. We observed that levels of OVA-specific IgE, IgG1, and IgG2a increased during the course of exposure. To assess whether continuous exposure to Ag impacts the ability of the lung to respond to subsequent Ag challenge, mice were exposed to either 2 or 4 wk of OVA in the context of GM-CSF. All groups were then rested for 28 days and exposed to OVA on three consecutive days. We observed a significant decrease in airway eosinophilia and IL-5 expression in the bronchoalveolar lavage and serum in mice initially exposed to 4 wk of OVA, compared with animals exposed to 2 wk only. However, in both groups expression of B7.2 on dendritic cells as well as CD25, CD69, and T1/ST2 on CD4(+) T cells was enhanced, suggesting immune activation. Delivery of rGM-CSF fully restored airway eosinophilia. This study shows that exposure to innocuous Ag alone does not lead to persistent eosinophilic airway inflammation, but rather to abrogated eosinophilia. This suppression can be reversed by GM-CSF.

Differential stimulation of IgE production, STAT activation and cytokine and CD86 expression by 2,4-dinitrochlorobenzene and trimellitic anhydride

It has been reported that dermal exposure to trimellitic anhydride (TMA, 50%), a respiratory allergen, induced greater production of serum IgE and expression of Th2 cytokines than 2,4-dinitrochlorobenzene (DNCB, 1%), a potent contact sensitizer, in female BALB/C mice. To determine if there is any strain difference, four strains (B6C3F1, C57BL/6, BDF1 and BALB/C) of female mice were employed in this study to compare the differential effects of these chemicals on the hypersensitivity responses. Serum IgE levels were increased in TMA-treated B6C3F1, C57BL/6 and BDF1 mice when compared with the DNCB treatment and vehicle controls; in contrast, no difference was observed between TMA- and DNCB-treated BALB/C mice, although both chemicals induced greater IgE production than vehicle controls. In vitro expression of interleukin 4 (IL-4) and IL-13 mRNA by overnight concanavalin A (ConA)-stimulated draining lymph node cells was enhanced following in vivo treatment with TMA but not with DNCB in the B6C3F1, C57BL/6 and BDF1 mice. In contrast, TMA and DNCB induced similar levels of IL-4 and IL-13 mRNA in the BALB/C mice. The IL-4 protein levels in the supernatants of overnight ConA-treated draining lymph node cells were also increased in TMA-treated B6C3F1 and C57BL/6 mice when compared with the DNCB treatment and vehicle controls. Further mechanistic evaluation in the B6C3F1 mice indicated that the activation of STAT6 but not STAT4 by ConA plus IL-2-treated draining lymph node cells was increased in TMA- but not DNCB-treated mice when compared with the vehicle controls. Furthermore, surface expression of B7.2 (CD86) by B cells was increased in both TMA- and DNCB-treated B6C3F1 mice when compared with the vehicles; however, greater B7.2 expression was observed in TMA-treated compared with DNCB-treated. Overall, these results demonstrate that a similar pattern of IgE and cytokine production was observed in these strains of mice except for BALB/C. Furthermore, differential activation of STAT6 and expression of CD86 following exposure to TMA and DNCB may contribute to the differential production of IgE and cytokines.

The use of anti-IgE in the treatment of allergic asthma

Allergic sensitization plays a significant role in the development of asthma in many patients. IgE-mediated immune responses play a central role in the pathogenesis of this condition. The development of a treatment that interrupts this pathway is particularly desirable to prevent downstream events. Large-scale trials in patients ranging in age from 6 to 76 years have shown that omalizumab therapy is safe and effective in the treatment of severe allergic asthma. This is particularly true in patients who experience poor disease control despite high doses of inhaled steroids or need oral steroids for control of their disease. These patients are at risk for severe exacerbations despite recommended therapy, and anti-IgE therapy has proved to reduce these episodes. Early aggressive therapy of asthma is needed for maximum control in all age groups. Despite the efficacy of inhaled steroids there is a reluctance to use these agents, especially in younger children. Because of these concerns a long-acting treatment is especially desirable. Because of imperfect effort or technique limiting inhaled medications, introduction of an effective agent that could be administered parenterally at long intervals also is very important. Allergic rhinitis is a co-existing problem in many patients with allergic asthma. Immunotherapy trials have suggested that early intervention with immunotherapy and allergic rhinitis patients may actually prevent the development of asthma. Early treatment of patients with anti-IgE may also have benefits, particularly in those who have concomitant allergic rhinitis in addition to allergic asthma. Although omalizumab has not yet received Food and Drug Administration approval in the United States, it shows great promise in the management of patients requiring high doses of inhaled or oral corticosteroids for control of their disease and to prevent exacerbations of asthma in such patients. Reductions in high doses of inhaled or oral corticosteroids may prevent long-term complications of these treatments.

