Interleukin-5-producing CD4+ T cells play a pivotal role in aeroallergen-induced eosinophilia, bronchial hyperreactivity, and lung damage in mice

Although activated CD4+ T cells have been implicated in the pathogenesis of asthma, the direct contribution of this leukocyte to the induction of aeroallergen-induced bronchial hyperreactivity and lung damage is unknown. In the present investigation, we have used a model of allergic airways inflammation, which displays certain phenotypic characteristics of late-phase asthmatic responses, together with interleukin-5-deficient (IL-5-/- ) mice and donor antigen-specific CD4+ TH2-type cells to obtain unequivocal evidence for a role of this T lymphocyte in the pathophysiology of allergic airways inflammation. Antigen-primed CD4+ T cells and CD4- cells (CD4+-depleted population) were purified from the spleens of ovalbumin (OVA)-sensitized wild-type mice and adoptively transferred to OVA-sensitized and nonsensitized IL-5-/- mice. In vitro stimulation of the purified cell populations with OVA resulted in the secretion of IL-4 and IL-5, but not interferon-gamma, from the CD4+ T cells, indicating that they were of the TH2 type. In contrast, interferon-gamma, but not IL-4 and IL-5, was produced by the CD4- T cells. The CD4+ TH2-type cells (but not the CD4 cells) reconstituted aeroallergen (OVA)-induced blood and airways eosinophilia, lung damage, and airways hyperreactivity to 1-methacholine in IL-5-/- mice. The reconstitution did not require prior sensitization of the mice, but it did not occur if they were aerosolized with saline instead of OVA. The circulating levels of OVA-specific -IgE and -IgG1 were not significantly altered by the adoptive transfer of either cell population. These investigations establish that IL-5-secreting CD4+ TH2-type cells play a pivotal role in generating blood and airways eosinophilia and in the subsequent development of bronchial hyperreactivity and lung damage that occurs in response to aeroallergens.     

Requirements for allergen-induced airway hyperreactivity in T and B cell-deficient mice

BACKGROUND: The pathogenesis of asthma is believed to reflect antigen-induced airway inflammation leading to the recruitment of eosinophils and activation of mast cells through cell-associated IgE. Controversies persist however, regarding the relative importance of different pathogenic cells and effector molecules. MATERIALS AND METHODS: A variety of gene-targeted mice were examined for the induction of cholinergic airway hyperresponsiveness (AH), allergic airway inflammation, mucus production, and serum IgE reactivity following intratracheal challenge with a potent allergen. AH was determined using whole-body plethysmography following acetylcholine challenge. Where possible, results were confirmed using neutralizing antibodies and cell-specific reconstitution of immune deficient mice. RESULTS: T and B cell-deficient, recombinase-activating-gene-deficient mice (RAG -/-) failed to develop significant allergic inflammation and AH following allergen challenge. Reconstitution of RAG -/- mice with CD4+ T cells alone was sufficient to restore allergen-induced AH, allergic inflammation, and goblet cell hyperplasia, but not IgE reactivity. Sensitized B cell-deficient mice also developed airway hyperreactivity and lung inflammation comparable to that of wild-type animals, confirming that antibodies were dispensable. Treatment with neutralizing anti-IL-4 antibody or sensitization of IL-4-deficient mice resulted in loss of airway hyperreactivity, whereas treatment with anti-IL-5 antibody or sensitization of IL-5-deficient mice had no effect. CONCLUSIONS: In mice, CD4+ T cells are alone sufficient to mediate many of the pathognomonic changes that occur in human asthma by a mechanism dependent upon IL-4, but independent of IL-5, IgE, or both. Clarification of the role played by CD4+ T cells is likely to stimulate important therapeutic advances in treatment of asthma.     

