Induce Th2 Cytokine Production Research Articles

IL-18 and infections: Is there a role for targeted therapies?

Interleukin (IL)-18 is a pro-inflammatory cytokine belonging to the IL-1 family, first identified for its interferon-γ-inducing properties. IL-18 regulates both T helper (Th) 1 and Th2 responses. It acts synergistically with IL-12 in the Th1 paradigm, whereas with IL-2 and without IL-12 it can induce Th2 cytokine production from cluster of differentation (CD)4+ T cells, natural killer (NK cells, NKT cells, as well as from Th1 cells. IL-18 also plays a role in the hemophagocytic lymphohistiocytosis, a life-threatening condition characterized by a cytokine storm that can be secondary to infections. IL-18-mediated inflammation was largely studied in animal models of bacterial, viral, parasitic, and fungal infections. These studies highlight the contribution of either IL-18 overproduction by the host or overresponsiveness of the host to IL-18 causing an exaggerated inflammatory burden and leading to tissue injury. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19). The damage in the later phase of the disease appears to be driven by a cytokine storm, including interleukin IL-1 family members and secondary cytokines like IL-6. IL-18 may participate in this hyperinflammation, as it was previously found to be able to cause injury in the lung tissue of infected animals. IL-18 blockade has become an appealing therapeutic target and has been tested in some IL-18-mediated rheumatic diseases and infantile-onset macrophage activation syndrome. Given its role in regulating the immune response to infections, IL-18 blockade might represent a therapeutic option for COVID-19, although further studies are warranted to investigate more in detail the exact role of IL-18 in SARS-CoV-2 infection.

IL-25 enhances TH17 cell–mediated contact dermatitis by promoting IL-1β production by dermal dendritic cells

In addition to thymic stromal lymphopoietin and IL-33, IL-25 is known to induce TH2 cytokine production by various cell types, including TH2 cells, TH9 cells, invariant natural killer T cells, and group 2 innate lymphoid cells, involved in TH2-type immune responses. Because both TH2-type and TH17-type cells/cytokines are crucial for contact hypersensitivity (CHS), IL-25 can contribute to this by enhancing TH2-type immune responses. However, the precise role of IL-25 in the pathogenesis of fluorescein isothiocyanate-induced CHS is poorly understood. We investigated the contribution of IL-25 to CHS using Il25-/- mice. CHS was evaluated by means of measurement of ear skin thickness in mice after fluorescein isothiocyanate painting. Skin dendritic cell (DC) migration, hapten-specific TH cell differentiation, and detection of IL-1β-producing cells were determined by using flow cytometry, ELISA, and immunohistochemistry, respectively. In contrast to thymic stromal lymphopoietin, we found that IL-25 was not essential for skin DC migration or hapten-specific TH cell differentiation in the sensitization phase of CHS. Unexpectedly, mast cell- and non-immune cell-derived IL-25 was important for hapten-specific TH17 cell-mediated rather than TH2 cell-mediated inflammation in the elicitation phase of CHS by enhancing TH17-related, but not TH2-related, cytokines in the skin. In particular, IL-1β produced by dermal DCs in response to IL-25 was crucial for hapten-specific TH17cell activation, contributing to induction of local inflammation in the elicitation phase of CHS. Our results identify a novel IL-25 inflammatory pathway involved in induction of TH17 cell-mediated, but not TH2 cell-mediated, CHS. IL-25 neutralization can be a potential approach for treatment of CHS.