CD4 T-helper cells engineered to produce IL-10 prevent allergen-induced airway hyperreactivity and inflammation

BACKGROUND

T(H)2 cells play a critical role in the pathogenesis of asthma, but the precise immunologic mechanisms that inhibit T(H)2 cell function in vivo are not well understood.

OBJECTIVE

The purpose of our studies was to determine whether T cells producing IL-10 regulate the development of asthma.

METHODS

We used gene therapy to generate ovalbumin-specific CD4 T-helper cells to express IL-10, and we examined their capacity to regulate allergen-induced airway hyperreactivity.

RESULTS

We demonstrated that the CD4 T-helper cells engineered to express IL-10 abolished airway hyperreactivity and airway eosinophilia in BALB/c mice sensitized and challenged with ovalbumin and in SCID mice reconstituted with ovalbumin-specific T(H)2 effector cells. The inhibitory effect of the IL-10-secreting T-helper cells was accompanied by the presence of increased quantities of IL-10 in the bronchoalveolar lavage fluid, was antigen-specific, and was reversed by neutralization of IL-10. Moreover, neutralization of IL-10 by administration of anti-IL-10 mAb in mice sensitized and challenged with ovalbumin seriously exacerbated airway hyperreactivity and airway inflammation.

CONCLUSION

Our results demonstrate that T cells secreting IL-10 in the respiratory mucosa can indeed regulate T(H)2-induced airway hyperreactivity and inflammation, and they strongly suggest that IL-10 plays an important inhibitory role in allergic asthma.

Inhibitory action of a macrolide antibiotic, roxithromycin, on co-stimulatory molecule expressions in vitro and in vivo

OBJECTIVE

The influence of a macrolide antibiotic, roxithromycin (RXM), on co-stimulatory molecule expression was examined in vitro and in vivo.

MATERIALS AND METHODS

Spleen cells obtained from BALB/c mice 10 days after immunization with 8.0 microg of hemocyanin absorbed to 4.0 mg of aluminum hydroxide were cultured in the presence of 100.0 microg/ml of hemocyanin and various concentrations of RXM. We first examined the influence of RXM on cell activation by examining the proliferative response of cells and cytokine production. We also examined the influence of RXM on co-stimulatory molecule (CD40, CD80 and CD86) expressions on cultured splenic B-lymphocytes induced by in vitro antigenic stimulation using flow cytometry. In the second part of experiments, non-immunized and immunized mice were treated orally with 2.5 mg/kg of RXM once a day for 4 or 8 weeks. Splenic B lymphocytes were obtained from these mice 24 h after antigenic challenge, and co-stimulatory molecule expressions were examined by flow cytometer.

RESULTS

Cell activation induced by in vitro antigenic stimulation was suppressed by RXM when cells were cultured in the presence of more than 5.0 microg/ml of the agent. Addition of RXM at a concentration of 5.0 microg/ml into cell cultures also suppressed co-stimulatory molecule (CD40, CD80 and CD86) expressions on splenic B lymphocytes, which was enhanced by antigenic stimulation in vitro. Oral RXM administration for 4 weeks clearly suppressed the enhancement of CD40 and CD86 (but not CD80) expressions on splenic B lymphocytes induced by antigenic stimulation in vivo. This suppressive activity of RXM on co-stimulatory molecule (CD40 and CD86) expressions was further strengthened by the treatment of mice for 8 weeks. Long-term treatment with oral RXM also suppressed CD80 expressions, which was not suppressed by 4-week treatment.