Circulating, but not local lung, IL-5 is required for the development of antigen-induced airways eosinophilia

IL-5 is induced locally in the lung and systemically in the circulation during allergic airways eosinophilic inflammation both in humans and experimental animals. However, the precise role of local and systemic IL-5 in the development of allergic airways eosinophilia remains to be elucidated. In our current study, we demonstrate that compared with their IL-5(+/+) counterparts, IL-5(-/-) mice lacked an IL-5 response both in the lung and peripheral blood, yet they released similar amounts of IL-4, eotaxin, and MIP-1alpha in the lung after ovalbumin (OVA) sensitization and challenge. At cellular levels, these mice failed to develop peripheral blood and airways eosinophilia while the responses of lymphocytes, neutrophils, and macrophages remained similar to those in IL-5(+/+) mice. To dissect the relative role of local and systemic IL-5 in this model, we constructed a gene transfer vector expressing murine IL-5. Intramuscular IL-5 gene transfer to OVA-sensitized IL-5(-/-) mice led to raised levels of IL-5 compartmentalized to the circulation and completely reconstituted airways eosinophilia upon OVA challenge, which was associated with reconstitution of eosinophilia in the bone marrow and peripheral blood. Significant airways eosinophilia was observed for at least 7 d in these mice. In contrast, intranasal IL-5 gene transfer, when rendered to give rise to a significant but compartmentalized level of transgene protein IL-5 in the lung, was unable to reconstitute airways eosinophilia in OVA-sensitized IL-5(-/-) mice upon OVA-challenge, which was associated with a lack of eosinophilic responses in bone marrow and peripheral blood. Our findings thus provide unequivocal evidence that circulating but not local lung IL-5 is critically required for the development of allergic airways eosinophilia. These findings also provide the rationale for developing strategies to target circulating IL-5 and/or its receptors in bone marrow to effectively control asthmatic airways eosinophilia.     

Cytokines as targets for the inhibition of eosinophilic inflammation

Eosinophilic inflammation is thought to play a central role in the pathogenesis of asthma. The immunoregulatory effects of interleukin (IL)-4, IL-5 and immunoglobulin (Ig)E suggest that these molecules play key roles in the effector function of eosinophils and mast cells. IL-4 regulates the development of CD4+ TH2-type cells, which elicit essential signals through IL-4 and IL-5 for the regulation of IgE production and eosinophilia, respectively. IL-5-regulated pulmonary eosinophilia and airways dysfunction can also occur independently of IL-4 and allergen-specific Igs. Such IL-4-independent pathways may also play a substantive role in the aetiology of asthma. Thus, evidence is now emerging that allergic airways disease is regulated by humoral and cell-mediated components. The essential and specific role of IL-5 in regulating eosinophilia, and the subsequent involvement of this leukocyte in the induction of lung damage and airways dysfunction, identifies IL-5 as a primary therapeutic target for the relief of airways dysfunction in asthma.     

Lack of both types 1 and 2 cytokines, tissue inflammatory responses, and immune protection during pulmonary infection by Mycobacterium bovis bacille Calmette-Guérin in IL-12-deficient mice

Understanding of key cytokines and the nature of protective immune responses in pulmonary mycobacterial diseases remains a task of paramount importance. In this study, both wild-type (wt) and IL-12-deficient (IL-12(-/-)) mice were infected by airways inoculation of live Mycobacterium bovis bacille Calmette-Guérin (BCG). The type 1 cytokines IL-12, IFN-gamma, and TNF-alpha, but not the type 2 cytokines IL-4 and granulocyte macrophage (GM)-CSF, markedly increased in the lung and peripheral blood of wt mice postinfection, which resulted in the development of intense granulomatous responses and the effective control of mycobacterial infection in the lung. In contrast, IL-12(-/-) mice demonstrated a lack of both types 1 and 2 cytokines in the lung and blood and a severely impaired tissue immune-inflammatory response lacking not only macrophages and neutrophils but CD4 and CD8 T cells and NK cells in the lung throughout the entire course of study. Total lung mononuclear cells isolated from these mice, in contrast to wt mice, had an impaired recall immune response to Ag challenge in vitro. These impaired responses resulted in an uncontrolled local growth and systemic spread of bacilli. Our findings reveal that IL-12 plays an irreplaceable role in the initiation of Th1 responses, and the loss of its function cannot be compensated for by alternative mechanisms in the lung. This cytokine, together with IFN-gamma and TNF-alpha, and granulomatous inflammation are critically required for the effective control of pulmonary mycobacterial infection. Our results also indicate that the absence of type 1 cytokines does not necessarily favor a Th2 response.     

