C57BL/6 mice are more susceptible to antigen-induced pulmonary eosinophilia than BALB/c mice, irrespective of systemic T helper 1/T helper 2 responses

Catching Our Breath: Updates on the Role of Dendritic Cell Subsets in Asthma

Dendritic cells (DCs), as potent antigen presenting cells, are known to play a central role in the pathophysiology of asthma. The understanding of DC biology has evolved over the years to include multiple subsets of DCs with distinct functions in the initiation and maintenance of asthma. Furthermore, asthma is increasingly recognized as a heterogeneous disease with potentially diverse underlying mechanisms. The goal of this review is to summarize the role of DCs and the various subsets therein in the pathophysiology of asthma and highlight some of the crucial animal models shaping the field today. Potential future avenues of investigation to address existing gaps in knowledge are discussed.

Thymus antibody-secreting cells possess an interferon gene signature and are preferentially expanded in young female mice

Antibody-secreting cells (ASCs) are key contributors to humoral immunity through immunoglobulin production and the potential to be long-lived. ASC persistence has been recognized in the autoimmune thymus (THY); however, only recently has this population been appreciated in healthy THY tissue. We showed that the young female THY was skewed toward higher production of ASCs relative to males. However, these differences disappeared with age. In both sexes, THY ASCs included Ki-67⁺ plasmablasts which required CD154(CD40L) signals for their propagation. Single cell RNA-sequencing revealed that THY ASCs were enriched for an interferon responsive transcriptional signature relative to those from bone marrow and spleen. Flow cytometry confirmed that THY ASCs had increased levels of Toll-like receptor 7 as well as CD69 and major histocompatibility complex class II. Overall, we identified fundamental aspects of THY ASC biology which may be leveraged for future in depth studies of this population in both health and disease.

Chebulinic acid alleviates LPS-induced inflammatory bone loss by targeting the crosstalk between reactive oxygen species/NFκB signaling in osteoblast cells

Chebulinic acid (CA), a plant ellagitannin derived from Triphala, is reported to exhibit both anti-inflammatory & anti-oxidant activity apart from anti-tumour property. However, its role in inflammatory bone loss conditions was unexplored. We hypothesized that CA may prevent the bone loss under inflammatory conditions induced by lipopolysaccharide (LPS) in 10-week-old male C57BL/6J mice. Micro-CT analysis and histomorphometric evaluations were carried out where it was found that CA significantly improved the bone micro-architectures by enhancing trabecular connectivity and strength of the bone. CA also increased the bone regeneration as examined by calcein labelling and ex-vivo mineralisation along with maintaining the bone serum markers. Further, CA ameliorated the reduction in osteoblast cell differentiation, proliferation and viability after LPS stimulation. DCFDA and Mitosox staining revealed that CA presented remarkable protective effects against LPS treatment by attenuating oxidative stress, both at cellular & mitochondrial levels. In addition, CA significantly decreased the production of pro-inflammatory cytokines, and down-regulated the phosphorylation of NFκB and IκBα, indicating that CA could attenuate the inflammatory impairment to primary osteoblast cells by suppressing the NFkB signalling pathway. Taken together, the protective role of CA against LPS-induced bone loss & inhibitory effect on total ROS levels hold promise as a potential novel therapeutic strategy for the inflammatory diseases in bones.

Pulmonary Toxicity of Polystyrene, Polypropylene, and Polyvinyl Chloride Microplastics in Mice

Globally, plastics are used in various products. Concerns regarding the human body's exposure to plastics and environmental pollution have increased with increased plastic use. Microplastics can be detected in the atmosphere, leading to potential human health risks through inhalation; however, the toxic effects of microplastic inhalation are poorly understood. In this study, we examined the pulmonary toxicity of polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC) in C57BL/6, BALB/c, and ICR mice strains. Mice were intratracheally instilled with 5 mg/kg of PS, PP, or PVC daily for two weeks. PS stimulation increased inflammatory cells in the bronchoalveolar lavage fluid (BALF) of C57BL/6 and ICR mice. Histopathological analysis of PS-instilled C57BL/6 and PP-instilled ICR mice showed inflammatory cell infiltration. PS increased the NLR family pyrin domain containing 3 (NLRP3) inflammasome components in the lung tissue of C57BL/6 and ICR mice, while PS-instilled BALB/c mice remained unchanged. PS stimulation increased inflammatory cytokines, including IL-1β and IL-6, in BALF of C57BL/6 mice. PP-instilled ICR mice showed increased NLRP3, ASC, and Caspase-1 in the lung tissue compared to the control groups and increased IL-1β levels in BALF. These results could provide baseline data for understanding the pulmonary toxicity of microplastic inhalation.

AMPK suppresses Th2 cell responses by repressing mTORC2

Allergic inflammation is a T helper 2 (Th2) cell-driven pathophysiological phenomenon, but the mechanism by which the metabolic cascade affects Th2 cell differentiation remains unclear. In this study, we investigated the roles of AMP-activated protein kinase (AMPK) and intracellular energy sensors in Th2 cell differentiation and the pathogenesis of allergic inflammation. Accordingly, T-cell-specific AMPK or Sirtuin 1 (Sirt1)-knockout mice were subjected to allergic inflammation, and their Th2 cell responses were investigated. The results demonstrated that inducing allergic inflammation in AMPK- and Sirt1-knockout mice increased Th2 cell responses and exacerbated allergic phenotypes. Furthermore, treatment with 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), an activator of AMPK, ameliorated allergic inflammation in mice. Mechanistically, our findings revealed that AMPK repressed mechanistic target of rapamycin complex 2 (mTORC2), which downregulated the expression of suppressor of cytokine signaling 5 (SOCS5) in CD4⁺ T cells. In addition, the loss of AMPK signaling reduced SOCS5 expression and increased interleukin-4-STAT6-GATA3 axis-mediated Th2 cell differentiation. Finally, the T-cell-specific deletion of Rictor, a member of mTORC2, in Sirt1^T-KO mice led to the reversal of allergic exacerbation to the level in control mice. Overall, our findings suggest that AMPK in CD4⁺ T cells inhibits the differentiation of Th2 cells by repressing mTORC2 and thus serves as a potential target for Th2 cell-associated diseases.

Age-Dependent Reduction in Asthmatic Pathology through Reprogramming of Postviral Inflammatory Responses

Asthma is a chronic disease of childhood, but for unknown reasons, disease activity sometimes subsides as children mature. In this study, we present clinical and animal model evidence suggesting that the age dependency of childhood asthma stems from an evolving host response to respiratory viral infection. Using clinical data, we show that societal suppression of respiratory virus transmission during coronavirus disease 2019 lockdown disrupted the traditional age gradient in pediatric asthma exacerbations, connecting the phenomenon of asthma remission to virus exposure. In mice, we show that asthmatic lung pathology triggered by Sendai virus (SeV) or influenza A virus is highly age-sensitive: robust in juvenile mice (4-6 wk old) but attenuated in mature mice (>3 mo old). Interestingly, allergen induction of the same asthmatic traits was less dependent on chronological age than viruses. Age-specific responses to SeV included a juvenile bias toward type 2 airway inflammation that emerged early in infection, whereas mature mice exhibited a more restricted bronchiolar distribution of infection that produced a distinct type 2 low inflammatory cytokine profile. In the basal state, aging produced changes to lung leukocyte burden, including the number and transcriptional landscape of alveolar macrophages (AMs). Importantly, depleting AMs in mature mice restored post-SeV pathology to juvenile levels. Thus, aging influences chronic outcomes of respiratory viral infection through regulation of the AM compartment and type 2 inflammatory responses to viruses. Our data provide insight into how asthma remission might develop in children.