CONCLUSION

The present results suggest that RXM exerts its immunomodulating effects through suppression of both cell activation and co-stimulatory molecule expressions induced by antigenic stimulation. These suppressive activities of RXM might contribute, in part, to the therapeutic mode of action of RXM on inflammatory diseases.

Chronic helminth infection induces alternatively activated macrophages expressing high levels of CCR5 with low interleukin-12 production and Th2-biasing ability

Helminth infections induce Th2-type biased immune responses. Although the mechanisms involved in this phenomenon are not yet clearly defined, antigen-presenting cells (APC) could play an important role in this process. Here, we have used peritoneal macrophages (F4/80+) recruited at different times after challenge with Taenia crassiceps as APC and tested their ability to regulate Th1/Th2 differentiation. Macrophages from acute infections produced high levels of interleukin-12 (IL-12) and nitric oxide (NO), paralleled with low levels of IL-6 and prostaglandin E(2) (PGE(2)) and with the ability to induce strong antigen-specific CD4+ T-cell proliferation in response to nonrelated antigens. In contrast, macrophages from chronic infections produced higher levels of IL-6 and PGE(2) and had suppressed production of IL-12 and NO, associated with a poor ability to induce antigen-specific proliferation in CD4+ T cells. Failure to induce proliferation was not due to a deficient expression of accessory molecules, since major histocompatibility complex class II, CD40, and B7-2 were up-regulated, together with CD23 and CCR5 as infection progressed. These macrophages from chronic infections were able to bias CD4+ T cells to produce IL-4 but not gamma interferon (IFN-gamma), contrary to macrophages from acute infections. Blockade of B7-2 and IL-6 and inhibition of PGE(2) failed to restore the proliferative response in CD4+ T cells. Furthermore, studies using STAT6(-/-) mice revealed that STAT6-mediated signaling was essential for the expansion of these alternatively activated macrophages. These data demonstrate that helminth infections can induce different macrophage populations that have Th2-biasing properties.

Association of asthma severity and bronchial hyperresponsiveness with a polymorphism in the cytotoxic T-lymphocyte antigen-4 gene

OBJECTIVES

Cytotoxic T-lymphocyte antigen (CTLA)-4 is a homolog of CD28, which is expressed only on activated T cells. It binds to accessory molecule B7 and mediates T-cell-dependent immune response. Signaling through CTLA-4 may down-regulate type 1 T-helper cell proliferation; moreover, some studies suggest that CTLA-4 might also deliver a positive signal to type 2 T-helper cell activation. Disruption of this delicate balance of immune regulation may lead to autoimmune diseases or atopic diseases. To evaluate the possible role of CTLA-4 polymorphisms in bronchial asthma, we investigated the association between polymorphisms (exon 1 +49 A/G, promoter -318 C/T) and atopy, asthma severity, and bronchial hyperresponsiveness in bronchial asthma patients and a group of healthy control subjects.

PATIENTS

Eighty-eight asthmatic patients and 88 healthy control subjects were studied.

MEASUREMENTS AND RESULTS

Asthma severity assessment, methacholine challenge, allergy skinprick test, and serum total IgE measurements were performed. The genotypes of the CTLA-4 promoter (-318 C/T) and exon 1 (+49 A/G) in all subjects were determined using the polymerase chain reaction and restriction fragment length polymorphism. The CTLA-4 promoter (-318 C/T) polymorphism was shown to be associated with asthma severity, but not with asthma, atopy, or bronchial hyperresponsiveness. A significant association was found between severe asthma and the T allele (p = 0.037). The CTLA-4 exon 1 (+49 A/G) polymorphism was shown to be associated with bronchial hyperresponsiveness, but not with asthma, atopy, or asthma severity. Asthmatic patients of the GG genotype had more hyperresponsive airways than those with the AG or AA genotype (p = 0.019).

CONCLUSIONS

The CTLA-4 promoter (-318 C/T) T allele may serve as a clinically useful marker of severe asthma. The CTLA-4 exon 1 (+49 A/G) polymorphism may have a disease-modifying effect in asthmatic airways.