Cytokine and eosinophil responses in the lung, peripheral blood, and bone marrow compartments in a murine model of allergen-induced airways inflammation

Selective accumulation of eosinophils and activated CD4+ cells is now considered a central event in the pathogenesis of asthma, and this process is thought to be mediated by a number of cytokines including tumor necrosis factor-alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), and the Type 2 cytokines interleukin-4 (IL-4) and IL-5. To carry out a detailed time-course analysis of cellular changes in the bronchoalveolar lavage fluid (BAL), peripheral blood (PB), and bone marrow (BM), and of changes in the aforementioned cytokines in BAL and serum, Balb/c mice were sensitized by intraperitoneal injection with ovalbumin (OVA) adsorbed to aluminum hydroxide on two occasions 5 days apart, and were subjected to an OVA aerosol challenge 12 days after the second sensitization. This resulted in an airways inflammatory response characterized by early transient neutrophilia, marked eosinophilia, and, to a lesser extent, lymphocytosis in the BAL. Inflammatory events were first observed 3 h and 24 h after antigen challenge in the lung tissue and BAL, respectively, and lasted for 21 days. In the BM, we detected a 1.5- and 5-fold increase in the total number of cells and eosinophils, respectively, 4 days after the second sensitization. This was followed by a decrease, although BM eosinophilia remained clearly present at the time of antigen challenge. A second eosinopoietic event was observed in the BM shortly after challenge and reached a peak at day 3. BM cellularity returned to normal at day 21 after challenge. Serum OVA-specific IgE was first detected 3 days following the second sensitization (150 ng/ml). IgE levels then decreased but remained at the 75 ng/ml range at the time of the aerosol challenge. During the sensitization period, TNF-alpha (approximately 25 pg/ml), IL-4 (approximately 40 pg/ml), and IL-5 (approximately 250 pg/ml) were detected in serum, but not in the BAL fluid (BALF) and returned to background levels at the time of the antigen challenge. After antigen challenge, TNF-alpha, IL-4, IL-5, and GM-CSF were detected in serum. Peak levels were observed at 3 h (approximately 40 pg/ml), 3 h (approximately 120 pg/ml), 12 h (approximately 350 pg/ml), and 3 h (approximately 10 pg/ml), respectively, and returned to background levels 24 h after challenge. In the BALF, we detected peak levels of TNF-alpha, IL-4, IL-5, and GM-CSF at 6 h (approximately 250 pg/ml), 24 h (approximately 140 pg/ml), 24 h (350 pg/ml), and 3 h (approximately 10 pg/ml), respectively, with a return to background levels 5 days after challenge. No IL-10 could be detected at any time point during sensitization or after challenge in either serum or BAL. We also detected approximately 40 pg/ml of interferon-gamma (IFN-gamma) in the serum of normal untreated mice. Serum IFN-gamma levels fluctuated during sensitization and after challenge, but never exceeded those observed in untreated mice. Thus, the cytokine profile observed in this experimental model of allergic inflammation is characterized by IL-4 and IL-5 dominance, with an apparently minor TNF-alpha and GM-CSF contribution and relatively low or undetectable levels of IFN-gamma and IL-10.     

Inhibition of interleukin-5 with a monoclonal antibody attenuates allergic inflammation

IL-5 is a prominent and perhaps an essential element in the induction of allergic inflammation in human asthma and other allergic diseases. Despite the strong biochemical and clinical correlates between lung eosinophilia and asthma, there is no clear understanding of how eosinophils exacerbate asthma. Antigen administration to sensitized animals produces eosinophilic infiltration that is very similar to that in man, and is prevented by administration of a neutralizing monoclonal antibody against IL-5. Mice in which the IL-5 gene is absent are unable to mount eosinophilic responses to antigen and do not sustain lung damage, but otherwise develop normally. The study of the biology of IL-5 has not only clarified the links between eosinophilia and airway hyperreactivity, but also strongly suggests that anti-IL-5 therapy may be an effective, safe, and novel way of treating human asthma and perhaps other eosinophilic diseases. There are many different potential approaches to the inhibition of IL-5, but the one most likely to provide "proof of principle" in "asthma in the wild" in man is a monoclonal antibody against IL-5.     

Interleukin-9 promotes allergen-induced eosinophilic inflammation and airway hyperresponsiveness in transgenic mice

Human atopic asthma is a complex heritable inflammatory disorder of the airways associated with clinical signs of allergic inflammation and airway hyperresponsiveness. Recent studies demonstrate that the degree of airway responsiveness is strongly associated with interleukin (IL)-9 expression in murine lung. To investigate the contribution of IL-9 to airway hyperresponsiveness, and to explore directly its relationship to airway inflammation, we studied transgenic mice overexpressing IL-9. In this report we show that IL-9 transgenic mice (FVB/N-TG5), in comparison with FVB/NJ mice, display significantly enhanced eosinophilic airway inflammation, elevated serum total immunoglobulin E, and airway hyperresponsiveness following lung challenge with a natural antigen (Aspergillus fumigatus). These data support a central role for IL-9 in the complex pathogenesis of allergic inflammation.     