Purified Native and Recombinant Major Alternaria alternata Allergen (Alt a 1) Induces Allergic Asthma in the Murine Model

Aeroallergens such us the spores of Alternaria alternata are described as the most important agents associated with respiratory allergies and severe asthma. Various experimental models of asthma have been developed using A. alternata extracts to study the pathogenesis of asthma, establishing the main parameters that trigger the asthmatic response. In this study, we describe a mouse model of asthma induced only by Alt a 1. To induce the allergic response, mice were challenged intranasally with the major allergen of A. alternata, Alt a 1. The presence of eosinophils in the lungs, elevated concentrations of Th2 family cytokines, lymphocyte proliferation and elevated IgE total serum levels indicated that the sensitisation and challenge with Alt a 1 induced the development of airway inflammation. Histological studies showed an eosinophilic cellular infiltrate in the lung tissue of mice instilled with Alt a 1. We demonstrate that Alt a 1 alone is capable of inducing a lung inflammatory response with an increase in IgE serum levels mimicking the allergic asthma immunoresponse when it is administered into BALB/c mice. This model will allow the evaluation of the immunoregulatory or immunotolerant capacity of several molecules that can be used in targeted immunotherapy for fungal allergic asthma.

Smooth Muscle Hypocontractility and Airway Normoresponsiveness in a Mouse Model of Pulmonary Allergic Inflammation

The contractility of airway smooth muscle (ASM) is labile. Although this feature can greatly modulate the degree of airway responsiveness in vivo, the extent by which ASM's contractility is affected by pulmonary allergic inflammation has never been compared between strains of mice exhibiting a different susceptibility to develop airway hyperresponsiveness (AHR). Herein, female C57BL/6 and BALB/c mice were treated intranasally with either saline or house dust mite (HDM) once daily for 10 consecutive days to induce pulmonary allergic inflammation. The doses of HDM were twice greater in the less susceptible C57BL/6 strain. All outcomes, including ASM contractility, were measured 24 h after the last HDM exposure. As expected, while BALB/c mice exposed to HDM became hyperresponsive to a nebulized challenge with methacholine in vivo, C57BL/6 mice remained normoresponsive. The lack of AHR in C57BL/6 mice occurred despite exhibiting more than twice as much inflammation than BALB/c mice in bronchoalveolar lavages, as well as similar degrees of inflammatory cell infiltrates within the lung tissue, goblet cell hyperplasia and thickening of the epithelium. There was no enlargement of ASM caused by HDM exposure in either strain. Unexpectedly, however, excised tracheas derived from C57BL/6 mice exposed to HDM demonstrated a decreased contractility in response to both methacholine and potassium chloride, while tracheas from BALB/c mice remained normocontractile following HDM exposure. These results suggest that the lack of AHR in C57BL/6 mice, at least in an acute model of HDM-induced pulmonary allergic inflammation, is due to an acquired ASM hypocontractility.

Understanding the complexities of SARS-CoV2 infection and its immunology: A road to immune-based therapeutics

Emerging infectious diseases always pose a threat to humans along with plant and animal life. SARS-CoV2 is the recently emerged viral infection that originated from Wuhan city of the Republic of China in December 2019. Now, it has become a pandemic. Currently, SARS-CoV2 has infected more than 27.74 million people worldwide, and taken 901,928 human lives. It was named first 'WH 1 Human CoV' and later changed to 2019 novel CoV (2019-nCoV). Scientists have established it as a zoonotic viral disease emerged from Chinese horseshoe bats, which do not develop a severe infection. For example, Rhinolophus Chinese horseshoe bats harboring severe acute respiratory syndrome-related coronavirus (SARSr-CoV) or SARSr-Rh-BatCoV appear healthy and clear the virus within 2-4 months period. The article introduces first the concept of EIDs and some past EIDs, which have affected human life. Next section discusses mysteries regarding SARS-CoV2 origin, its evolution, and human transfer. Third section describes COVID-19 clinical symptoms and factors affecting susceptibility or resistance. The fourth section introduces the SARS-CoV2 entry in the host cell, its replication, and the establishment of productive infection. Section five describes the host's immune response associated with asymptomatic, symptomatic, mild to moderate, and severe COVID-19. The subsequent seventh and eighth sections mention the immune status in COVID-19 convalescent patients and re-emergence of COVID-19 in them. Thereafter, the eighth section describes viral strategies to hijack the host antiviral immune response and generate the "cytokine storm". The ninth section describes about transgenic humane ACE2 (hACE2) receptor expressing mice to study immunity, drugs, and vaccines. The article ends with the development of different immunomodulatory and immunotherapeutics strategies, including vaccines waiting for their approval in humans as prophylaxis or treatment measures.

Dendritic Cells and T Cells, Partners in Atherogenesis and the Translating Road Ahead

Atherosclerosis is a chronic process associated with arterial inflammation, the accumulation of lipids, plaque formation in vessel walls, and thrombosis with late mortal complications such as myocardial infarction and ischemic stroke. Immune and inflammatory responses have significant effects on every phase of atherosclerosis. Increasing evidence has shown that both innate and adaptive “arms” of the immune system play important roles in regulating the progression of atherosclerosis. Accumulating evidence suggests that a unique type of innate immune cell, termed dendritic cells (DCs), play an important role as central instigators, whereas adaptive immune cells, called T lymphocytes, are crucial as active executors of the DC immunity in atherogenesis. These two important immune cell types work in pairs to establish pro-atherogenic or atheroprotective immune responses in vascular tissues. Therefore, understanding the role of DCs and T cells in atherosclerosis is extremely important. Here, in this review, we will present a complete overview, based on existing knowledge of these two cell types in the atherosclerotic microenvironment, and discuss some of the novel means of targeting DCs and T cells as therapeutic tactics for the treatment of atherosclerosis.

Interleukin-19 enhances cytokine production induced by lipopolysaccharide and inhibits cytokine production induced by polyI:C in BALB/c mice

Interleukin (IL)-19 is a cytokine of the IL-10 family. There are many reports on the involvement of IL-19 in several human diseases. There also are many reports elucidating the role of IL-19 using mouse disease models. Most reports use C57BL/6 mice, whereas few reports use BALB/c mice, in terms of the mouse disease model that the researchers used in the present study. To date, research on the role of IL-19 is diversified, yet some basic mechanisms are still unclear. In this study, we administered lipopolysaccharide (LPS), polyI:C, and CpG to BALB/c mice, measured more than 20 cytokines in the blood and compared them with that of the wild-type and IL-19-deficient (IL-19 KO) mice. LPS is associated with bacterial infection, polyI:C is associated with viral infection, and CpG is associated with both bacterial and viral infections. Among the cytokines measured, the results of experiments using LPS revealed that the production of some cytokines was suppressed in IL-19 KO mice. Interestingly, the experiments using polyI:C revealed that production of some cytokines was enhanced in IL-19 KO mice. However, the experiments using CpG have shown that the production of only one cytokine was enhanced in IL-19 KO mice. These results revealed that cytokine production in the blood was regulated by IL-19, and the type of regulation was dependent on the administered stimulant.