Peanut T-cell epitope discovery: Ara h 1

Identification of potential T-cell epitopes in the peanut major allergens is essential for development of peptide-based immunotherapy. Traditional methods of T-cell epitope discovery use overlapping short peptides spanning the full length of the protein in T-cell proliferation assays. Because large proteins, such as Ara h 1, require a large number of peptides, this limits screening to a small number of allergic subject-derived T-cell lines. We sought to identify candidate peptides of Ara h 1 that display promiscuous binding to MHC class II and induce TH2 cytokine production by Tcells. In silico MHC class II binding prediction was performed with NetMHCIIpan 2.0 (peptide length, 15; 1-mer offset) and the most abundant class II alleles in the North American population and with an invitro MHC class II peptide reporter assay performed in parallel, which used synthetic 15-mer peptides offset by 5 mer spanning the protein. High-resolution MHC class II typing and a T-cell proliferation assay using preselected peptides were performed with PBMCs from 98 subjects with peanut allergy and 14 healthy control subjects. IL-4, IL-13, IL-5, IFN-γ, and TNF-α levels were measured in culture supernatants. Thirty-six Ara h 1 peptides were identified by using in silico predictions and MHC class II binding assays. In combination with T-cell proliferation and cytokines secreted in T-cell assays, we have identified 4 vaccine candidate Ara h 1 peptides. Preselection of peptides by using in silico and invitro approaches in combination with conventional methods appears to be an effective strategy for identifying peanut T-cell peptide vaccine candidates.

IL-33, but Not IL-25, Is Crucial for the Development of House Dust Mite Antigen-Induced Allergic Rhinitis

Both interleukin (IL)-33 and IL-25 induce Th2 cytokine production by various cell types, suggesting that they contribute to development of allergic disorders. However, the precise roles of IL-33 and IL-25 in house dust mite (HDM)-induced allergic rhinitis (AR) remain unclear. Both IL-33 and IL-25 were produced mainly by nasal epithelial cells during HDM-induced AR. Eosinophil and goblet cell counts in the nose and IL-5 levels in lymph node cell culture supernatants were significantly decreased in IL-33-deficient, but not IL-25-deficient, mice compared with wild-type mice during HDM-induced AR, but the serum IgE and IgG1 levels did not differ. On the other hand, HDM-induced AR developed similarly in wild-type mice transferred with either IL-33-deficient BM cells or wild-type BM cells. IL-33, but not IL-25, produced by nasal epithelial cells was crucial for the development of murine HDM-induced AR. These observations suggest that IL-33 neutralization may be a potential approach for treatment of HDM-induced AR in humans.

Retraction: Vα24-Invariant NKT Cells from Patients with Allergic Asthma Express CCR9 at High Frequency and Induce Th2 Bias of CD3+ T Cells upon CD226 Engagement

We have demonstrated that Valpha24(+)Vbeta11(+) invariant (Valpha24(+)i) NKT cells from patients with allergic asthma express CCR9 at high frequency. CCR9 ligand CCL25 induces chemotaxis of asthmatic Valpha24(+)i NKT cells but not the normal cells. A large number of CCR9-positive Valpha24(+)i NKT cells are found in asthmatic bronchi mucosa, where high levels of Th2 cytokines are detected. Asthmatic Valpha24(+)i NKT cells, themselves Th1 biased, induce CD3(+) T cells into an expression of Th2 cytokines (IL-4 and IL-13) in cell-cell contact manner in vitro. CD226 are overexpressed on asthmatic Valpha24(+)i NKT cells. CCL25/CCR9 ligation causes directly phosphorylation of CD226, indicating that CCL25/CCR9 signals can cross-talk with CD226 signals to activate Valpha24(+)i NKT cells. Prestimulation with immobilized CD226 mAb does not change ability of asthmatic Valpha24(+)i NKT cells to induce Th2-cytokine production, whereas soluble CD226 mAb or short hairpin RNA of CD226 inhibits Valpha24(+)i NKT cells to induce Th2-cytokine production by CD3(+) T cells, indicating that CD226 engagement is necessary for Valpha24(+)i NKT cells to induce Th2 bias of CD3(+) T cells. Our results are providing with direct evidence that aberration of CCR9 expression on asthmatic Valpha24(+)i NKT cells. CCL25 is first time shown promoting the recruitment of CCR9-expressing Valpha24(+)i NKT cells into the lung to promote other T cells to produce Th2 cytokines to establish and develop allergic asthma. Our findings provide evidence that abnormal asthmatic Valpha24(+)i NKT cells induce systemically and locally a Th2 bias in T cells that is at least partially critical for the pathogenesis of allergic asthma.