Eosinophils are not required to induce airway hyperresponsiveness after nematode infection

Eosinophilic inflammation of the airways is believed to play a central role in the pathogenesis of bronchial asthma. Inoculation of mice with the nematode Nippostrongylus brasiliensis induces pulmonary inflammation, characterized by a marked infiltration of eosinophils, subsequent to the migration of parasites through the lungs. Infection is associated with polarized Th2 responses in different strains of mice tested. Thus, this model may be useful to determine the relationship between established pulmonary eosinophilic inflammation, Th2 immune responses and airway changes in a nonallergic background. In the present study, we have used IL-5-deficient mice to evaluate the role of IL-5 in eosinophilic lung inflammation and airway hyperresponsiveness (AHR). In wild-type C57B/6 mice, infection with N. brasiliensis resulted in eosinophil accumulation, associated with extensive lung damage characterized by hemorrhage and alveolar wall destruction, and a strong AHR following methacholine treatment. In IL-5-deficient mice, eosinophil infiltration and the associated lung damage was abrogated. Nonetheless, AHR was unimpaired. Our results suggest that eosinophil accumulation plays a central role in lung damage but is not responsible for the induction of airway constriction following N. brasiliensis infection.     

IL-13 is a key regulatory cytokine for Th2 cell-mediated pulmonary granuloma formation and IgE responses induced by Schistosoma mansoni eggs

Schistosoma mansoni egg-induced pulmonary granuloma formation is a cell-mediated inflammatory response associated with dominant Th2-type cytokine expression, tissue eosinophilia, and high levels of serum IgE. In the present study, we show that in vivo blockade of the Th2 cytokine IL-13, using soluble IL-13R alpha2-Fc fusion protein, significantly reduced the size of pulmonary granulomas in unsensitized as well as egg-sensitized mice. Blocking IL-13 also significantly reduced total serum IgE levels. Interestingly, however, IL-13 blockade did not affect the evolving egg-induced Th2-type cytokine response. IL-4, IL-5, as well as IL-13 responses were indistinguishable in control-Fc- and soluble IL-13R alpha2-Fc fusion protein-treated animals. The smaller granulomas were also phenotypically like the control Fc-treated mice, displaying a similar eosinophil content. Additional studies in IL-4-deficient mice demonstrated that IL-13 was produced, but at much lower levels than in wild-type mice, while IL-4 expression was completely independent of IL-13. Moreover, while granuloma formation was partially reduced in IL-4-deficient mice, blocking IL-13 in these animals almost completely abrogated granuloma development and the pulmonary eosinophilia, while it simultaneously increased IFN-gamma production. Together, these data demonstrate that IL-13 serves as an important mediator of Th2-mediated inflammation and plays a role in eliciting IgE responses triggered by schistosome eggs.     

TRFK-5 reverses established airway eosinophilia but not established hyperresponsiveness in a murine model of chronic asthma

