Antigen-induced Eosinophil Recruitment Research Articles

Proteinase-activated receptor 2 blockade impairs CCL11- or allergen-induced eosinophil recruitment in experimental pleurisy

Although proteinase-activated receptor (PAR)-2 has been implicated in inflammatory diseases, its role in regulating eosinophil recruitment in response to chemoattractants remains unclear. Here, we investigated the role of PAR-2 and PAR-2-activating Mast Cell (MC) tryptase on chemokine C–C motif ligand (CCL)11- and antigen-induced eosinophil recruitment to the pleural cavity of BALB/c mice. The PAR-2-activating peptide H–Ser–Leu–Ile–Gly–Arg–Leu–NH2 (SLIGRL–NH2) induced eosinophil recruitment whereas PAR-2 blockade inhibited ovalbumin (OVA)- or CCL11-induced eosinophil recruitment. Moreover, OVA and CCL11 induced PAR-2 expression in pleural leukocytes, and the MC tryptase inhibitor APC 366 ([N-(1-hydroxy-2-napthoyl)-l-arginyl-l-prolinamide hydrochloride]) abolished CCL11-induced eosinophil recruitment. These results suggest a pro inflammatory effect of PAR-2 and support a role for MC tryptase mediating eosinophil migration via PAR-2 signaling. Taken together, our results suggest that PAR-2 activation through endogenous MC tryptase activity could be required, at least partially, to mediate CCL11-induced eosinophil migration.

IL-22 attenuates IL-25 production by lung epithelial cells and inhibits antigen-induced eosinophilic airway inflammation

IL-22 functions as both a proinflammatory cytokine and an anti-inflammatory cytokine in various inflammations, depending on the cellular and cytokine milieu. However, the roles of IL-22 in the regulation of allergic airway inflammation are still largely unknown. We sought to determine whether IL-22 is involved in the regulation of allergic airway inflammation. We examined IL-22 production and its cellular source at the site of antigen-induced airway inflammation in mice. We also examined the effect of IL-22 neutralization, as well as IL-22 administration, on antigen-induced airway inflammation. We finally examined the effect of IL-22 on IL-25 production from a lung epithelial cell line (MLE-15 cells). Antigen inhalation induced IL-22 production in the airways of sensitized mice. CD4(+) T cells, but not other lymphocytes or innate cells, infiltrating in the airways produced IL-22, and one third of IL-22-producing CD4(+) T cells also produced IL-17A. The neutralization of IL-22 by anti-IL-22 antibody enhanced antigen-induced IL-13 production, eosinophil recruitment, and goblet cell hyperplasia in the airways. On the other hand, intranasal administration of recombinant IL-22 attenuated antigen-induced eosinophil recruitment into the airways. Moreover, anti-IL-22 antibody enhanced antigen-induced IL-25 production in the airways, and anti-IL-25 antibody reversed the enhancing effect of anti-IL-22 antibody on antigen-induced eosinophil recruitment into the airways. Finally, IL-22 inhibited IL-13-mediated enhancement of IL-25 expression in IL-1β- or LPS-stimulated MLE-15 cells. IL-22 attenuates antigen-induced airway inflammation, possibly by inhibiting IL-25 production by lung epithelial cells.

IL-23 and Th17 Cells Enhance Th2-Cell–mediated Eosinophilic Airway Inflammation in Mice