Role of IL-33 and Eosinophils in Intestinal Inflammation

IL-33, a recently identified cytokine, is linked to autoimmune and inflammatory diseases. Several studies define increased expression of IL-33 in the affected mucosa of patients with inflammatory bowel diseases (IBD). IL-33 can induce Th2 cytokine production and leukocyte mediator release. While eosinophils have been circumstantially associated with inflammatory bowel diseases (IBDs), very recent studies suggest IL-33 impacts eosinophil's function by increasing eosinophil adhesiveness to extracellular matrix and inducing inflammatory mediator release in IBD. The goal of this project is to identify mechanisms by which IL-33 impacts eosinophil function during intestinal inflammation in murine models of IBD. We hypothesize that IL-33 increases eosinophil degranulation and intestinal inflammation. Primary peripheral human blood eosinophils were isolated and assessed immediately or were cultured for 3 hours in the presence of IL-33 or other cytokines including IL-5, IL-1β, TNF-α or IFN-γ for flow cytometric assessment of the IL-33 cognate receptor ST2. Eosinophils were also assessed for the release of the eosinophil granule protein eosinophil peroxidase (EPO) and electron microscopic techniques. Alterations in cytokine expression were analyzed by real time RT-PCR. The impact of IL-33 on eosinophil migration was measured using an in vitro colonic epithelial (T84 cell) transwell-migration assay. In vivo analysis of IL-33 and eosinophils in mouse models of inflammatory bowel disease (IBD) employed the DSS colitis model in addition to the SAMP1/SkuSlc model of Th2 cytokine associated eosinophilic ileitis. Human tissue from IBD patients were assessed for eosinophilic inflammation and IL-33 by immunohistochemistry. The membrane bound IL-33 receptor, ST2, was present on freshly isolated human peripheral blood eosinophils. This level was further increased following incubation with IL-33 (100ng/ml) and IL-5 as well as the IBD associated IL-1β, TNF-α or IFN-γ cytokines (all 100ng/ml). IL-33 induced eosinophil degranulation as recorded by biochemical assay (>4-fold, p<0.05). In addition electron microscopic evidence demonstrated IL-33 induced eosinophil granule depletion. Stimulation of eosinophils with IL-33 led to production of IL-8 (>6-fold, p<0.01) and IL-13 (∽20-fold, p<0.001) compared to unstimulated cells. IL-33 induced increased eosinophil migration into the colonic epithelium (>3-fold). DSS colitis induced a robust increase in colonic eosinophils, ST2 transcript (>15-fold, p<0.01) as well as IL-33 mRNA (epithelial ∽30-fold, p<0.05 and whole tissue >6-fold, p<0.001). Similar findings were detected in another model of ileal involved IBD, SAMP1/SkuSlc mice. Following treatment of SAMP1/SkuSlc mice with anti-CCR3 antibody a significant decrease in ileal eosinophils (0.5-fold, p<0.001) and IL-33 was observed (0.25-fold, p<0.001). Eosinophilic inflammation and the cytokine IL-33 was increased in human IBD tissue specimens. Eosinophil activation by the pro-inflammatory cytokine IL-33 may contribute to eosinophil activation and intestinal inflammation.

IL-17E but not IL-17A is associated with allergic sensitization: results from the LISA study

Functional studies have provided evidence for the importance of IL-17A and IL-17E in the regulation of immune responses. IL-17A is involved in inflammation and IL-17E is able to induce Th2 cytokine production and eosinophilia. By now it is not clear whether these cytokines correlate with specific IgE levels. The aim of our investigation was to analyse the relationship of these two cytokines to allergic sensitization in context of an epidemiological study. Within the Life style Immune System Allergy study (LISA), we analysed phytohemagglutinin (PHA)-stimulated blood samples of 6 yr old children for the concentration of IL-17A and IL-17E and sera for levels of specific IgE. In total, data from 293 children were available for blood analysis and for the analysis of confounding factors for the allergic sensitization. Among the investigated children, 29% reacted against inhalant and 13.6% against food allergens, whereas 33.1% of children were sensitized to any allergen.IL-17E was associated with high levels of any specific IgE (adjusted odds ratio (OR) 1.45, 95% confidence interval (CI) 1.11–1.90). Furthermore, children with high IL-17E responses (>208.8 pg/ml) were sensitized to food and inhalant allergens (OR 1.45, 95% CI 1.02–2.07 and OR 1.35, 95% CI 1.03–1.77, respectively) and to Der p 1 (OR 1.55, 95% CI 1.12–2.15). In contrast, IL-17A, in trend, was negatively associated to sensitization to timothy (p for trend=0.013) and rye (p for trend=0.026). Concluding IL-17E production is linked to the amount of specific IgE antibodies in blood samples of 6 yr old children.