We studied the effects of an anti-interleukin (IL)-5 monoclonal antibody (TRFK-5) or dexamethasone (DEX) to reverse already established airway hyperresponsiveness (AHR) and tissue eosinophilia in a Schistosoma mansoni antigen-sensitized and airway-challenged mouse model of chronic asthma. In this model at 4 d after antigen challenge there is dramatic bronchoalveolar lavage fluid (BAL) eosinophilia, AHR to intravenous methacholine (MCh), and histologic evidence of peribronchial eosinophilic infiltration and mucoid cell hyperplasia. These changes persist for up to 2 wk after antigen challenge. Treatment with DEX from Days 4 through 10 significantly reduced established airway eosinophilia compared with animals sham-treated with saline from Days 4 -10 (120 +/- 29 eosinophils/microl BAL for DEX-treated mice versus 382 +/- 60 eosinophils/microl BAL for sham-treated animals, p < 0.01). DEX-treated mice also had dramatically reduced mucoid cell hyperplasia, and airway responsiveness returned to normal. In contrast, TRFK-5 given during the same time period reduced airway eosinophilia (86 +/- 32 eosinophils/microl BAL versus 382 +/- 60 eosinophils/microl BAL, p < 0.01) but did not reduce goblet cell hyperplasia or reverse already established AHR. Treatment with DEX but not TRFK-5 also inhibited interferon gamma (IFN-gamma) content of BAL fluid (0.49 +/- 0.09 ng/ml BAL fluid for DEX versus 1.50 +/- 0.24 ng/ml BAL fluid and 1.36 +/- 0.13 ng/ml BAL fluid for TRFK-5 and sham-treated mice, respectively, both p < 0.001 versus DEX). Thus, treatment with DEX reduces established eosinophilic airway inflammation and AHR in S. mansoni-sensitized and airway-challenged mice but treatment with TRFK-5 reversed established eosinophilia without ameliorating established AHR. Together, these data suggest that once airway inflammation develops, neutralizing the effects of IL-5 or reducing eosinophilia alone may not result in inhibiting established AHR in atopic asthma.     

IL-12 is not required for induction of type 1 cytokine responses in viral infections

To investigate the physiological role of IL-12 in viral infections in terms of T cell cytokine responses involved in virus-specific Ig isotype induction and in antiviral protection, immune responses elicited upon infection of IL-12-deficient mice with lymphocytic choriomeningitis virus (LCMV) or vesicular stomatitis virus (VSV) were studied. Infection of IL-12-deficient mice with LCMV induced a virus-specific type 1 cytokine response as determined by in vitro cytokine secretion patterns as well as by in vivo intracellular cytokine staining of LCMV-specific CD4+ TCR transgenic T cells that had clonally expanded in LCMV-infected IL-12-deficient recipient mice. In addition, LCMV- and VSV-specific IgG responses exhibited normal serum IgG2a/IgG1 ratios, demonstrating again virus-specific CD4+ T cell induction of type 1 phenotype in IL-12-deficient mice upon viral infection. LCMV and VSV immune mice were found to be protected against challenge immunization with recombinant vaccinia viruses expressing either the LCMV- or the VSV-derived glycoprotein, respectively. This protection is known to be mediated by T cell-secreted type 1 cytokines IFN-gamma and TNF-alpha. In contrast, IL-12-deficient mice showed impaired abilities to control infection with the facultative intracellular bacterium Listeria monocytogenes at early time points after infection. However, at later time points of infection, IL-12-deficient mice were able to clear infection. These findings may indicate that viruses are able to induce type 1 T cell responses in the absence of IL-12 as opposed to some bacterial or parasitical infections that are crucially dependent on the presence of IL-12 for the induction of type 1 immune responses.     

Disruption of the murine IL-4 gene blocks Th2 cytokine responses

Murine T-helper clones are classified into two distinct subsets (Th1 and Th2) on the basis of their patterns of lymphokine secretion. Th1 clones secrete interleukin-2 (IL-2), tumour necrosis factor-beta (TNF-beta) and interferon-gamma (IFN-gamma), whereas Th2 clones secrete IL-4, IL-5 and IL-10 (ref. 1). These subsets are reciprocally regulated by IL-4, IL-10 and IFN-gamma and differentially promote antibody or delayed-type hypersensitivity responses. To evaluate whether IL-4 is required for mounting Th2 responses, we generated IL-4-mutant mice (IL-4-/-) and assessed the cytokine secretion pattern of T cells both from naive and Nippostrongylus brasiliensis infected mice. CD4+ T cells from naive IL-4-/- mice failed to produce Th2-derived cytokines after in vitro stimulation. The levels of Th2 cytokines IL-5, IL-9 and IL-10 from CD4+ T cells obtained after nematode infection were significantly reduced. The reduced IL-5 production in IL-4-/- mice correlated with reduced helminth-induced eosinophilia, which has been shown to be dependent on IL-5 in vivo. We conclude that IL-4 is required for the generation of the Th2-derived cytokines and that immune responses dependent on these cytokines are impaired.     