Formation and Glomerular Deposition of Immune Complexes in Mice Administered Human Antibodies: Evaluation of Dose, Frequency, and Biomarkers

Administration of human protein-based drugs to animals often leads to formation of antidrug antibodies (ADAs) that may form circulating immune complexes (CICs) with the dosed protein. Circulating immune complexes can activate and bind complement (cCICs), and if large amount of CICs or cCICs is formed, the clearance mechanism potentially becomes saturated, which can lead to immune complex (IC) deposition and inflammation. To obtain a better understanding of the underlying factors, including the relationship between different dose regimes on IC formation and deposition and identification of possible biomarkers of IC deposition and IC-related pathological changes in kidneys, BALB/c and C57BL/6J mice were administered with human anti-tumor necrosis factor α (aTNFα, adalimumab) or a humanized anti-TNP (aTNP) antibody for 13 weeks. Particularly, ADA, CIC, cCIC formation, IC deposition, and glomerulonephritis were observed in C57BL/6J administered with aTNFα, whereas the immunologic response was minor in BALB/c mice administered with aTNFα and in BALB/c and C57BL/6J mice administered aTNP. Changing dose levels or increasing dosing frequency of aTNFα on top of an already-established CIC and cCIC response did not lead to substantial changes in CIC, cCIC formation, or IC deposition. Finally, no association between the presence of CICs or cCIC in plasma and glomerular IC deposition and/or glomerulonephritis was observed.

Age-dependent pulmonary reactivity to house dust mite allergen: a model of adult-onset asthma?

Asthma is a heterogeneous disease differentiated by factors like allergen sensitivity, inflammation, sex, and age at onset. The mouse model is widely used to study the early-life development of allergic asthma. However, age-dependent allergen responses later in life remain relatively understudied and lack a widely accepted model. To differentiate age-dependent responses to the ubiquitous house dust mite (HDM), 3- and 9-mo-old female C57BL/6 mice were randomized into two groups each and exposed to HDM or phosphate-buffered saline (control) via intranasal instillation for sensitization and challenge phases. At 24 h after challenge, all mice underwent pulmonary function testing and methacholine challenge. Bronchoalveolar lavage fluid (BALF) was collected for assessment of cell differentials, and right lung lobes were fixed, sectioned, and stained for histopathology and immunohistochemistry. Both age groups demonstrated strong inflammatory/allergic responses to HDM exposure. However, only 9-mo-old HDM-exposed mice demonstrated significant airway hyperresponsiveness compared with age-matched controls. These HDM-exposed mice also had 1) statistically significant increases in tissue bronchiolitis, perivasculitis, and BALF neutrophilia relative to their younger counterparts and 2) significantly increased extent of immunostaining compared with all other groups. This study presents a potential model for adult-onset asthma, focusing specifically on the atopic, perimenopausal female phenotype. Our findings suggest that lung function declines with age and that the inflammatory profile of this adult subgroup is a mixed, rather than a simple, atopic, Th2 response. This model may enhance our understanding of how age influences the development of asthmic-like symptoms in older subgroups.

March1 E3 Ubiquitin Ligase Modulates Features of Allergic Asthma in an Ovalbumin-Induced Mouse Model of Lung Inflammation

Membrane-associated RING-CH-1 (March1) is a member of the March family of E3 ubiquitin ligases. March1 downregulates cell surface expression of MHC II and CD86 by targeting them to lysosomal degradation. Given the key roles of MHC class II and CD86 in T cell activation and to get further insights into the development of allergic inflammation, we asked whether March1 deficiency exacerbates or attenuates features of allergic asthma in mice. Herein, we used an acute model of allergy to compare the asthmatic phenotype of March1-deficient and -sufficient mice immunized with ovalbumin (OVA) and later challenged by intranasal instillation of OVA in the lungs. We found that eosinophilic inflammation in airways and lung tissue was similar between WT and March1^-/- allergic mice, whereas neutrophilic inflammation was significant only in March1^-/- mice. Airway hyperresponsiveness as well as levels of IFN-γ, IL-13, IL-6, and IL-10 was lower in the lungs of asthmatic March1^-/- mice compared to WT, whereas lung levels of TNF-α, IL-4, and IL-5 were not significantly different. Interestingly, in the serum, levels of total and ova-specific IgE were reduced in March1-deficient mice as compared to WT mice. Taken together, our results demonstrate a role of March1 E3 ubiquitin ligase in modulating allergic responses.

Murine Models of Allergic Asthma

Allergic asthma is a heterogeneous inflammatory lung disease affecting millions of people worldwide and with a steadily increasing incidence. Mouse models have been of utmost importance in uncovering key inflammatory cell types, cytokines, and pathways in the development and maintenance of allergic asthma. Historically, the mainstay in experimental asthma research was sensitizing rodents to the model protein antigen ovalbumin (OVA) with the pro-Th2 adjuvant aluminum hydroxide, followed by repetitive OVA exposures to the airways to initiate a Th2-skewed adaptive immune response leading to eosinophilic airway inflammation and airway hyperreactivity (AHR). In the last 5 years, OVA is often replaced by naturally occurring allergens such as house dust mite (HDM) or cockroach extracts, but the principle of first sensitizing and then repetitively challenging mice with the same antigen is unchanged. Here, we describe an often used and relevant HDM-based protocol to establish acute allergic asthma, and the methods we have developed to rapidly analyze inflammatory cell infiltration in the bronchalveolar lavage fluid by flow cytometry. Moreover, we explain the methods to restimulate T cells from lung-draining mediastinal lymph nodes with HDM to allow the measurement of cytokine secretion profiles of allergen reactive T cells.

Immunization of C57BL/6 Mice with GRA2 Combined with MPL Conferred Partial Immune Protection against Toxoplasma gondii

BACKGROUND

We have previously reported that immunization with GRA2 antigen of Toxoplasma gondii induces protective immunity in CBA/J (H2k) and BALB/c mice (H2d). We aimed to examine whether immunization of a distinct strain of rodent with recombinant dense granule antigens (GRA2) combined with monophosphorryl lipid A (MPL) adjuvant elicits protective immune response against T. gondii.

METHODS

C57BL/6 (H2b haplotype) mice were immunized with GRA2, formulated in MPL adjuvant.

RESULTS

Strong humoral response, predominantly of IgG1 subclass and cellular response, IFN-γ, was detected at three weeks post immunization. Mice immunized with GRA2 had significantly (p < 0.01) fewer brain cysts than those in the adjuvant group, upon challenge infection. Despite the production of a strong antibody response, IFN-γ production and brain cyst reduction were not significant when the immunized mice were infected four months after the immunization.

CONCLUSION

We can conclude that GRA2 immunization partially protects against T. gondii infection in C57BL/6 mice, though the potency and longevity of this antigen as a standalone vaccine may vary in distinct genetic backgrounds. This observation further emphasizes the utility of GRA2 for incorporation into a multi-antigenic vaccine against T. gondii.

Lipoxin Signaling in Murine Lung Host Responses to Cryptococcus neoformans Infection

Lipoxins (LX) are proresolving mediators that augment host defense against bacterial infection. Here, we investigated roles for LX in lung clearance of the fungal pathogen Cryptococcus neoformans (Cne). After intranasal inoculation of 5,000 CFU Cne, C57BL/6 and C.B-17 mice exhibited strain-dependent differences in Cne clearance, immunologic responses, and lipoxin A4 (LXA4) formation and receptor (ALX/FPR2) expression. Compared with C.B-17 mice, C57BL/6 lungs had increased and persistent Cne infection 14 days after inoculation, increased eosinophils, and distinct profiles of inflammatory cytokines. Relative to C.B-17 mice, bronchoalveolar lavage fluid levels of LXA4 were increased before and after infection in C57BL/6. The kinetics for 15-epi-LXA4 production were similar in both strains. Lung basal expression of the LX biosynthetic enzyme Alox12/15 (12/15-lipoxygenase) was increased in C57BL/6 mice and further increased after Cne infection. In contrast, lung basal expression of the LXA4 receptor Alx/Fpr2 was higher in C.B-17 relative to C57BL/6 mice, and after Cne infection, Alx/Fpr2 expression was significantly increased in only C.B-17 mice. Heat-killed Cne initiated lung cell generation of IFN-γ and IL-17 and was further increased in C.B-17 mice by 15-epi-LXA4. A trend toward reduced Cne clearance and IFN-γ production was observed upon in vivo administration of an ALX/FPR2 antagonist. Together, these findings provide the first evidence that alterations in cellular immunity against Cne are associated with differences in LXA4 production and receptor expression, suggesting an important role for ALX/FPR2 signaling in the regulation of pathogen-mediated inflammation and antifungal lung host defense.