The IL-23-IL-17A-producing CD4(+) T-cell (Th17 cell) axis plays an important role in the development of chronic inflammatory diseases, including autoimmune diseases. However, the role of the IL-23-Th17 cell axis in the regulation of allergic airway inflammation is still largely unknown. To determine the role of IL-23 and Th17 cells in allergic airway inflammation. We examined the effect of anti-IL-23 antibody on antigen-induced airway inflammation. We also investigated the effect of enforced expression of IL-23 on allergic airway inflammation by generating lung-specific IL-23 transgenic mice. Moreover, we examined the effect of adoptive transfer of antigen-specific Th17 cells on allergic airway inflammation. IL-23 mRNA was expressed in the lung of sensitized mice upon antigen inhalation, and the neutralization of IL-23 decreased antigen-induced eosinophil recruitment and Th2 cytokine production in the airways. The enforced expression of IL-23 in the airways significantly enhanced antigen-induced eosinophil and neutrophil recruitment into the airways; Th2 cytokine, IL-17A, and tumor necrosis factor (TNF)-alpha production in the airways; goblet cell hyperplasia; and airway hyperresponsiveness. Moreover, IL-23-mediated enhancement of antigen-induced Th2 cytokine production and eosinophil recruitment in the airways was still observed in the mice lacking IL-17A. Furthermore, although adoptive transfer of antigen-specific Th17 cells alone induced neutrophil but not eosinophil recruitment into the airways upon antigen inhalation, cotransfer of Th17 cells with Th2 cells significantly enhanced antigen-induced Th2-cell-mediated eosinophil recruitment into the airways and airway hyperresponsiveness. IL-23 and Th17 cells not only induce Th17-cell-mediated neutrophilic airway inflammation but also up-regulate Th2-cell-mediated eosinophilic airway inflammation.

GS143, an IκB ubiquitination inhibitor, inhibits allergic airway inflammation in mice

Asthma is characterized by airway inflammation with intense eosinophil infiltration and mucus hyper-production, in which antigen-specific Th2 cells play critical roles. Nuclear factor-κB (NF-κB) pathway has been demonstrated to be essential for the production of Th2 cytokines and chemokines in the airways in murine asthma models. In the present study, we examined the effect of GS143, a novel small-molecule inhibitor of IκB ubiquitination, on antigen-induced airway inflammation and Th2 cytokine production in mice. Intranasal administration of GS143 prior to antigen challenge suppressed antigen-induced NF-κB activation in the lung of sensitized mice. Intranasal administration of GS143 also inhibited antigen-induced eosinophil and lymphocyte recruitment into the airways as well as the expression of Th2 cytokines and eotaxin in the airways. Moreover, GS143 inhibited antigen-induced differentiation of Th2 cells but not of Th1 cells in vitro. Taken together, these results suggest that IκB ubiquitination inhibitor may have therapeutic potential against asthma.

B and T Lymphocyte Attenuator Inhibits Antigen-Induced Eosinophil Recruitment into the Airways

Background: Signaling through CD28 family co-receptors regulates activation of CD4⁺ T cells positively and negatively. It has been shown that stimulatory co-receptors such as CD28 and ICOS play critical roles in the induction of allergic airway inflammation. However, the role of B and T lymphocyte attenuator (BTLA), an inhibitory co-receptor expressed preferentially in Th1 cells, in the regulation of allergic airway inflammation remains to be determined. Methods: We examined antigen-induced eosinophil recruitment and cytokine production in the airways in antigen-sensitized BTLA-deficient (BTLA–/–) mice. We also examined antigen-induced cytokine production and cell proliferation of splenic T cells in antigen-sensitized BTLA–/– mice. Results: Antigen-induced eosinophil recruitment and IL-5 production in the airways was enhanced in antigen-sensitized BTLA–/– mice. On the other hand, antigen-induced Th1 and Th2 cytokine production as well as T cell proliferation of splenocytes was normal in BTLA–/–mice. Conclusion: BTLA inhibits antigen-induced eosinophil recruitment into the airways by preventing IL-5 production from Th2 cells.