Antibody to very late activation antigen 4 prevents antigen-induced bronchial hyperreactivity and cellular infiltration in the guinea pig airways

This report examines the effect of an anti-VLA-4 monoclonal antibody (mAb) HP1/2 on antigen-induced bronchial hyperreactivity to methacholine, and on eosinophil and T lymphocyte infiltration in the airways of guinea pigs sensitized and challenged by aerosolized ovalbumin and used 24 h thereafter. The intravenous administration of 2.5 mg/kg of HP1/2, but not of its isotype-matched mAb 1E6, 1 h before and 4 h after antigen inhalation, markedly inhibited the increased bronchopulmonary responses to intravenous methacholine, as well as airway eosinophilia in bronchoalveolar lavage (BAL) fluid and in bronchial tissue. HP1/2 also suppressed the antigen-induced infiltration of the bronchial wall by CD4+ and CD8+ T lymphocytes, identified by immunohistochemical technique using specific mAbs that recognize antigenic epitopes of guinea pig T cells. Treatment with HP1/2 also resulted in a significant increase in the number of blood eosinophils, suggesting that inhibition by anti-VLA-4 mAb of eosinophil recruitment to the alveolar compartment may partially account for their accumulation in the circulation. These findings indicate that eosinophil and lymphocyte adhesion and subsequent infiltration into the guinea pig airways that follow antigen challenge are mediated by VLA-4. Furthermore, concomitant inhibition of antigen-induced bronchial hyperreactivity and of cellular infiltration by anti-VLA-4 mAb suggests a relationship between airway inflammation and modifications in the bronchopulmonary function.     

Effect of anti-IL-4 and anti-IL-5 antibodies on allergic airway hyperresponsiveness in mice

In order to study the role of IL-4 and IL-5 in allergen-induced airway hyperresponsiveness in mice, the effect of the combined administration of anti-IL-4 and anti-IL-5 monoclonal antibodies (mAbs) on IgE response, airway inflammation and airway hyperresponsiveness was studied in sensitized Balb/c mice. Three inhalations of antigen caused an increase in the number of eosinophils in bronchoalveolar lavage fluid and in airway responsiveness to acetylcholine, with a significant elevation in the serum antigen-specific IgE level. Anti-IL-4 mAb inhibited IgE production but did not affect airway eosinophilia or hyperresponsiveness. Moreover, anti-IL-5 mAb inhibited airway eosinophilia but did not affect IgE production or airway hyperresponsiveness. The combined administration of anti-IL4 and anti-IL-5 mAbs, however, inhibited IgE antibody production, airway eosinophilia and hyperresponsiveness. These results suggest that inhibitory action of IL-4 and IL-5 in combination can effectively suppress the onset of antigen-induced airway hyperresponsiveness in mice.     

IL-12, but not IFN-gamma, plays a major role in sustaining the chronic phase of colitis in IL-10-deficient mice

IL-10-deficient (IL-10(-/-)) mice develop chronic enterocolitis mediated by CD4+ Th1 cells producing IFN-gamma. Because IL-12 can promote Th1 development and IFN-gamma production, the ability of neutralizing anti-IL-12 mAb to modulate colitis in IL-10(-/-) mice was investigated. Anti-IL-12 mAb treatment completely prevented disease development in young IL-10(-/-) mice. Treatment of adult mice resulted in significant amelioration of established disease accompanied by reduced numbers of mesenteric lymph node and colonic CD4+ T cells and of mesenteric lymph node T cells spontaneously producing IFN-gamma. In contrast, anti-IFN-gamma mAb had minimal effect on disease reversal, despite a significant preventative effect in young mice. These findings suggested that IL-12 sustains colitis by supporting the expansion of differentiated Th1 cells that mediate disease independently of their IFN-gamma production. This conclusion was supported by the finding that anti-IL-12 mAb greatly diminished the ability of a limited number of CD4+ T cells expressing high levels of CD45RB from diseased IL-10(-/-) mice to expand and cause colitis in recombination-activating gene-2(-/-) recipients, while anti-IFN-gamma mAb had no effect. Furthermore, IL-12 could support pathogenic IL-10(-/-) T cells stimulated in vitro in the absence of IL-2. While these studies show that IL-12 plays an important role in sustaining activated Th1 cells during the chronic phase of disease, the inability of anti-IL-12 mAb to abolish established colitis or completely prevent disease transfer by Thl cells suggests that additional factors contribute to disease maintenance.     

