Developmental changes in interleukin-12-producing ability by monocytes and their relevance to allergic diseases

Repeated α-GalCer Administration Induces a Type 2 Cytokine-Biased iNKT Cell Response and Exacerbates Atopic Skin Inflammation in Vα14Tg NC/Nga Mice

We have previously shown that Vα14 TCR Tg (Vα14^Tg) NC/Nga (NC) mice contain increased numbers of double-negative (DN) invariant natural killer T (iNKT) cells that protect against spontaneous development of atopic dermatitis (AD). iNKT cells can regulate immune responses by producing various cytokines such as IFNγ and IL4 rapidly upon stimulation with α-galactosylceramide (α-GalCer), a prototypical iNKT cell agonist. However, the precise role of α-GalCer-activated iNKT cells in AD development remains unclear. Therefore, we examined whether repeated activation of iNKT cells with α-GalCer can regulate the pathogenesis of AD in Vα14^Tg NC mice. We found that Vα14^Tg NC mice injected repeatedly with α-GalCer display exacerbated AD symptoms (e.g., a higher clinical score, IgE hyperproduction, and increased numbers of splenic mast cells and neutrophils) compared with vehicle-injected Vα14^Tg NC mice. Moreover, the severity of AD pathogenesis in α-GalCer-injected Vα14^Tg NC mice correlated with increased Th2 cells but reduced Th1 and Foxp3⁺ Treg cells. Furthermore, the resulting alterations in the Th1/Th2 and Treg/Th2 balance were strongly associated with a biased expansion of type 2 cytokine-deviated iNKT cells in α-GalCer-treated Vα14^Tg NC mice. Collectively, our results have demonstrated the adverse effect of repeated α-GalCer treatment on skin inflammation mediated by type 2 immunity.

Differential maturation trajectories of innate antiviral immunity in health and atopy

BACKGROUND

The maturation of innate immune responses in health and atopy is still incompletely understood.

METHODS

We aimed to evaluate age-related trajectories of the TLR3 and TLR7/8 pathways from birth to adulthood and whether these differ between healthy and atopic individuals. Peripheral blood mononuclear cells (PBMCs) were isolated from 39 otherwise healthy, atopic and 39 non-atopic subjects, aged 0-45 years. Selected cytokines involved in antiviral responses were measured by Luminex in culture supernatants of poly(I:C)- and R848-stimulated PBMCs. The non-parametric correlation between age and cytokine expression and differences in developmental trajectories between healthy and atopic subjects were estimated. Patterns of cytokine development were identified with principal component analysis.

RESULTS

Normal innate immune maturation entails significant and progressive age-related changes in the production of IL-1β, TNF-α, MIP-1β, MCP-3, IP-10, IL-10, IL-12p70, and IFN-γ upon TLR3 and/or TLR7/8 stimulation. Individual cytokines made small contributions to the observed variability; chemokines MCP-3 and IP-10 were key contributors. The development of these pathways deviated in atopic subjects with significant differences observed in the trajectories of IL-1β, MIP-1β, and IL-10 syntheses.

CONCLUSION

TLR3 and TLR7/8 pathways mature during childhood, while atopy is associated with an abnormal maturation pattern. Suboptimal responses in Th1, inflammatory cytokine, and chemokine production may be implicated in poor antiviral immunity in atopics. Moreover, the deficient maturation of IL-10 synthesis may be implicated in the breaking of tolerance, characterizing the onset of atopic disease.

Anti-Allergic and Anti-Inflammatory Effects of Undecane on Mast Cells and Keratinocytes

The critical roles of keratinocytes and resident mast cells in skin allergy and inflammation have been highlighted in many studies. Cyclic adenosine monophosphate (cAMP), the intracellular second messenger, has also recently emerged as a target molecule in the immune reaction underlying inflammatory skin conditions. Here, we investigated whether undecane, a naturally occurring plant compound, has anti-allergic and anti-inflammatory activities on sensitized rat basophilic leukemia (RBL-2H3) mast cells and HaCaT keratinocytes and we further explored the potential involvement of the cAMP as a molecular target for undecane. We confirmed that undecane increased intracellular cAMP levels in mast cells and keratinocytes. In sensitized mast cells, undecane inhibited degranulation and the secretion of histamine and tumor necrosis factor α (TNF-α). In addition, in sensitized keratinocytes, undecane reversed the increased levels of p38 phosphorylation, nuclear factor kappaB (NF-κB) transcriptional activity and target cytokine/chemokine genes, including thymus and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC) and interleukin-8 (IL-8). These results suggest that undecane may be useful for the prevention or treatment of skin inflammatory disorders, such as atopic dermatitis, and other allergic diseases.

Dual Factors May Be Necessary for Development of Atopic March in Early Infancy

The incidence of atopic diseases, including atopic dermatitis (AD), food allergies, allergic rhinitis, and asthma, has increased in recent decades, and currently affects approximately 20% of the population. Atopic march is the development of AD in infancy and subsequent food allergies, allergic rhinitis, and asthma in later childhood. Patients with infantile eczema may develop typical symptoms of AD, allergic rhinitis, and asthma at certain ages. Some patients' symptoms persist for several years, whereas others may have resolution with aging. Development of these diseases is strongly influenced by the following two factors: skin dysfunction caused by filaggrin mutations and development of colonization of microflora in early infancy. Filaggrin mutations predisposing to asthma, allergic rhinitis, and allergic sensitization, only in the presence of AD, strongly support the role of filaggrin in the pathogenesis of AD and in subsequent progression of the atopic march. Several studies have shown that development of colonization of microflora in early infancy might affect development of allergic disease or food desensitization. Therefore, massive allergen exposure to genetic skin dysfunction in early infancy and an imbalance of microflora might be necessary for development of atopic march.