Effect of tecastemizole on pulmonary and cutaneous allergic inflammatory responses

Tecastemizole, a major metabolite of astemizole, is a potent and selective H1 receptor antagonist. Evidence suggests that this and certain other H1 receptor antagonists may possess anti-inflammatory effects that are, in some cases, independent of H1 receptor antagonism. Objective The aim of this study was to investigate the anti-inflammatory effects of tectastemizole in models of allergic inflammation. Effects of tecastemizole were assessed in a murine model of allergic lung inflammation, in passive cutaneous anaphylaxis (PCA) responses in guinea-pig skin and in in vitro assays measuring endothelial adhesion molecule expression and leucocyte-endothelial adhesion. Tecastemizole inhibited antigen-induced eosinophil recruitment to the lungs of allergic mice in a dose-dependent manner. Furthermore, combination of a sub-effective dose of tecastemizole, combined with a sub-effective dose of dexamethasone inhibited eosinophil accumulation in this model. Plasma extravasation in PCA reactions was inhibited by tecastemizole, although by a mechanism that would appear to be H1 receptor-dependent. Cytokine-induced endothelial intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression, as well as mononuclear cell adhesion to human umbilical vein endothelial cells was inhibited by tecastemazole in a manner independent of H1 receptor antagonism. These data suggest that tecastemizole may have H1 receptor-independent effects in inhibiting late-phase inflammatory responses, while acute responses appear to be inhibited in a H1 receptor-dependent manner. Furthermore, our data suggest an important potential steroid-sparing role for such drugs in the treatment of allergic inflammatory conditions.

T-bet inhibits both T H2 cell–mediated eosinophil recruitment and T H17 cell–mediated neutrophil recruitment into the airways

Previous studies have shown that mice lacking T-bet, a critical transcription factor for T(H)1 cell differentiation, spontaneously develop airway inflammation with intense eosinophil infiltrates. However, the mechanism underlying T-bet-mediated inhibition of allergic airway inflammation is still unknown. To determine the regulatory role of T-bet in antigen-induced allergic airway inflammation. We examined the role of T-bet in antigen-induced allergic airway inflammation using T-bet(-/-) mice on a BALB/c background that did not develop spontaneous airway inflammation. We also examined the role of T-bet expression of CD4(+) T cells in airway inflammation by adoptive transfer experiments. We found that antigen-induced eosinophil recruitment, goblet cell hyperplasia, and T(H)2 cytokine production in the airways were enhanced in T-bet(-/-) mice. However, in the absence of signal transducer and activator of transcription 6 (STAT6), T-bet deficiency could not induce the antigen-induced eosinophilic airway inflammation. Adoptive transfer of T-bet(-/-) or T-bet(+/+) CD4(+) T cells to T-bet(-/-)Rag-2(-/-) mice revealed that the expression of T-bet in CD4(+) T cells was vital for the inhibition of antigen-induced eosinophilic airway inflammation. Interestingly, antigen-induced neutrophil recruitment in the airways was also enhanced in T-bet(-/-) mice. Moreover, T-bet(-/-) CD4(+) T cells preferentially differentiated into IL-17-producing cells that mediated neutrophilic airway inflammation. T-bet inhibits both T(H)2 cell-mediated eosinophilic inflammation and T(H)17 cell-mediated neutrophilic inflammation in the airways. The dysfunction of T-bet may be involved in the pathogenesis of severe asthma, in which accumulation of neutrophils as well as eosinophils in the airways is a hallmark of disease.

IL-25 enhances allergic airway inflammation by amplifying a T H2 cell–dependent pathway in mice

A novel IL-17 family cytokine, IL-25, has been reported to induce IL-4, IL-5, and IL-13 production from undefined non-T/non-B cells and then induce T(H)2-type immune responses. However, the roles of IL-25 in inducing allergic airway inflammation remain unknown. We sought to determine whether IL-25 is involved in causing allergic airway inflammation. We examined the expression of IL-25 mRNA in the lungs of sensitized mice on antigen inhalation. We also examined the effect of IL-25 neutralization by soluble IL-25 receptor on antigen-induced airway inflammation. We then generated IL-25 transgenic mice that express IL-25 specifically in the lung under the control of the Clara cells-10-kd protein promoter and investigated the effect of enforced IL-25 expression on antigen-induced airway inflammation. IL-25 mRNA was expressed in the lungs of sensitized mice on antigen inhalation, and the neutralization of IL-25 by soluble IL-25 receptor decreased antigen-induced eosinophil and CD4(+) T-cell recruitment into the airways. The enforced expression of IL-25 in the lung itself failed to induce allergic airway inflammation, whereas the expression of IL-25 significantly enhanced antigen-induced T(H)2 cytokine production, eosinophil and CD4(+) T cell recruitment, and goblet cell hyperplasia in the airways. Moreover, IL-25-induced enhancement of allergic airway inflammation was inhibited by the depletion of CD4(+) T cells or by the absence of signal transducer and activator of transcription 6. IL-25 enhances antigen-induced allergic airway inflammation by amplifying a T(H)2 cell-dependent pathway. IL-25 might be involved in the enhancement, prolongation, or both of T(H)2 cell-mediated allergic diseases, such as asthma.