Regulatory T cells in atherosclerosis: critical immune regulatory function and therapeutic potential

Atherosclerosis is a chronic inflammatory disease that is mediated by innate and adaptive immune responses. The disease is characterized by sub-endothelial accumulation and modification of lipids in the artery wall triggering an inflammatory reaction which promotes lesion progression and eventual plaque rupture, thrombus formation, and the respective clinical sequelae such as myocardial infarction or stroke. During the past decade, T-cell-mediated immune responses, especially control of pro-inflammatory signals by regulatory T cells (Tregs), have increasingly attracted the interest of experimental and clinical researchers. By suppression of T cell proliferation and secretion of anti-inflammatory cytokines, such as interleukin-10 (IL-10) and transforming growth factor-β, Tregs exert their atheroprotective properties. Atherosclerosis-prone, hyperlipidemic mice harbor systemically less Tregs compared to wild-type mice, suggesting an imbalance of immune cells which affects local and systemic inflammatory and potentially metabolic processes leading to atherogenesis. Restoring or increasing Treg frequency and enhancing their suppressive capacity by various modulations may pose a promising approach for treating inflammatory conditions such as cardiovascular diseases. In this review, we briefly summarize the immunological basics of atherosclerosis and introduce the role and contribution of different subsets of T cells. We then discuss experimental data and current knowledge pertaining to Tregs in atherosclerosis and perspectives on manipulating the adaptive immune system to alleviate atherosclerosis and cardiovascular disease.

Oral administration of heat-inactivated Lactobacillus plantarum K37 modulated airway hyperresponsiveness in ovalbumin-sensitized BALB/c mice

This study aimed to investigate the anti-allergic effects of Lactobacillus plantarum K37 (K37) on airway hyperresponsiveness (AHR) and systemic allergic responses in ovalbumin (OVA)-sensitized and -challenged BALB/c mice. Heat-inactivated K37 (10⁵, 10⁷, and 10⁹ CFU/mouse, day) were orally administered to OVA-sensitized BALB/c mice to investigate their effects on AHR, immunoglobulin (Ig) and cytokine production. The results showed that K37 dose-dependently lowered the serum levels of IgE, OVA-specific IgE and OVA-specific IgG1, ameliorated AHR induced by methacholine and suppressed eosinophil infiltration in bronchoalveolar lavage fluid (BALF). The cytokine production in spleen cells culture and BALF showed that K37 drove the immune responses toward T-helper cell type 1 (Th1) responses, elevated levels of IL-2 and IFN-γ, and reduced of IL-4, IL-5 and IL-13. K37 also improved cell infiltration in lung sections. Our results demonstrated that oral administration of K37 alleviated effectively the allergic responses invivo. Thus, K37 can be a good source material and a promising candidate for prophylactic and therapeutic treatments of allergic diseases, like asthma.

Asthma increases susceptibility to heterologous but not homologous secondary influenza

Asthma was the most common comorbidity observed among patients hospitalized with influenza A virus during the 2009 pandemic. However, little remains known about how the asthmatic phenotype influences protective immune responses against respiratory viral pathogens. Using the ovalbumin-induced allergic lung inflammation model, we found that asthmatic mice, unlike nonasthmatic mice, were highly susceptible to secondary heterologous virus challenge. While primary virus infection generated protective memory immune responses against homologous secondary virus challenge in both asthmatic and nonasthmatic mice, full protection against heterologous A/California/04/2009 (CA04) viral infection was observed only in nonasthmatic mice. Significant reductions in CA04-specific IgA, IgG, and IgM levels and in CA04-neutralizing activity of bronchoalveolar lavage fluid (BALF) was observed following secondary CA04 challenge of PR8-immunized asthmatic mice. Furthermore, transfer of immune BALF obtained from nonasthmatic, but not asthmatic, donors following secondary viral infection generated protection against CA04 in naive recipients. Nonspecific B-cell activation by CpG inoculation restored protection in PR8-immunized, CA04-challenged asthmatic mice. These results demonstrate a causal link between defective mucosal antibody responses and the heightened susceptibility of asthmatic mice to influenza infection and provide a mechanistic explanation for the observation that asthma was a major risk factor during the 2009 influenza pandemic.

IMPORTANCE

The prevalence of asthma worldwide is increasing each year. Unfortunately, there is no cure for asthma. Asthmatic individuals not only suffer from consistent wheezing and coughing but are also believed to be more prone to serious lung infections that result in bronchitis and pneumonia. However, little is known about the influence of asthma on host mucosal immunity. Here we show that antibody responses during secondary heterologous influenza infections are suboptimal and that this is responsible for the increased mortality in asthmatic mice from viral infections. Understanding the mechanism of increased susceptibility will aid in developing new antiviral therapies for asthmatic patients.

Immunomodulatory Activity of Lactococcus lactis A17 from Taiwan Fermented Cabbage in OVA-Sensitized BALB/c Mice

From fermented Taiwan foods, we have isolated numerous lactic acid bacteria (LAB) of plant origin and investigated their biological activities. This study aimed to investigate the immunomodulatory effect and mechanism of Lactococcus lactis A17 (A17), isolated from Taiwan fermented cabbage, on ovalbumin (OVA)-sensitized mice. Human peripheral blood mononuclear cells were used to verify immune responses of A17 by IFN-γ production. Live (A17-A) and heat-killed A17 (A17-H) were orally administered to OVA-sensitized BALB/c mice to investigate their effects on immunoglobulin (Ig) and cytokine production. The mRNA expression of Toll-like receptors (TLR) and nucleotide binding oligomerization domain (NOD)-like protein receptors in spleen cells was analyzed by real-time RT-PCR. Both live and heat-killed A17 modulate OVA-induced allergic effects. B-cell response was modulated by diminishing IgE production and raising OVA-specific IgG2a production, while T-cell response was modulated by increasing IFN-γ production and decreasing IL-4 production. The mRNA expression of NOD-1, NOD-2, and TLR-4 was down-regulated by A17 as well. This is the first report to describe a naïve Lactococcus lactis A17 strain as a promising candidate for prophylactic and therapeutic treatments of allergic diseases via oral administration. Our results suggest the ameliorative effects of A17 may be caused by modulating NOD-1 NOD-2, and TLR-4 expression.

Oral Nigella sativa oil ameliorates ovalbumin-induced bronchial asthma in mice

Nigella sativa oil (NSO) is used in folk medicine as a therapy for many diseases including bronchial asthma. We investigated the possible modulating effects of NSO on asthma-like phenotypes in a mouse model of bronchial asthma. BALB/c mice were actively sensitized by intraperitoneal injections of 50 μg ovalbumin (OVA) with 1mg alum on days 0 and 12. Starting on day 22, they were exposed to OVA (1% (w/v), in sterile physiological saline) for 30 min, three times every 4th day. Negative control animals were exposed to saline in a similar manner. NSO was administered orally for 31 day from day 0 to day 30. On the day of sensitization and challenge, NSO was given 30 min before the treatment. Airway function, number of inflammatory cells in bronchoalveolar lavage fluid (BALF), levels of interleukin (IL)-4, IL-5, IL-13 and interferon (IFN)-γ in BALF, serum levels of total IgE, OVA-specific IgE, IgG1 and IgG2a, and histopathological examination of lung tissues were investigated. Oral treatment with NSO showed significant decrease in airway hyperresponsiveness, the number of total leukocytes, macrophages and eosinophils, levels of IL-4, IL-5 and IL-13 in BALF, serum levels of total IgE, OVA-specific IgE and IgG1, and significant increase in BALF level of IFN-γ and serum level of OVA-specific IgG2a, indicating restoration of local Th1/Th2 balance. Furthermore, it significantly abrogated the histopathological changes of the lungs, as the images were nearly normal. These results suggest that the treatment with oral NSO could be a promising treatment for bronchial asthma in humans.