Identification of Candidate Proteins in Ragweed Extract (RWE) serves as alarmins that produce ROS and Induce Th2 Cytokine Production

Identification of Candidate Proteins in Ragweed Extract (RWE) serves as alarmins that produce ROS and Induce Th2 Cytokine Production

Elevated IL-6 expression in CD4 T cells via PKCθ and NF-κB induces Th2 cytokine production

T helper (Th) cell differentiation is a key event to mount an appropriate immune response. Th1 and Th2 cells produce their signature cytokines IFN-γ and IL-4, respectively. However, as we have reported, CD4 T cells selected by MHC class II-expressing thymocytes (T-CD4) produce both Th1 and Th2 type cytokines under Th1 differentiation conditions. Furthermore, the expression of Th2 cytokines in these cells is Stat6 independent. In the current study, we investigated the molecular mechanisms by which CD4 T cells produce Th2 cytokines under the Th1 differentiation condition. We observed that IL-6 is highly expressed in T-CD4 T cells, which is at least partly responsible for Th2 cytokine production by Th1 differentiated cells. The enhanced expression of IL-6 is downstream of constitutive phosphorylation of PKCθ and high NF-κB activity. Neutralizing IL-6, blocking PKCθ phosphorylation, or inhibiting NF-κB translocation diminished Th2 cytokine expression in Th1 cultures. Therefore, our study revealed that autocrine IL-6 production can induce Th2 cytokine production, and that PKCθ and NF-κB are essential components in the induction of IL-6-mediated Th2 development.

IL-19 Induced Th2 Cytokines and Was Up-regulated in Asthma Patients

Purpose of the Study. Interleukin-10 (IL-10) has been shown to inhibit allergen-induced airway hyperresponsiveness and inflammation. This study evaluates whether IL-19, a member of the IL-10 family, is associated with asthma. Study Population. The authors investigated IL-19 levels in 100 asthmatic patients, aged 3 to 12 years, as well as 50 healthy adults and 50 age-matched children. A dust mite–induced mouse model of asthma was also used to study the association of IL-19 with asthma. Methods. Cytokine levels were quantified by enzyme-linked immunosorbent assay. IL-19 levels were measured in all study subjects, but among asthmatic patients, the levels of IL-4 and IL-13 were analyzed in the 27 patients with the highest and 25 patients with the lowest IL-19 levels. By using a dust mite–sensitized murine asthma model, IL-19 levels were measured in asthmatic and control mice. To test whether IL-19 upregulates T-helper 2 (Th2) cytokines, IL-19 complementary DNA was injected into healthy mice using intramuscular electroporation, and serum levels of IL-4, IL-5, IL-10, and IL-13 were later monitored. After injection of IL-19 into asthmatic mice, IL-13 and immunoglobulin E (IgE) levels were measured. To determine if IL-19 could induce Th2 cytokine production in vitro, IL-19 was incubated with CD4+ T cells and IL-4, IL-5, IL-10, and IL-13 levels were quantified in the cell-culture supernatant. Results. Among asthmatic patients, the serum level of IL-19 was twice that of healthy controls, and those with a high level of IL-19 also had high levels of IL-4 and IL-13. In the murine asthma model, asthmatic mice also had IL-19 levels twice that of healthy control mice. Injection of the IL-19 gene into healthy mice induced production of IL-4, IL-5, and IL-10 but not IL-13. IL-19 upregulated IL-13 in asthmatic mice and also upregulated IgE production. In vitro, IL-19 was associated with increased IL-4, IL-5, IL-10, and IL-13 production by activated cells. Conclusions. IL-19 upregulates production of Th2 cytokines in activated T cells and may be an important molecule in the pathogenesis of asthma. Reviewer Comments. The Th2 cytokines upregulated by IL-19 play crucial roles in the pathogenesis of asthma. IL-13 regulates airway hypersensitivity and mucus hypersecretion; IL-4 is critical for IgE antibody switching; and IL-5 plays a key role in eosinophil maturation. The findings from this study suggest that IL-19 is another potentially important molecule in asthma pathogenesis and may be responsible, at least in part, for upregulation of Th2 cytokines that are critical to the development of allergic disease.