Interleukin 25 in Allergic Airway Inflammation

T helper 2 (Th2) cells induce allergic inflammation through the production of cytokines such as interleukin (IL)-4, IL-5 and IL-13. Recently, it has been demonstrated that a novel IL-17 family cytokine IL-25 (IL-17E) is a product of activated Th2 cells and mast cells. Interestingly, when systemically administered to mice, IL-25 induces IL-4, IL-5 and IL-13 production from undefined non-T/non-B cells and then induces Th2-type immune responses such as blood eosinophilia and increased serum immunoglobulin E levels. In addition, we have recently shown that IL-25 mRNA is expressed in the lung after an inhaled antigen challenge in sensitized mice and that neutralization of the produced IL-25 by soluble IL-25 receptor decreases antigen-induced eosinophil and CD4+ T cell recruitment into the airways. Moreover, we have shown that the enforced expression of IL-25 in the lung significantly enhances antigen-induced Th2 cytokine production and eosinophil recruitment into the airways, and that the IL-25-mediated enhancement of antigen-induced eosinophil recruitment is inhibited by the depletion of CD4+ T cells. Thus, it is suggested that IL-25 plays an important role in enhancing allergic airway inflammation by a CD4+ T-cell-dependent mechanism.

Quantitative expression levels of regulated on activation, normal T cell expressed and secreted and eotaxin transcripts in toluene diisocyanate-induced allergic rats

ConclusionThese results suggest that eotaxin may play a predominant role in controlling antigen-induced eosinophil recruitment into tissue.ObjectiveTo investigate the expression levels of regulated on activation, normal T cell expressed and secreted (RANTES) mRNA and eotaxin mRNA in the nasal mucosa of toluene diisocyanate (TDI)-induced allergic rats and to evaluate which of them is primarily related to selective eosinophilic infiltration by comparing their expression levels with the numbers of infiltrated eosinophils and vascular cell adhesion molecule-1 (VCAM-1).Material and methodsWe quantified the expression levels of two strong eosinophilic CC chemokines (RANTES and eotaxin) and VCAM-1 at mRNA levels in the nasal mucosa of TDI-induced allergic rats using competitive polymerase chain reaction and compared their expression levels with the number of infiltrated eosinophils.ResultsThe number of infiltrated eosinophils was significantly increased between 3 h and Day 4 in TDI-induced allergic rats, but had decreased by Day 5. VCAM-1 mRNA expression was also increased between 3 h and Day 4. The number of infiltrated eosinophils correlated with the expression levels of VCAM-1 mRNA (p<0.01). In contrast, expression of RANTES mRNA and eotaxin mRNA was increased between 3 h and Day 2, peaked between Days 1 and 2 and then declined. Although the expression of both chemokines correlated with the numbers of infiltrated eosinophils (p<0.01), peak expression levels of eotaxin mRNA were 14-fold higher than baseline levels whereas RANTES mRNA expression increased 3-fold.