Role of cytokines and chemokines in bronchial hyperresponsiveness and airway inflammation

Over the last decade there has been an intense interest in the potential role of cytokines and chemokines as important mediators in various atopic diseases, including asthma and the mechanisms by which these mediators regulate airway inflammation and bronchial hyperresponsiveness. This research effort has recently culminated in the publication of clinical studies that have assessed the role of interleukin (IL)-4 [Borish et al., Am J Respir Crit Care Med 160, 1816-1823 (1999)], IL-5 [Leckie et al., Lancet 356, 2144-2148 (2000)], and IL-12 [Bryan et al., Lancet 356, 2149-2153 (2000)] in allergic asthma, and the results have been disappointing. This is not surprising given the pleiotropic role cytokines play in the allergic response confirmed by numerous animal studies providing evidence of functional redundancy. The alternative view is that our current concepts in asthma pathogenesis need significant revision. This review will summarise the evidence for the role of cytokines and chemokines in various aspects of asthma pathophysiology; namely, bronchial hyperresponsiveness, eosinophil recruitment to the airways, mucus secretion, and airway remodelling.

Toll-like receptor 4 is required for optimal development of Th2 immune responses: role of dendritic cells

LPS potently induces dendritic cell maturation and the production of proinflammatory cytokines, such as IL-12, by activation of Toll-like receptor 4 (TLR4). Since IL-12 is important for the generation and maintenance of Th1 responses and may also inhibit Th2 cell generation from naive CD4 T cell precursors, it has been inferred that TLR4 signaling would have similar effects via the induction of IL-12 secretion. Surprisingly, we found that TLR4-defective mice subjected to sensitization and pulmonary challenge with a protein allergen had reductions in airway inflammation with eosinophils, allergen-specific IgE levels, and Th2 cytokine production, compared with wild-type mice. These reduced responses were attributable, at least in part, to decreased dendritic cell function: Dendritic cells from TLR4-defective mice expressed lower levels of CD86, a costimulatory molecule important for Th2 responses. They also induced less Th2 cytokine production by antigenically naive CD4 T cells in vitro and mediated diminished CD4 T cell Ag-specific pulmonary inflammation in vivo. These results indicate that TLR4 is required for optimal Th2 responses to Ags from nonpathogenic sources and suggest a role for TLR4 ligands, such as LPS derived from commensal bacteria or endogenously derived ligands, in maturation of the innate immune system before pathogen exposure.

Distribution of intranasal instillations in mice: effects of volume, time, body position, and anesthesia

Intranasal instillation techniques are used to deliver various substances to the upper and lower respiratory tract (URT and LRT) in mice. Here, we quantify the relative distribution achieved with intranasal delivery of a nonabsorbable tracer, (99m)Tc-labeled sulfide-colloid. Relative distribution was determined by killing mice after instillation and quantifying the radioactivity in dissected tissues using gamma scintigraphy. A significant effect of delivery volume on relative distribution was observed when animals were killed 5 min after instillation delivered under gas anesthesia. With a delivery volume of 5 microl, no radiation was detected in the LRT; this increased to a maximum of 55.7 +/- 2.5% distribution to the LRT when 50 microl were delivered. The majority of radiation not detected in the LRT was found in the URT. Over the course of the following 1 h, radiation in the LRT remained constant, while that in the URT decreased and appeared in the gastrointestinal tract. Instillation of 25 microl into anesthetized mice resulted in 30.1 +/- 6.9% distribution to the LRT, while only 5.3 +/- 1.5% (P < 0.05) of the same volume was detected in the LRT of awake mice. Varying the body position of mice did not affect relative distribution. When using intranasal instillation, the relative distribution between the URT and LRT and the gastrointestinal tract is heavily influenced by delivery volume and level of anesthesia.

Blockade of CD28/B7-2 costimulation inhibits experimental obliterative bronchiolitis in rat tracheal allografts: suppression of helper T cell type1-dominated immune response