Vα24-Invariant NKT Cells from Patients with Allergic Asthma Express CCR9 at High Frequency and Induce Th2 Bias of CD3+ T Cells upon CD226 Engagement

We have demonstrated that Valpha24(+)Vbeta11(+) invariant (Valpha24(+)i) NKT cells from patients with allergic asthma express CCR9 at high frequency. CCR9 ligand CCL25 induces chemotaxis of asthmatic Valpha24(+)i NKT cells but not the normal cells. A large number of CCR9-positive Valpha24(+)i NKT cells are found in asthmatic bronchi mucosa, where high levels of Th2 cytokines are detected. Asthmatic Valpha24(+)i NKT cells, themselves Th1 biased, induce CD3(+) T cells into an expression of Th2 cytokines (IL-4 and IL-13) in cell-cell contact manner in vitro. CD226 are overexpressed on asthmatic Valpha24(+)i NKT cells. CCL25/CCR9 ligation causes directly phosphorylation of CD226, indicating that CCL25/CCR9 signals can cross-talk with CD226 signals to activate Valpha24(+)i NKT cells. Prestimulation with immobilized CD226 mAb does not change ability of asthmatic Valpha24(+)i NKT cells to induce Th2-cytokine production, whereas soluble CD226 mAb or short hairpin RNA of CD226 inhibits Valpha24(+)i NKT cells to induce Th2-cytokine production by CD3(+) T cells, indicating that CD226 engagement is necessary for Valpha24(+)i NKT cells to induce Th2 bias of CD3(+) T cells. Our results are providing with direct evidence that aberration of CCR9 expression on asthmatic Valpha24(+)i NKT cells. CCL25 is first time shown promoting the recruitment of CCR9-expressing Valpha24(+)i NKT cells into the lung to promote other T cells to produce Th2 cytokines to establish and develop allergic asthma. Our findings provide evidence that abnormal asthmatic Valpha24(+)i NKT cells induce systemically and locally a Th2 bias in T cells that is at least partially critical for the pathogenesis of allergic asthma.

IL-18 together with anti-CD3 antibody induces human Th1 cells to produce Th1- and Th2-cytokines and IL-8.

Although IL-18 was initially regarded as a factor that enhances IFN-gamma production from Th1 cells, later studies revealed its potential to induce Th2 cytokine production from T cells, NK cells and basophils/mast cells. Very recently, we demonstrated that passively transferred memory phenotype Th1 cells induce airway inflammation and hyperresponsiveness in a host mouse by production of Th1-, Th2-cytokines, GM-CSF and chemokines, when the transferred cells are stimulated in the host mice with nasally administered Ag and IL-18. Moreover, IL-18 is suggested to contribute to asthma exacerbation in human patients. Therefore, it is important to determine whether human Th1 cells also have the potential to produce these soluble factors when stimulated with anti-CD3 and IL-18 in vitro. Here we demonstrated that only Th1 cells, but not Th2 cells, produce IFN-gamma, IL-13, GM-CSF and IL-8 after stimulation with anti-CD3 and IL-18. Furthermore, highly purified IFN-gamma-producing Th1 cells have the same potential. Thus, human Th1 cells may become very harmful cells, when stimulated with Ag and IL-18 in vivo, and produce IFN-gamma, IL-13, GM-CSF and IL-8, which in combination might induce severe inflammation such as airway inflammation.

Elevated interleukin-18 levels in bronchoalveolar lavage fluid of patients with eosinophilic pneumonia.