Effect of a novel interleukin-5 receptor antagonist, YM-90709, on antigen-induced eosinophil infiltration into the airway of BDF1 mice

A newly synthesized compound, YM-90709, 2,3-dimethoxy-6,6-dimethyl-5,6-dihydrobenzo[7,8]indolizino[2,3- b]quinoxaline, was previously reported to specifically inhibit the binding of interleukin-5 (IL-5) to its receptor (R) on human eosinophils. In this study, the intravenous injection of YM-90709 inhibited antigen-induced infiltration of eosinophils into the bronchoalveolar lavage fluid (BALF) of BDF1 mice, with an ED 50 value of 0.050 mg/kg. Anti-murine IL-5 monoclonal antibody (mAb) also inhibited the infiltration of eosinophils with an ED 50 value of 0.035 mg/kg. These results indicate that YM-90709, which is a novel IL-5R antagonist, inhibits antigen-induced eosinophil recruitment into the airway, the same as anti-IL-5 mAb does.

Effect of a novel interleukin-5 receptor antagonist, YM-90709 (2,3-dimethoxy-6,6-dimethyl-5,6-dihydrobenzo[7,8]indolizino[2,3- b]quinoxaline), on antigen-induced airway inflammation in BN rats

Interleukin-5 (IL-5) plays an important role in the activation of eosinophils in the allergic inflammation in conditions such as asthma, rhinitis, and atopic dermatitis. A newly synthesized compound, YM-90709 (2,3-dimethoxy-6,6-dimethyl-5,6-dihydrobenzo[7,8]indolizino[2,3- b]quinoxaline), was previously reported to inhibit the binding of IL-5 to its receptor (R) on human eosinophils and eosinophilic HL-60 clone 15 cells. However, it did not inhibit the binding of granulocyte-macrophage colony-stimulating factor (GM-CSF) to its receptor on the same cells. In this study, the intravenous injection of YM-90709 resulted in the inhibition of antigen-induced infiltration of eosinophils and lymphocytes, but not neutrophils or monocytes, into the bronchoalveolar lavage fluid (BALF) of Brown-Norway (BN) rats, with ED 50 values of 0.32 mg/kg and 0.12 mg/kg, respectively. Two glucocorticoids, dexamethasone and prednisolone, inhibited neutrophil, eosinophil, and lymphocyte infiltration into the BALF. However, both significantly reduced the number of peripheral blood leukocytes and bone marrow leukocytes. In contrast, YM-90709 did not affect the peripheral blood leukocytes or the bone marrow leukocytes. These results indicate that, in this model, YM-90709, which is a novel IL-5 R antagonist, inhibits antigen-induced eosinophil and lymphocyte recruitment into the airway, without any suppressive effects on peripheral blood leukocytes or bone marrow leukocytes, in contrast to the glucocorticoids.

Lactic dehydrogenase virus (LDV) infection inhibits allergic eosinophil reaction in the airway

The effects of interferon (IFN)-γ induced by virus infection on eosinophil reaction in allergic airway inflammation are not yet clear. We investigated the effects of lactic dehydrogenase virus (LDV) infection, which increases IFN -γ production with no viral infection or replication in respiratory epithelium, on allergic airway hypersensitivity. LDV infection suppressed antigen-induced eosinophil recruitment into the airway in sensitized mice. IL -5 gene expression in bronchoalveolar lavage (BAL) cells was significantly suppressed in LDV -infected mice compared with uninfected controls. The numbers of total T cells and CD 4+ T cells were significantly reduced in LDV -infected mice compared with controls. The present results suggested that the increase in production ofIFN -γ by viral infection suppresses the eosinophil reaction, and this suppressive effect may be mediated by inhibition of the recruitment of CD 4+ T cell and IL -5 production.