Genetic variation determines mast cell functions in experimental asthma

Mast cell-deficient mice are a key for investigating the function of mast cells in health and disease. Allergic airway disease induced as a Th2-type immune response in mice is employed as a model to unravel the mechanisms underlying inception and progression of human allergic asthma. Previous work done in mast cell-deficient mouse strains that otherwise typically mount Th1-dominated immune responses revealed contradictory results as to whether mast cells contribute to the development of airway hyperresponsiveness and airway inflammation. However, a major contribution of mast cells was shown using adjuvant-free protocols to achieve sensitization. The identification of a traceable genetic polymorphism closely linked to the Kit(W-sh) allele allowed us to generate congenic mast cell-deficient mice on a Th2-prone BALB/c background, termed C.B6-Kit(W-sh). In accordance with the expectations, C.B6-Kit(W-sh) mice do not develop IgE- and mast cell-dependent passive cutaneous anaphylaxis. Yet, unexpectedly, C.B6-Kit(W-sh) mice develop full-blown airway inflammation, airway hyperresponsiveness, and mucus production despite the absence of mast cells. Thus, our findings demonstrate a major influence of genetic background on the contribution of mast cells in an important disease model and introduce a novel strain of mast cell-deficient mice.

Itk: the rheostat of the T cell response

The nonreceptor tyrosine kinase Itk plays a key role in TCR-initiated signaling that directly and significantly affects the regulation of PLCγ1 and the consequent mobilization of Ca²⁺. Itk also participates in the regulation of cytoskeletal reorganization as well as cellular adhesion, which is necessary for a productive T cell response. The functional cellular outcome of these molecular regulations by Itk renders it an important mediator of T cell development and differentiation. This paper encompasses the structure of Itk, the signaling parameters leading to Itk activation, and Itk effects on molecular pathways resulting in functional cellular outcomes. The incorporation of these factors persuades one to believe that Itk serves as a modulator, or rheostat, critically fine-tuning the T cell response.

Allogeneic mesenchymal stem cells prevent allergic airway inflammation by inducing murine regulatory T cells

BACKGROUND

Adult bone marrow-derived mesenchymal stem cells (MSC) possess potent immune modulatory effects which support their possible use as a therapy for immune-mediated disease. MSC induce regulatory T cells (T(reg)) in vitro although the in vivo relevance of this is not clear.

OBJECTIVE

This study addressed the hypothesis that adult bone marrow derived-MSC would prevent the pathology associated with allergen-driven airway inflammation, and sought to define the effector mechanism.

METHODS

The influence of allogeneic MSC was examined in a model system where T(reg) induction is essential to prevent pathology. This was tested using a combination of a model of ovalbumin-driven inflammation with allogeneic MSC cell therapy.

RESULTS

Systemic administration of allogeneic MSC protected the airways from allergen-induced pathology, reducing airway inflammation and allergen-specific IgE. MSC were not globally suppressive but induced CD4(+) FoxP3(+) T cells and modulated cell-mediated responses at a local and systemic level, decreasing IL-4 but increasing IL-10 in bronchial fluid and from allergen re-stimulated splenocytes. Moderate dose cyclophosphamide protocols were used to differentially ablate T(reg) responses; under these conditions the major beneficial effect of MSC therapy was lost, suggesting induction of T(reg) as the key mechanism of action by MSC in this model. In spite of the elimination of T(reg) , a significant reduction in airway eosinophilia persisted in those treated with MSC.

CONCLUSION

These data demonstrate that MSC induce T(reg) in vivo and reduce allergen-driven pathology. Multiple T(reg) dependent and independent mechanisms of therapeutic action are employed by MSC.

New production of eosinophils and the corresponding TH1/TH2 balance in the lungs after allergen exposure in BALB/c and C57BL/6 mice

Allergic asthma is associated with eosinophilic inflammation in the airways. Animal models commonly used to elucidate allergic inflammation mechanisms include BALB/c and C57BL/6 mice. Our aim was to evaluate lung eosinophilia and the corresponding Th1/Th2 balance in the two strains after allergen exposure. BALB/c and C57BL/6 mice were subjected to ovalbumin-induced allergic airway inflammation using BrdU to label newly produced cells. The numbers of new eosinophils were evaluated by differential cell count and immunocytochemistry (MBP+BrdU+). Proliferation rate of lung eosinophils was measured by analysis of CD45+CCR3+BrdU+ cells by FACS. Distribution of newly produced eosinophils in the lung and the Th1/Th2 (CD4+T-bet+/CD4+GATA-3+) balance was evaluated by immunohistochemistry. Allergen challenge with ovalbumin induced comparable eosinophilia in bone marrow (BM), blood and lung tissue in both strains of mice compared to phosphate-buffered saline controls, which was confirmed by immunocytochemistry. There was a small increase in the number of lung MBP+BrdU(-) eosinophils in C57BL/6 mice compared to BALB/c mice, which suggests a basal increase in this strain following sensitization. While there was no difference in eosinophilic proliferation in the lung, the distribution of the newly produced eosinophils differs between the two strains. BALB/c mice showed staining primarily around vessels and airways, whereas C57BL/6 mice showed a more even distribution in the lung tissue. No difference in the Th1/Th2 balance was observed between two strains. This study shows that there is a difference in the distribution of eosinophils in the lung between the C57BL/6 and BALB/c mice, but no difference in eosinophil production or Th1/Th2 balance.

Attenuated Bordetella pertussis vaccine strain BPZE1 modulates allergen-induced immunity and prevents allergic pulmonary pathology in a murine model

BACKGROUND

Virulent Bordetella pertussis, the causative agent of whooping cough, exacerbates allergic airway inflammation in a murine model of ovalbumin (OVA) sensitization. A live genetically attenuated B. pertussis mucosal vaccine, BPZE1, has been developed that evokes full protection against virulent challenge in mice but the effect of this attenuated strain on the development of allergic responses is unknown.

OBJECTIVE

To assess the influence of attenuated B. pertussis BPZE1 on OVA priming in a murine model of allergic airway inflammation.

METHODS

Mice were challenged with virulent or attenuated strains of B. pertussis, and sensitized to allergen (OVA) at the peak of bacterial carriage. Subsequently, airway pathology, local inflammation and OVA-specific immunity were examined.

RESULTS

In contrast to virulent B. pertussis, live BPZE1 did not exacerbate but reduced the airway pathology associated with allergen sensitization. BPZE1 immunization before allergen sensitization did not have an adjuvant effect on allergen specific IgE but resulted in a statistically significant decrease in airway inflammation in tissue and bronchoalveolar lavage fluid. BPZE1 significantly reduced the levels of OVA-driven IL-4, IL-5 and IL-13 but induced a significant increase in IFN-gamma in response to OVA re-stimulation.

CONCLUSIONS

These data demonstrate that, unlike virulent strains, the candidate attenuated B. pertussis vaccine BPZE1 does not exacerbate allergen-driven airway pathology. BPZE1 may represent an attractive T-helper type 1 promoting vaccine candidate for eradication of whooping cough that is unlikely to promote atopic disease.