A trans-acting enhancer modulates estrogen-mediated transcription of reporter genes in osteoblasts

The maturation of eosinophils in bone marrow, their migration to pulmonary tissue, and their subsequent degranulation and release of toxic granule proteins contributes to the pathophysiology observed in asthma. Interleukin-5 (IL-5) is essential for these processes to occur. Therefore, much emphasis has been placed on attempts to inhibit the production or activity of IL-5 in order to attenuate the inflammatory aspect of asthma. In this report, the immunological consequences of long-term exposure to an antibody recognizing IL-5 (TRFK-5) were studied in a murine pulmonary inflammation model. A single dose of TRFK-5 (1 mg/ kg, intraperitoneally) reversibly inhibited antigen-dependent lung eosinophilia in mice for at least 12 wk and inhibited the release of eosinophils from bone marrow for at least 8 wk. Normal responses to aerosol challenge were attained after 24 wk. In mice treated acutely with antibody (2 h before challenge), 50% inhibition of pulmonary eosinophilia occurred when 0. 06 mg/kg TRFK-5 was administered (intraperitoneally; ED50), resulting in 230 ng/ml (IC50) in serum. In mice treated with one dose of TRFK-5 (1 mg/kg) and rested before challenge, the antibody exhibited a half-life of 2.4 wk. After 18 to 19 wk, antigen challenge-induced eosinophilia was inhibited by 50% and serum levels of TRFK-5 were 25 ng/ml. TRFK-5 remaining in mice 8 wk after a single injection of TRFK-5 was sufficient to inhibit at least 50% of the eosinophilia induced in blood 3 h after injection of recombinant murine IL-5 (10 microg/kg, intravenously). To assess the biologic effect of long-term exposure of mice to antibody, several parameters of immune-cell function were measured. Throughout the extended period of activity of TRFK-5 (>/= 12 wk) there were no gross effects on antigen-dependent increases in T-cell recruitment into bronchoalveolar fluid (BALF), in IL-4 and IL-5 steady-state mRNA levels in lung tissue, or in immunoglobulin E (IgE) and IgG levels in serum. There was a small increase in IL-5 steady-state mRNA production in TRFK-5-treated mice after 2 h or 2 wk, but this was not observed at other times examined. In untreated mice, IL-5 steady-state mRNA production in response to antigen challenge decreased > 6-fold with age, although at all time points there was an increase in mRNA levels following challenge. Therefore, at later times, 25 ng/ml rather than 230 ng/ml of TRFK-5 inhibited BALF eosinophilia, probably because of reduced IL-5 levels. Twenty-four weeks after treatment with TRFK-5, when challenge-induced eosinophilia was restored, there was an excess of CD4(+) T cells in BALF from challenged mice. However, these T cells had no measurable effects on other responses to challenge, including cytokine production, B-cell accumulation, and immunoglobulin production in serum. Thus, the biologic duration of TRFK-5 was several months, and its activity was due to the presence of antibody above a therapeutic threshold rather than to any profound effect on the immune system.     

Staphylococcus aureus-induced septic arthritis and septic death is decreased in IL-4-deficient mice: role of IL-4 as promoter for bacterial growth

Lack of IL-4 has been shown to be protective in some experimental models of infectious diseases in mice such as cutaneous leishmaniasis. At the same time IL-4, together with other Th2 cytokines, including IL-10 and IL-13, is known as an anti-inflammatory cytokine with the potential to down-regulate proinflammatory cytokine production. To investigate the role of IL-4 in experimental Staphylococcus aureus-induced and T lymphocyte-mediated arthritis, IL-4-deficient C57BL/6 mice (IL-4(-/-)) and their congenic controls (IL-4(+/+)) were inoculated with a toxic shock syndrome toxin-1-producing S. aureus strain. In IL-4(+/+) mice, arthritis peaked 14 days after bacterial inoculation, whereas, at that time, IL-4(-/-) mice displayed significantly less frequent (p < 0.05) joint inflammation. Paralleling lower frequency of arthritis, IL-4-deficient mice showed a decreased bacterial burden in joints (p = 0.014) and kidneys (p = 0.029), as well as lower infection-triggered weight decrease and mortality. In vitro, IL-4 inhibited intracellular killing of S. aureus in infected macrophages, without affecting phagocytosis. This finding may explain the enhanced staphylococcal clearance observed in IL-4(-/-) mice in vivo. Our results suggest that IL-4 and IL-4-dependent Th2 responses promote septic arthritis and sepsis-related mortality by inhibition of bacterial clearance during S. aureus infection.