Lipid A Analogue, ONO-4007, Inhibits IgE Response and Antigen-Induced Eosinophilic Recruitment into Airways in BALB/c Mice

Background: Since antigen-specific IgE and eosinophils are major inducing factors of allergic inflammation of the airways, both factors are therapeutic targets of asthma. We investigated the effects of ONO-4007, a nontoxic lipid A analogue, on antigen-specific antibody response and the recruitment of eosinophils into airways in murine systems. Methods: BALB/c mice were injected ONO-4007 intraperitoneally during sensitization with ovalbumin (OVA) and aluminium hydroxide to determine its effects on the antigen-specific antibody response. ONO-4007 was also injected intravenously during either systemic sensitization and inhalation with OVA, or sensitization or inhalation alone to determine its effects on antigen-induced airway inflammation. In vitro effects of ONO-4007 on the functional differentiation of naive CD4⁺ T cells were investigated by culturing naive CD4⁺ T cells derived from DO11.10 mice and OVA-pulsed dendritic cells (CDCs) with ONO-4007. Results: ONO-4007 inhibited antigen-specific IgE and IgG₁, but not IgG_2a responses. ONO-4007 decreased the recruitment of eosinophils and the levels of IL-5 in bronchoalveolar lavage fluid, not only when it was injected during systemic sensitization and inhalation with OVA, but also during inhalation alone. ONO-4007 inhibited the differentiation of IL-4- and IL-13-producing CD4⁺ T cells in vitro, which was partly mediated by DCs. Conclusions: ONO-4007 inhibited antigen-specific IgE and IgG₁ responses and antigen-induced eosinophil recruitment into the airways in BALB/c mice. These effects were mediated, at least partly, by the modulation of DCs, although there may also be other mechanisms.

Role of CD4(+) CD25(+) regulatory T cells in T helper 2 cell-mediated allergic inflammation in the airways.

It has recently been shown that CD4(+) CD25(+) T cells are immunoregulatory T cells that prevent CD4(+) T cell-mediated organ-specific autoimmune diseases. To determine whether CD4(+) CD25(+) T cells downregulate Th2 cell-mediated allergic inflammation in the airways, we studied antigen-induced eosinophil recruitment in the airways in BALB/c Rag-2(-)(/-) mice transferred with CD4(+) CD25(+) T cell-depleted or unfractionated T cells from ovalbumin-specific TCR transgenic mice. Antigen-induced eosinophil recruitment into the airways was significantly decreased in the mice transferred with CD4(+) CD25(+) T cell-depleted splenocytes as compared with those transferred with unfractionated splenocytes. On the other hand, the depletion of CD4(+) CD25(+) T cells increased antigen-induced neutrophil and T cell recruitment in the airways of the mice. The depletion of CD4(+) CD25(+) T cells also decreased antigen-induced IL-4 and IL-5 production in the airways of the mice. Finally, the depletion of CD4(+) CD25(+) T cells prevented antigen-induced Th2 cell differentiation in vitro but increased the differentiation of Th1 cells. These results indicate that CD4(+) CD25(+) T cells modulate the Th1 and Th2 cell balance toward Th2 cells and thus upregulate Th2 cell-mediated allergic inflammation in the airways.

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.

The role of Jak 2 and Stat 5 in antigen-induced eosinophil recruitment into the airways

We studied the role of Jak 2 and Stat 5 in antigen-induced eosinophil recruitment into the airways of sensitized mice. The in vivo administration of a Jak 2 inhibitor AG-490 prevented antigen induced eosinophil recruitment into the airways of sensitized mice in a dose-dependent manner, whereas the administration of AG-490 did not affect antigen induced IL-5 production in the airways. On the other hand, both antigen induced IL -5 production and antigen induced airway eosinophilia was diminished in Stat 5 a-deficient (Stat 5 a-/-) mice and Stat 5 b-deficient (Stat 5 b-/-) mice. In addition, eosinophilopoiesis induced by the administration of recombinant IL-5 was diminished in Stat 5 a-/- mice and Stat 5 b-/- mice. Interestingly, antigen-induced Th 2 cell differentiation was decreased but antigen-induced Th 1 cell differentiation was increased in Stat 5 a-/- mice. Together, these results indicate that Jak 2 and Stat 5 activation are essential for the induction of IL-5-dependent, antigen-induced eosinophil recruitment into the airways and that the defects in antigen induced eosinophil recruitment in Stat 5 a-/- mice and Stat 5 b-/- mice result from both impaired IL -5 production in the airways and diminished IL -5 responsiveness of eosinophils.