Understanding asthma using animal models

Asthma is a complex syndrome with many clinical phenotypes in children and adults. Despite the rapidly increasing prevalence, clinical investigation and epidemiological studies of asthma, the successful introduction of new drugs has been limited due to the different disease phenotypes and ethical issues. Mouse models of asthma replicate many of the features of human asthma, including airway hyperreactivity, and airway inflammation. Therefore, examination of disease mechanisms in mice has been used to elucidate asthma pathology and to identify and evaluate new therapeutic agents. In this article, we discuss the various animal models of asthma with a focus on mouse strains, allergens, protocols, and outcome measurements.

Enhancement of ovalbumin-induced pulmonary eosinophilia by intranasal administration of alpha1-proteinase inhibitor type 2 antisense oligonucleotides

To identify asthma-susceptibility genes, we did proteome analyses of the lung from control and ovalbumin-sensitized BALB/c mice. Among the 6 up-regulated proteins is alpha(1)-protease inhibitor (alpha(1)-PI) type 2, which is a member of the serine protease inhibitor superfamily of protease inhibitors that participate in a variety of physiological functions, including extracellular matrix remodeling and inflammation. The up-regulated expression of alpha(1)-PI type 2 was confirmed by real-time PCR. Then we examined mRNA expression of five members of the alpha(1)-PI family genes (alpha(1)-PI types 1-5) in several organs of BALB/c mice and found that in addition to the liver, all the organs tested also expressed different isoforms of alpha(1)-PI in a tissue-specific manner, albeit to a lesser extent compared with the liver. When a similar study was performed with C57BL/6 mice, which have been shown to be more susceptible to ovalbumin-induced asthma than BALB/c mice, a pair of remarkable differences between the mouse strains were revealed: (1) the magnitude of alpha(1)-PI type 2 mRNA in all the organs was much higher in BALB/c than in C57BL/6 mice and (2) alpha(1)-PI type 2 is the only isoform expressed in the lung of BALB/c, but not of C57BL/c mice. Using the antisense oligonucleotide technology to specifically down-regulate expression of alpha(1)-PI type 2, we demonstrated that pulmonary infiltration of eosinophils was significantly increased by intranasal administration of alpha(1)-PI type 2 antisense oligonucleotides in OVA-sensitized mice, suggesting that alpha(1)-PI type 2 may suppress the progress of asthma, probably by acting on neutrophil elastase, which can produce many of the pathological features of asthma.

The distinctive effects of acute and chronic psychological stress on airway inflammation in a murine model of allergic asthma

BACKGROUND

Psychological stress has long been recognized to be associated with asthma symptoms. There appear to be individual differences in the susceptibility to even the same kind of stress, and furthermore, stress responses are different between the types of the stress, acute and chronic, even in the same person. However, the mechanisms linking stress to asthma are not well defined. Psychological stress upregulates the expression of endogenous opioids. The opioids stimulate the hypothalamus-pituitary-adrenal axis and sympathetic and adrenomedullary system, through the activation of mu-opioid receptor (MOR) to release stress hormones, such as cortisol and catecholamines, respectively. These hormones can modulate immune responses via the induction of Th1 immunity.

METHODS

Female BALB/c and C57BL/6, wild and MOR-deficient, mice sensitized with ovalbumin (OVA) were exposed to OVA with or without either acute or chronic restraint stress. Airway inflammation was evaluated by the measurement of the number of inflammatory cells and cytokine contents in bronchoalveolar lavage fluids.

RESULTS

In BALB/c mice, but not in C57BL/6 mice, the number of total cells, eosinophils and lymphocytes in the acute stress group were significantly decreased compared with those in the non-acute stress group. In contrast, chronic stress significantly increased the cell numbers and the contents of IL-4 and IL-5 in both mouse strains. Furthermore, these exacerbations were abolished in MOR-deficient mice.

CONCLUSIONS

These results suggest that acute stress modifies the allergic airway responses distinctively depending on the genetic background, and MOR is involved in the chronic psychological stress-induced exacerbation of allergic airway inflammation.

Genetic background determines susceptibility to experimental immune-mediated blepharoconjunctivitis: Comparison of Balb/c and C57BL/6 mice

Balb/c and C57BL/6 mice have been reported to be biased towards Th2 and Th1 immune responses, respectively. We investigated which strain is more susceptible to the development of experimental immune-mediated blepharoconjunctivitis (EC), which is predominantly mediated by Th2 immune responses. EC was induced by three different methods in Balb/c and C57BL/6 mice using ragweed (RW) as the antigen. The mice were thus either actively immunized with RW, passively immunized by transfer of RW-primed T cells, or passively immunized by transfer of RW-specific IgE, followed by RW challenge in eye drops. Twenty-four hours after the challenge, conjunctivas, sera and spleens were harvested for histological analysis, measurement of serum IgE and assessment of cellular immune responses, respectively. The responses of the Balb/c and C57BL/6 mice were compared. In addition, to assess the involvement of IFN-gamma in the development of EC in the two strains, IFN-gamma knockout (GKO) mice of the two strains were actively immunized and evaluated as above. Regardless of the method of induction, EC, as determined by the degree of eosinophil infiltration into the conjunctiva, was more severe in Balb/c mice than in C57BL/6 mice. Moreover, more IgE was produced by actively immunized Balb/c mice than C57BL/6 mice and RW-primed splenocytes from Balb/c mice produced more IL-4 but less IFN-gamma than those from C57BL/6 mice. EC could be induced in the GKO mice of both strains. However, when their EC was compared to that in WT mice, significantly less infiltration of eosinophils was noted in the Balb/c GKO mice. Taken together, Balb/c mice are more susceptible to EC than C57BL/6 mice and this higher susceptibility might be related to the Th2 immune response bias of Balb/c mice. Furthermore, the involvement of endogenous IFN-gamma in the development of EC in these two strains differs.

T cell-induced inflammation of the small and large intestine in immunodeficient mice

It is well known that transfer of CD4+CD45RBhigh (naïve) T cells into syngeneic lymphocyte-deficient mice induces chronic colitis. However, no studies have reported the presence of small bowel inflammation in this T cell-dependent model. Therefore, the objective of this study was to evaluate and compare small and large bowel inflammation induced by transfer of naïve T cells into two different immunodeficient recipient mice. T and B cell-deficient recombinase activating gene 1-deficient [RAG knockout (KO)] and T cell-deficient T cell receptor-beta x T cell receptor-delta double-deficient (TCR KO) mice were reconstituted with wild-type naïve T cells and observed for signs of disease. We found that reconstituted RAG KO mice developed moderate to severe colitis and inflammation of the entire small intestine at 6-8 wk after T cell transfer. Adoptive transfer of naïve T cells into TCR KO mice induced a milder form of chronic colitis and small bowel inflammation that was confined primarily to the duodenum at 10-12 wk after T cell transfer. T helper cell 1 and macrophage-derived proinflammatory cytokine mRNA levels correlated well with the localization and severity of the chronic large and small bowel inflammation. In addition, we observed comparable homing and expansion of donor lymphocytes in the gut and secondary lymphoid tissues of both recipients. Taken together, our data demonstrate that transfer of naïve T cells into immunodeficient recipient mice induces both chronic small and large bowel inflammation and that the presence of B cells in the TCR KO recipients may play a role in regulating chronic intestinal inflammation.