Interleukin (IL)-18 can induce Th2 cytokine production particularly in collaboration with IL-2. Accumulation of Th2 cells and increased levels of Th2 cytokines are found in bronchoalveolar lavage fluid (BALF) from patients with eosinophilic pneumonia (EP). To evaluate the role of IL-18 in the pathogenesis of EP, we measured the concentration of IL-2, IL-12, IL-18, and Th2 cytokines in BALF from patients with EP. The concentrations of interferon (IFN)-gamma, IL-2, IL-5, IL-10, IL-12, IL-13, and IL-18 in BALF were measured in patients with idiopathic acute eosinophilic pneumonia (AEP), with idiopathic chronic eosinophilic pneumonia (CEP), with sarcoidosis and healthy volunteers (HV). The BALF concentrations of Th2 cytokines, IL-5, IL-10, and IL-13, were higher in patients with EP than in sarcoidosis and control. The IL-2 level in BALF was higher in EP than in sarcoidosis and control. The IL-18 and IL-12 (p40 + p70) levels were higher in patients with EP than sarcoidosis, while the level of IL-12 (p70) was below the detection limit in patients with EP. There was a significant correlation between IL-2 level and both IL-5 and IL-13 in BALF of patients with EP. Our findings suggest that IL-18 may contribute to Th2 cytokine-dominant responses in patients with EP in collaboration with IL-2.

Elevated interleukin-18 levels in bronchoalveolar lavage fluid of patients with eosinophilic pneumonia

Rationale Interleukin (IL)-18 can induce Th2 cytokine production particularly in collaboration with IL-2. Accumulation of Th2 cells and increased levels of Th2 cytokines are found in bronchoalveolar lavage fluid (BALF) from patients with eosinophilic pneumonia (EP). To evaluate the role of IL-18 in the pathogenesis of EP, we measured the concentration of IL-2, IL-12, IL-18, and Th2 cytokines in BALF from patients with EP. Methods The concentrations of IL-2, IL-5, IL-10, IL-12, IL-13 and IL-18 in BALF were measured in patients with acute eosinophilic pneumonia (AEP), with chronic eosinophilic pneumonia (CEP), with sarcoidosis and healthy volunteers (HV). Results The BALF concentrations of Th2 cytokines, IL-5, IL-10 and IL-13, were higher in patients with EP than in sarcoidosis and control. IL-2 level in BALF was higher in EP than in sarcoidosis and control. IL-18 and IL-12 (p40+p70) levels were higher in patients with EP than sarcoidosis, while the level of IL-12 (p70) was below the detection limit in patients with EP. There was a significant correlation between IL-2 level and both IL-5 and IL-13 in BALF of patients with EP. Conclusions Our findings suggest that IL-18 may contribute to Th2 cytokine-dominant responses in patients with EP in collaboration with IL-2.

Suppression of collagen-induced arthritis by natural killer T cell activation with OCH, a sphingosine-truncated analog of alpha-galactosylceramide.

OCH, a synthetic analog of alpha-galactosylceramide with a truncated sphingosine chain, stimulates natural killer T (NKT) cells to produce predominantly Th2 cytokines. Thus, OCH may be a potential agent for the treatment of Th1-mediated autoimmune diseases. This study was designed to evaluate the protective effects of OCH on collagen-induced arthritis (CIA) in mice. Mice were immunized with type II collagen (CII) and injected intraperitoneally twice per week with OCH, before or after the onset of CIA. They were monitored to assess the effect of OCH treatment on the severity of disease. Anti-CII antibodies and cytokine production were measured by enzyme-linked immunosorbent assay. Expression of cytokine genes was determined by quantitative reverse transcriptase-polymerase chain reaction. OCH inhibited CIA in wild-type C57BL/6 (B6) mice but not in NKT-deficient mice. OCH suppressed CIA in SJL mice, which are prone to autoimmune diseases and have a deficiency in the number and function of NKT cells which is similar to that in patients with autoimmune diseases, even after disease has already developed. Disease protection conferred by OCH correlated with its ability to selectively induce Th2 cytokine production mediated by NKT cells and to promote collagen-specific Th2 responses. Neutralization of interleukin-4 (IL-4) or IL-10 with monoclonal antibodies abolished disease protection by OCH, indicating a critical role for these cytokines. Taken together, our findings suggest that OCH holds possibilities as a therapeutic agent for autoimmune diseases such as rheumatoid arthritis.