T cell activation is a proximal event in the initiation of chronic rejection that may ultimately lead to obliterative bronchiolitis (OB) after lung transplantation. In addition to primary signals generated by the T cell receptor, T cell activation relies on costimulatory signals, of which the most important are mediated via interaction between CD28 and its ligands B7-1 and B7-2. In nontreated rat tracheal allografts, B7-2, but not B7-1, expression peaked 10 d after transplantation, unlike in syngeneic grafts, where no B7-2 upregulation was observed. Selective blockade of the CD28/B7-1 T cell costimulatory pathway by a mutant form of CTLA4Ig (cytotoxic T lymphocyte antigen 4 immunoglobulin), CTLA4IgY100F, did not affect epithelial injury or degree of luminal occlusion in rat tracheal allografts. Treatment with CTLA4Ig fusion protein, which blocks both CD28/B7-1 and CD28/B7-2 interaction, significantly delayed the development of epithelial injury and airway occlusion. Immunohistochemical analyses of allografts showed that selective inhibition of the CD28/B7-1 pathway did not affect cytokine expression. In contrast, treatment with CTLA4Ig was associated with a significant decrease in the intragraft production of tumor necrosis factor alpha, interleukin 2, and interferon gamma, as well as slightly increased intragraft expression of interleukin 10. In conclusion, CTLA4Ig-mediated costimulatory blockade delays epithelial injury and attenuates obliterative changes and is associated with marked suppression of helper T cell type 1 (Th1)-dominated cytokine response. These observations emphasize the role of the CD28/B7-2 costimulatory pathway in regulating proinflammatory and Th1 cytokine responses and thereby in the development of epithelial and graft injury gradually leading to obliteration of the airway lumen.

Inhalation of a harmless antigen (ovalbumin) elicits immune activation but divergent immunoglobulin and cytokine activities in mice

BACKGROUND

Exposure to aerosolized harmless antigen such as ovalbumin (OVA) has previously been shown to induce inhalation tolerance, a state characterized by inhibition of IgE synthesis and airway inflammation, upon secondary immunogenic antigen encounter. Immune events associated with this phenomenon are still poorly understood.

OBJECTIVE

The aim of this study was to investigate cellular and molecular mechanisms underlying this state of 'unresponsiveness'.

METHODS

After initial repeated OVA exposure, mice were subjected to a protocol of antigen-induced airway inflammation, encompassing two intraperitoneal injections of OVA adsorbed to aluminium hydroxide followed by airway challenge. We assessed immune events in the draining lymph nodes after sensitization, and in the lungs after challenge.

RESULTS

In animals initially exposed to OVA, we observed, at the time of sensitization, considerable expansion of T cells, many of which expressed the activation markers CD69 and CD25, as well as increased numbers of antigen-presenting cells, particularly B cells. While these animals produced low levels of IgE, the observed elevated levels of IgG1 signified isotype switching. Splenocytes and lymph node cells from OVA-exposed mice produced low levels of IL-4, IL-5, IL-13 and IFN-gamma, indicating aborted effector function of both T helper (Th)2- and Th1-associated cytokines. Real time quantitative polymerase chain reaction (PCR) (TaqMan) analysis of costimulatory molecules in the lungs after in vivo challenge showed that B7.1, B7.2, CD28 and CTLA-4 mRNA expression was low in animals initially exposed to OVA. Ultimately, these events were associated with abrogated airway inflammation and attenuated airway hyper-responsiveness. The decreased inflammation was antigen-specific and independent of IL-10 or IFN-gamma.

CONCLUSION

Initial exposure to OVA establishes a programme that prevents the generation of intact, fully functional inflammatory responses upon secondary antigen encounter. The absence of inflammation, however, is not associated with categorical immune unresponsiveness.

T cell vaccination eliminates antigen-specific T cells and prevents antigen-induced eosinophil recruitment into the tissue

Asthma is characterized by airway inflammation with prominent eosinophil infiltrates. In a murine model of asthma, antigen-induced eosinophil recruitment into the airways of sensitized mice is mediated by CD4+ T cells and their cytokines, especially IL-5. In the present study, using ovalbumin-specific T cell receptor transgenic mice, we found that T cell vaccination, which was the administration of preactivated and attenuated antigen-specific T cells by the intraperitoneal route, prevented antigen-induced eosinophil recruitment into the airways. This effect was antigen-specific because ovalbumin-specific T cell vaccination did not affect BSA-induced eosinophil recruitment into the airways. We also found that antigen-specific IgE production as well as antigen-induced proliferation and cytokine production of splenocytes were diminished by T cell vaccination. Moreover, flow-cytometric analyses revealed that T cell vaccination eliminated antigen-specific T cells in the periphery. Together, these results indicate that T cell vaccination prevents antigen-induced eosinophil recruitment into the airways presumably by eliminating antigen-specific T cells.