Whole-cell pertussis vaccine protects against Bordetella pertussis exacerbation of allergic asthma

The prevalence of asthma and allergic disease has increased in many countries and there has been speculation that immunization promotes allergic sensitization. Bordetella pertussis infection exacerbates allergic asthmatic responses. We investigated whether whole-cell pertussis vaccine (Pw) enhanced or prevented B. pertussis induced exacerbation of allergic asthma. Groups of mice were immunized with Pw, infected with B. pertussis and/or sensitized to ovalbumin. Immunological, pathological and physiological changes were measured to assess the impact of Pw immunization on immune deviation and airway function. Pw immunization modulated ovalbumin-specific serum IgE production, and reduced local and systemic IL-13 and other cytokine responses to sensitizing allergen. Histopathological examination revealed Pw immunization reduced the severity of airway pathology and decreased bronchial hyperreactivity to methacholine exposure. Pw does not enhance airway IL-13 and consequently does not enhance but protects against the exacerbation of allergic responses. We find no evidence of Pw contributing to allergic asthma, but rather provide evidence of a mechanism whereby whole-cell pertussis vaccination has a protective role.

Mice vaccinated with allergen-pulsed myeloid dendritic cells are not protected from developing allergen-induced Th2 responses

BACKGROUND

Dendritic cells (DC) play a decisive role in the induction of allergen-induced Th1 and Th2 responses. Since the induction of allergen-specific Th1 responses has shown to inhibit allergen-induced Th2-type inflammation, in this study we investigated whether manipulated myeloid-derived DC pulsed with the specific allergen would predominantly induce allergen-specific Th1 responses thereby reducing the development of Th2 responses.

METHODS

Murine bone marrow (BM)-DC were generated and pulsed with ovalbumin (OVA) and CpG oligodeoxynucleotides (CpG-ODN). Langerhans cells (LC) were also isolated and pulsed in vitro with OVA. Subsequently, mice were vaccinated intravenously with either CpG/OVA-pulsed BM-DC or OVA-pulsed LC, and the protocol to induce OVA-specific Th2 responses using OVA/alum sensitization was initiated. Airway inflammation and OVA-specific serum antibody levels were evaluated 6 days after the intranasal challenge with OVA.

RESULTS

The application ofCpG/OVA-pulsed BM-DC was unable to reduce airway eosinophilia and inflammation in OVA/alum-immunized mice. OVA-specific IgG1 or IgE serum levels were also not reduced. The experiments using LC pulsed with OVA yielded similar results. However, mice vaccinated with CpG/OVA-pulsed BM-DC had greatly enhanced levels of serum OVA-specific IgG2a, suggesting the induction of allergen-specific Th1 responses in vivo. Moreover, allergen-induced mast cell degranulation was decreased using this approach.

CONCLUSIONS

Taken together, our results demonstrated that the vaccination with OVA-pulsed BM-DC matured with CpG-ODN or OVA-pulsed LC did not result in a reduction in allergen-specific Th2 responses in a murine model of severe atopic asthma. Other DC-based vaccination strategies should be evaluated in order to prevent the development of allergic disorders.

Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. I. Introduction, objectives, and experimental plan

This subchronic (6-mo) inhalation study of the effects of concentrated ambient air fine particulate matter (PM2.5) in normal mice (C57) and a murine model of humans with an advanced level of aortic plaque (ApoE-/- or ApoE-/- LDLr-/-) was designed to determine the presence and extent of a variety of health-related responses. The animals were exposed for 6 h/day, 5 day/wk during the spring and summer of 2003 to concentrations that were elevated 10-fold in Tuxedo, NY, a regional background site that is upwind and approximately 50 km west-northwest of New York City. The average PM2.5 concentration during exposure was 110 microgram/m3, and the long-term average was 19.7 microg/m3. There were substantial daily variations in concentration, and we sought evidence both for the influence of peak exposures on acute responses and for the cumulative effects of the prolonged series of exposures. Acute responses were characterized in terms of: (1) short-term electrocardiographic (EKG), core body temperature, and physical activity differences between PM and sham-exposed mice; and (2) in vitro toxicity of a simultaneously collected PM2.5 sample to lung epithelial cells. Cumulative responses to PM2.5 were characterized in terms of changes in heart rate, heart-rate variability, heart-rate variance, aortic plaque density, genetic marker expression, and brain cell distributions. There were no significant changes in the normal mice. The nature and extent of the exposure-related responses that were seen in the ApoE-/- as well as ApoE-/- LDLr-/- mice are described in the articles that follow in this special issue of Inhalation Toxicology.

Host-specific differences in the physiology of acid secretion related to prostaglandins may play a role in gastric inflammation and injury

Immune mediators are involved in strain-specific manifestations of Helicobacter pylori infection, and the type of immune response is associated with production of PGE(2), which in turn influences gastric acid secretion. Acid secretion plays a pivotal role, not only in the pattern of H. pylori-induced gastritis and its consequences, but also in nonsteroidal anti-inflammatory drug (NSAID)-induced gastropathies. Mice and their transgenic modifications are widely used in Helicobacter and eicosanoid research. Using [(14)C]aminopyrine accumulation and pylorus ligation, we aimed to study acid secretion in gastric gland preparations from the commonly used strains of BALB/c and C57BL/6 mice. We found that PGE(2) does not inhibit acid secretion in gastric glands from C57BL/6 mice, in contrast to the expected antisecretory effect of PGE(2) observed in BALB/c mice. In BALB/c mice the effect of histamine and carbachol was reduced by PGE(2), whereas in C57BL/6 mice dose-response curves to these secretagogues were not affected. EP(3) receptors are not involved in acid secretion in C57BL/6 mice, as confirmed by significantly lower expression of mRNA for the EP(3) receptor. These contrary findings are important to the interpretation of the antisecretory role of eicosanoids in BALB/c and C57BL/6 mouse strains and the involvement of prostanoids in the etiology of Helicobacter-induced inflammation and NSAID-induced gastropathies. We propose that the lack of antisecretory effect of PGE(2) observed in C57BL/6 mice could reflect the extent of Helicobacter-induced inflammation and status of acid secretion in response to anti-inflammatory drugs.

Exposure of adult mice to environmental tobacco smoke fails to enhance the immune response to inhaled antigen

Epidemiologic evidence supports a role for environmental tobacco smoke (ETS) in the occurrence and severity of allergies/asthma. However, neither the precise combination of ETS and allergen exposure nor the mechanism (or mechanisms) by which these factors interact and contribute to asthma induction is known. Animal model studies have failed to establish a convincing relationship between ETS exposure and asthma induction, perhaps because of methodological inadequacies. Here, we tested the hypothesis that ETS inhalation would provoke an asthmatic response by overcoming normal airway tolerance to inhaled antigens. Our protocol combined daily ETS exposure with nose-only sensitization to ovalbumin. Three strains of mice were tested, each with a different level of susceptibility to airway hypersensitivity. Immunological responses were assessed by immunoglobulin production. Airway inflammation was assessed by bronchoalveolar lavage differentials and lung histopathology. Airway hyperresponsiveness was determined by methacholine challenge. The mice produced ovalbumin-specific antibodies following ovalbumin exposure in a strain-dependent manner. Only the A/J mice produced detectable levels of ovalbumin-specific immunoglobulin (Ig) E. Both A/J and BALB/c mice produced ovalbumin-specific IgG1 antibodies. The C57Bl/6 mice did not produce detectable levels of antibodies. The A/J mice also exhibited airway inflammation following ovalbumin exposure. Neither the C57Bl/6 nor the BALB/c mice exhibited signs of airway inflammation. Exposure to ETS failed to enhance ovalbumin-specific antibody production, airway inflammation, or hyperresponsiveness. Together these results indicate that ETS exposure accompanied by nose-only allergen sensitization fails to overcome aerosol tolerance in adult mice.

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 ED50 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.

Prior Bordetella pertussis infection modulates allergen priming and the severity of airway pathology in a murine model of allergic asthma

BACKGROUND

It has been proposed that T helper (Th)2-driven immune deviation in early life can be countered by Th1 inducing childhood infections and that such counter-regulation can protect against allergic asthma.