Production of interleukin-13 by human dendritic cells after stimulation with protein allergens is a key factor for induction of T helper 2 cytokines and is associated with activation of signal transducer and activator of transcription-6.

Dendritic cells (DC) are able to induce not only T helper 1 (Th1) but also Th2 immune responses after stimulation with allergens. While DC-derived interleukin (IL)-12 and IL-18 are the key factors for the induction of Th1 cells, early signals being involved in Th2 differentiation are less well characterized so far. To analyse such early signals we used an antigen-specific setting with CD4+ T cells from atopic donors stimulated in the presence of autologous mature DC, which were pulsed with different allergen doses. The addition of increasing amounts of allergen during DC maturation with tumour necrosis factor-alpha, IL-1beta and prostaglandin E2 resulted in enhanced secretion of IL-6 and IL-12 by DC followed by increased production of Th1 (interferon-gamma; IFN-gamma) as well as Th2 (IL-4, IL-5) cytokines by CD4+ T cells. The coculture of allergen-treated DC and CD4+ T cells also led to a dose-dependent expression of active signal transducer and activator of transcription-6 (STAT6), which was visible already after 1 hr. Additionally, rapid phosphorylation of STAT6 was seen in immature DC after stimulation with allergens but not with lipopolysaccharide or human serum albumin. STAT6 phosphorylation was associated with the production of IL-13 by DC. The addition of neutralizing anti-IL-13 antibodies during maturation of DC inhibited STAT6 phosphorylation in CD4+ T cells as well as the production of IL-4, and to a lesser extent of IL-5, while IFN-gamma production was not affected. Addition of exogenous IL-13 enhanced mainly the secretion of IL-4. Taken together, DC-derived IL-13, which is released after exposure to allergens appears to be one of the critical factors for DC to acquire the capability to induce Th2 cytokine production.

Lipoteichoic acid from Staphylococcus aureus induces Th2-prone dermatitis in mice sensitized percutaneously with an allergen.

We found previously that lipoteichoic acid (LTA) from Staphylococcus aureus has the ability to induce Th2 cytokine production by peripheral blood mononuclear cells (PBMC) from patients with atopic dermatitis (AD). However, it is not known whether LTA can induce a Th2-dominant cytokine response in the skin of AD patients. The purpose of this study was to determine the effects of LTA in mice sensitized percutaneously with a house dust mite antigen (MA) through barrier-disrupted skin, as an experimental animal model of AD. Mice were sensitized with MA by a single topical application to barrier-disrupted abdominal skin. Seven days after the sensitization, the mice were challenged on the dorsal skin by LTA to elicit localized skin inflammation. The cytokine response in the dorsal skin was investigated by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistological analysis. The infiltration of inflammatory cells in the skin was also observed by histological staining. Injection of LTA into the dorsal skin of MA-sensitized mice, which show a Th2-dominant cytokine response against the homologous antigen, increased the expression of mRNA for IFN-gamma, IL-4 and IL-5, but not IL-2. Immunohistological analysis demonstrated that levels of IFN-gamma, IL-4 and IL-5 transcripts corresponded with those of protein synthesis. In addition, the dorsal skin of MA-sensitized mice challenged with LTA showed significantly increased numbers of neutrophils, eosinophils, mononuclear cells and mast cells compared with control mice challenged with LTA. These results suggest that LTA has the ability to induce localized Th2-prone dermatitis in an allergen-independent manner in the skin of AD patients and may explain the role of colonization with S. aureus in AD patients.

257 Diesel exhaust particles and ragweed allergen in vivo induce TH2 cytokine production in the nasal mucosa of ragweed-sensitive subjects

257 Diesel exhaust particles and ragweed allergen in vivo induce TH2 cytokine production in the nasal mucosa of ragweed-sensitive subjects