Synthesis, structure-activity relationships, and pharmacological profile of 9-amino-4-oxo-1-phenyl-3,4,6,7-tetrahydro[1,4]diazepino[6, 7,1-hi]indoles: discovery of potent, selective phosphodiesterase type 4 inhibitors.

The synthesis, structure-activity relationships, and biological properties of a novel series of potent and selective phosphodiesterase type 4 (PDE4) inhibitors are described. These new aminodiazepinoindoles displayed in vitro PDE4 activity with submicromolar IC(50) values and PDE4 selectivity vs PDE1, -3, and -5. Specifically, one compound (CI-1044, 10e) provided efficient in vitro inhibition of TNFalpha release from hPBMC and hWB with IC(50) values of 0.34 and 0.84 microM, respectively. This compound was found to exhibit potent in vivo activity in antigen-induced eosinophil recruitment in Brown-Norway rats (ED(50) = 3.2 mg/kg po) and in production of TNFalpha in Wistar rats (ED(50) = 2.8 mg/kg po). No emetic side effects at therapeutic doses were observed in ferrets.

Systemic T Helper 2 Cell Activation Is Not Sufficient for Antigen-Induced Eosinophil Recruitment into the Airways

Background: Airway eosinophilic inflammation is a characteristic feature of asthma. We have previously shown that antigen-induced eosinophil recruitment into the airways of sensitized BALB/c mice is mediated by CD4+ T cells and IL-5. However, the basis for the eosinophil recruitment into the airway are still largely unknown. Methods: To determine the regulatory mechanisms that control the magnitude of antigen-induced eosinophilic inflammation in the airways, we analyzed antigen-induced eosinophil and T cell infiltration into the trachea in several strains of mice, including BALB/c (H-2^d), BALB/b (H-2^b), C57BL/6 (H-2^b), C57BL/10 (H-2^b), and B10.D2 (H-2^d) mice. In addition, cytokine production from antigen-stimulated splenocytes and the titer of antigen-specific IgE antibody in serum were assessed. Results: Antigen-induced eosinophil recruitment into the trachea in BALB/c mice was more than 20 times as abundant as that in C57BL/6 mice, the latter of which was also mediated by CD4+ T cells. In contrast, systemic Th2 responses, which were evaluated by the titers of antigen-specific IgE antibody in serum and antigen-induced IL-4 and IL-5 production from splenocytes, were similarly observed in BALB/c mice and C57BL/6 mice. In addition, the antigen-induced eosinophil recruitment into the trachea was high in BALB/b mice, like BALB/c mice, but low in B10.D2 mice. Conclusions: Systemic Th2 responses are not sufficient for causing antigen-induced eosinophil recruitment into the airways and an undefined determinant(s) that exists in the BALB background mice rather than the H-2 haplotype is vital for the regulation of antigen-induced eosinophil recruitment into the airways.

Blockade of JAK2 by Tyrphostin AG-490 Inhibits Antigen-Induced Eosinophil Recruitment into the Mouse Airways

We studied the effect of tyrphostin AG-490, a specific Janus kinase 2 (JAK2) inhibitor, on antigen-induced eosinophil recruitment into the airways of sensitized mice and on IL-5-induced chemokinesis and adhesiveness of eosinophils. The in vivo administration of AG-490 prevented antigen-induced eosinophil infiltration in the airways of sensitized mice in a dose-dependent manner. However, the administration of AG-490 did not affect antigen-induced IL-5 production in the airways nor in vitro antigen-induced IL-5 production and T cell proliferation of spleen cells. Furthermore, AG-490 inhibited IL-5-induced chemokinesis and β1-integrin adhesiveness of eosinophils in vitro. Because antigen-induced eosinophil recruitment into the airways is mediated by IL-5, these results indicate that JAK2 activation is critical for antigen-induced, IL-5-dependent mobilization of eosinophils into the tissue.