OBJECTIVE

To test whether Th1-inducing infection with Bordetella pertussis protects against allergic asthma using well-characterized murine models.

METHODS

Groups of mice were sensitized to ovalbumin (OVA) in the presence or absence of B. pertussis, a well-characterized Th1 inducing respiratory infection. Immunological, pathological and physiological parameters were measured to assess the impact of infection on immune deviation and airway function.

RESULTS

We demonstrate that OVA sensitization does not affect the development of B. pertussis-specific immune responses dominated by IgG2a and IFN-gamma and does not impair Th1-mediated clearance of airway infection. In contrast, B. pertussis infection at the time of sensitization modulated the response to OVA and significantly reduced total serum and OVA-specific IgE. The pattern of cytokine responses, in particular OVA-specific IL-5 responses in the spleen was also modulated. However, B. pertussis did not cause global suppression as IL-10 and IL-13 levels were enhanced in OVA-stimulated spleen cell cultures and in lavage fluid from infected co-sensitized mice. Histopathological examination revealed that B. pertussis infection prior to OVA sensitization resulted in increased inflammation of bronchiolar walls with accompanying hyperplasia and mucous metaplasia of lining epithelia. These pathological changes were accompanied by increased bronchial hyper-reactivity to methacholine exposure.

CONCLUSION

Contrary to the above premise, a Th1 response induced by a common childhood infection does not protect against bronchial hyper-reactivity, but rather exacerbates the allergic asthmatic response, despite modulation of immune mediators.

Asthma: mechanisms of disease persistence and progression

When asthma is diagnosed, eosinophilic inflammation and airway remodeling are established in the bronchial airways and can no longer be separated as cause and effect because both processes contribute to persistence and progression of disease, despite anti-inflammatory therapy. Th2 cells are continually active in the airways, even when disease is quiescent. IL-13 is the key effector cytokine in asthma and stimulates airway fibrosis through the action of matrix metalloproteinases on TGF-beta and promotes epithelial damage, mucus production, and eosinophilia. The production of IL-13 and other Th2 cytokines by non-T cells augments the inflammatory response. Inflammation is amplified by local responses of the epithelium, smooth muscle, and fibroblasts through the production of chemokines, cytokines, and proteases. Injured cells produce adenosine that enhances IL-13 production. We review human and animal data detailing the cellular and molecular interactions in established allergic asthma that promote persistent disease, amplify inflammation, and, in turn, cause disease progression.

Asian pear pectin administration during presensitization inhibits allergic response to ovalbumin in BALB/c mice

OBJECTIVE

A type of respiratory disorder resembling some aspects of human allergic asthma can be induced in mice using ovalbumin. The factors that influence the etiology of asthma are poorly understood even though cytokines are known to play a pivotal role. The purpose of this study was to test the hypothesis whether an administration of Asian pear pectin during presensitization could suppress allergic response to ovalbumin in BALB/c mice.

DESIGN

High-dose (100 microg) of pectin-sol was used and values were compared to those from the control. Ovalbumin and aluminum hydroxide were utilized for sensitization while ovalbumin aerosol was used for provocation 2 weeks later. The bronchoalveolar lavage (BAL) and assessment of tracheal smooth muscle responsiveness to electrical field stimulation or acetylcholine were performed 1 day after ovalbumin provocation. Two main cytokines of interferon (IFN)-gamma and interleukin (IL)-5, and serum immunoglobulin E (IgE) were assayed.

SETTINGS

Laboratory of the Chosun University Medical School

SUBJECT

Male BALB/c mice

RESULTS

Antigen dose of 5 microg for sensitization generated TH1 type cytokines in the lungs with a high level of IFN-gamma and a low level of IL-5. In contrast, TH2 type cytokines were produced in splenocytes including a high level of IL-5 and a low level of IFN-gamma. Asian pear pectin-sol administration during presensitization significantly inhibited (p < 0.05) sensitivity of airway smooth muscle to electrical field stimulation and acetylcholine. Further, IFN-gamma production significantly decreased (p < 0.05) in BAL fluids while it significantly increased (p < 0.05) in splenic cells. On the other hand, IL-5 production significantly increased (p < 0.05) in BAL fluids while it was a significant decrease (p < 0.05) in splenic cells. For the histopathologic changes in the lung, pear pectin-sol recovered ovalbumin (OVA)-induced abnormal signs to an almost normal state. As a correlate, IgE production significantly decreased (p < 0.05) in pectin-sol-treated animals compared to the control.

CONCLUSIONS

It is possible from these data that BALB/c mice have different susceptibilities to different doses of OVA regulated by pulmonary TH1 and TH2 type cytokines, independent of splenic TH1 and TH2 type cytokines production. These results also indicate that administration of Asian pear pectin-sol in presensitized mice suppresses allergic asthmatic reaction.

Airway remodeling of murine chronic antigen exposure model

Airway remodeling is one of the most important features of bronchial asthma. However, there are few studies that have used repeated antigen exposure in murine models. We designed a murine chronic antigen exposure model necessary for studying airway remodeling. Two different strains of mice, BALB/c mice and C57BL/6 mice, were sensitized and challenged for 3-7 weeks with ovalbumin (OVA). Bronchoalveolar lavage (BAL) and histology study were conducted in each phase. Morphometry was performed, and the epithelial area ratio (Ae ratio) and subepithelial area ratio (As ratio) were calculated. The Ae ratio and As ratio of BALB/c mice were significantly increased in sensitized mice compared with non-sensitized mice at 3 and 5 weeks, but not at 7 weeks. In C57BL/6 mice, the Ae ratio showed no significant changes, whereas the As ratio maintained high from 3 to 7 weeks. This thickening of the subepithelial layer consisted of collagen fibers with elastica van-Gieson (EVG) stain. Lymphocytes of the BAL showed a significant increase at 3 and 7 weeks in C57BL/6 mice, but not in BALB/c mice. A murine chronic OVA exposure model in C57BL/6 mice revealed subepithelial layer thickening consisting of collagen fibers and increased lymphocytes until 7 weeks. C57BL/6 mice are useful to elucidate the mechanism of airway remodeling.

Resistance and susceptibility to filarial infection with Litomosoides sigmodontis are associated with early differences in parasite development and in localized immune reactions

In order to understand natural resistance to filariasis, we compared Litomosoides sigmodontis primary infection of C57BL/6 mice, which eliminate the worms before patency, and BALB/c mice, in which worms complete their development and produce microfilariae. Our analysis over the first month of infection monitoredmigration of the infective larvae from the lymph nodes to the pleural cavity, where the worms settle. Although immune responses from the mouse strains differed from the outset, the duration of lymphatic migration (4 days) and filarial recovery rates were similar, thus confirming that the proportion of larvae that develop in the host species upon infection is not influenced by host genetic variability. The majority of worms reached the adult stage in both mouse strains; however, worm growth and molting were retarded in resistant C57BL/6 mice. Surprisingly, the only immune responses detected at 60 h postinfection occurred in the susceptible mice and only upon stimulation of cells from lymph nodes draining the inoculation site with infective larva extract: massive production of interleukin-6 (IL-6) and IL-5 (the latter cytokine was previously suspected to have an effect on L. sigmodontis growth). However, between days 10 and 30 postinfection, extraordinarily high levels of type 1 and type 2 cytokines and expansion of pleural leukocyte infiltration were seen in the resistant C57BL/6 mice, explaining the destruction of worms later. Our results suggest that events early in the infection determine susceptibility or resistance to subsequent microfilarial production and a parasite strategy to use specific immune responses to its own benefit.