Suppressive effects of anti-allergic agent suplatast tosilate (IPD-1151T) on the expression of co-stimulatory molecules on mouse splenocytes in vivo

The effects of IPD-1151T on the expression of co-stimulatory molecules, CD40, CD80 and CD86, were investigated in vivo using mice with allergic disorders. BALB/c mice were immunized intraperitoneally with two doses of dinitrophenylated ovalbumin (DNP-OVA) at 1-week intervals. These mice then were treated intraperitoneally with 100 microg/kg of IPD-1151T once a day for 14 days, starting 7 days after the first immunization. On day 21, some mice were challenged intraperitoneally with DNP-OVA and the other mice were not challenged. All mice were autopsied on day 22 and assayed for immunoglobulin E, interleuken (IL)-4 and IL-5 productions following DNP-OVA immunization. The intraperitoneal treatment with IPD-1151T strongly suppressed immunoglobulin E contents in serum, which were enhanced by DNA-OVA immunization. IPD-1151T also caused a decrease in both IL-4 and IL-5 levels in splenic lymphocytes. We next examined the influence of IPD-1151T on co-stimulatory molecule expression on splenic lymphocytes. IPD-1151T caused suppression of CD40 and CD86 expression; however, the treatments did not affect CD80 expression.

CTLA4-IgG reverses asthma manifestations in a mild but not in a more "severe" ongoing murine model

We investigated whether CTLA4-Ig can reverse established asthma manifestations in a novel murine model of ongoing disease. In BALB/c mice, sensitized to ovalbumin (OVA) without adjuvant, airway inflammation was induced by a first series of OVA aerosol challenges. Murine CTLA4-IgG was then administered, followed by a second series of OVA inhalations. In control-treated mice, two series of OVA challenges induced upregulation of OVA-specific IgE in serum, eosinophils in the bronchoalveolar lavage fluid (BALF), and IL-5 production by lung lymphocytes upon OVA restimulation in vitro, compared with saline-challenged mice. CTLA4-IgG significantly inhibited all of these parameters in OVA-challenged mice. Importantly, mCTLA4-IgG performed better than the gold-standard dexamethasone because this corticosteroid did not inhibit the upregulation of OVA-specific IgE in serum. In a more "severe" ongoing model, induced by sensitization to OVA emulsified in aluminum hydroxide, resulting in airway hyperresponsiveness to methacholine and stronger inflammatory responses, mCTLA4-IgG was less effective in that only the number of eosinophils in the BALF was reduced (P = 0.053), whereas dexamethasone inhibited both BALF eosinophilia and cytokine production by lung lymphocytes. Thus, CTLA4-Ig might be an effective alternative therapy in established allergic asthma, especially in situations of mild disease.

Differential role of CD80 and CD86 molecules in the induction and the effector phases of allergic rhinitis in mice

Selective involvement of CD80 and/or CD86 in the differentiation of T-helper (Th)1 and Th2 was seen in several diseases. In this study, we sought to determine the differential roles of CD80 and CD86 in the induction and effector phase of allergic rhinitis using Schistosoma mansoni egg antigen (SEA) as a specific Ag. Intranasal sensitization with SEA in BALB/c mice elicited a strong Th2 response including SEA-specific IgE production, nasal eosinophilia, and IL-4 and IL-5 production by nasal lymphocytes after Ag challenge. Blockade of CD80 at the induction phase significantly inhibited these manifestations, whereas no effect was observed by CD86 blockade. In contrast, the simultaneous blockade of both CD80 and CD86 during the effector phase partially inhibited IgE and IgG(1) production and nasal eosinophilia, although either blockade of CD80 or CD86 during the phase failed to inhibit these responses. Flow cytometric analysis on nasal mononuclear cells showed that CD80 but not CD86 was preferentially expressed on non-B cells by in vitro SEA stimulation in unsensitized mice. However, both CD80 and CD86 expression were significantly augmented by in vitro SEA stimulation in sensitized mice. Our results suggest the differential roles and expression of CD80 and CD86 in the development of allergic rhinitis.