Regulation of Allergic Immune Responses by Microbial Metabolites

Emerging evidence demonstrates that the microbiota plays an essential role in shaping the development and function of host immune responses. A variety of environmental stimuli, including foods and commensals, are recognized by the host through the epithelium, acting as a physical barrier. Two allergic diseases, atopic dermatitis and food allergy, are closely linked to the microbiota, because inflammatory responses occur on the epidermal border. The microbiota generates metabolites such as short-chain fatty acids and poly-γ-glutamic acid (γPGA), which can modulate host immune responses. Here, we review how microbial metabolites can regulate allergic immune responses. Furthermore, we focus on the effect of γPGA on allergic T helper (Th) 2 responses and its therapeutic application.

Novel Therapeutic Approaches to Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common inflammatory skin diseases. The number of people affected by AD is relatively high and seems to be rising. Although mild and moderate forms of the disease can be well controlled by the use of emollients, topical corticosteroids, and topical calcineurin inhibitors, treatment of severe is still a huge challenge. The new hope is biologic drugs, magic bullets in allergy, targeted at different points of the complex pathomechanism of inflammation in AD. In this review, novel biologic therapies are discussed, including recombinant monoclonal antibodies directed against various interleukin pathways (such as IL-4, IL-13, TSLP, IL-31, and IL-12/23), on immunoglobulin E, molecules acting as T cells, B cells, etc. Of biological drugs, the most promising seems to be anti-IL-4/IL-13 therapy (dupilumab-the biological agent) and phosphodiesterase-4 inhibitor (crisaborole-a small molecule). A deep understanding of the AD pathomechanism provides a new perspective for tailor-made treatment of severe atopic dermatitis.

Postnatal Innate Immune Development: From Birth to Adulthood

It is well established that adaptive immune responses are deficient in early life, contributing to increased mortality and morbidity. The developmental trajectories of different components of innate immunity are only recently being explored. Individual molecules, cells, or pathways of innate recognition and signaling, within different compartments/anatomical sites, demonstrate variable maturation patterns. Despite some discrepancies among published data, valuable information is emerging, showing that the developmental pattern of cytokine responses during early life is age and toll-like receptor specific, and may be modified by genetic and environmental factors. Interestingly, specific environmental exposures have been linked both to innate function modifications and the occurrence of chronic inflammatory disorders, such as respiratory allergies. As these conditions are on the rise, our knowledge on innate immune development and its modulating factors needs to be expanded. Improved understanding of the sequence of events associated with disease onset and persistence will lead toward meaningful interventions. This review describes the state-of-the-art on normal postnatal innate immune ontogeny and highlights research areas that are currently explored or should be further addressed.

Altered Expression of IFN-λ2 in Allergic Airway Disorders and Identification of Its Cell Origins

This study investigated the expression levels of interferon- (IFN-) λ2 in peripheral blood and tissues. The results showed that the levels of IFN-λ2 were elevated by 17.9% and 14.2% in the plasma of allergic rhinitis (AR) and combined rhinitis with asthma (AR + AS), which was positively correlated with the level of tryptase but negatively correlated with the level of IL-10. IFN-λ2 was predominately expressed in the CD16+ cells and CD14+ cells in healthy control subjects (HC) but upregulated only in CD8+ cells of AR and in eosinophils of asthma. It was observed that approximately 6.6% and 7.0% dispersed tonsil cells and 5.8% and 0.44% dispersed lung cells are IFN-λ2+ mast cells and macrophages. Moreover, tryptase and agonist peptides of PAR-2 induced enhanced IFN-λ2 mRNA expression in A549 cells. In conclusion, the elevated levels of IFN-λ2 in the plasma of AR and AR + AS indicate that IFN-λ2 is likely to contribute to the pathogenesis of allergic airway disorders. The potential origins of the elevated plasma IFN-λ2 include mast cells, macrophages, and epithelial cells in tissues, neutrophils, monocytes, CD8+ T cells, and eosinophils in peripheral blood. Development of IFN-λ2 related therapy may help to treat or prevent allergic airway disorders.

Total IL-12 levels are increased in paediatric atopic dermatitis: correlations with age and disease severity

Alterations in the immune response play an important role in the pathogenesis of atopic dermatitis (AD). We evaluated the role of Th1/Th2 cytokine imbalance in paediatric AD and its progression towards other allergic manifestations. The levels of total interleukin (IL)-12 (p70+p40), IL-12 p70 and soluble CD30 (sCD30) were measured in paediatric patients affected by AD and in age-matched, non-atopic subjects (controls). The serum levels of total IL-12 and sCD30 were higher in patients than in controls (p=0.003 and p=0.053, respectively). Total IL-12 and sCD30 were also particularly increased in patients with severe disease. Serum levels of total IL-12 were negatively correlated with patient age (p=0.001): they were significantly higher in patients younger than 30 months, as compared to age-matched controls and to older patients and controls. Total IL-12 and sCD30 production were not significantly correlated with disease outcomes (atopic march) or with a family history of atopy. Our data show that total IL-12 levels are strongly associated with Th2 activation and severe disease in children with AD. The increased production of total IL-12 at an early age might indicate a different immune modulation and suggests the possibility of new therapeutic approaches for allergic diseases, in particular AD, early in childhood.

What’s So Special about the Developing Immune System?

The evolution of the subdiscipline of developmental immunotoxicology (DIT) as it exists today has been shaped by significant regulatory pressures as well as key scientific advances. This review considers the role played by legislation to protect children’s health, and on the emergence of immunotoxcity and developmental immunotoxicity guidelines, as well as providing some context to the need for special attention on DIT by considering the evidence that the developing immune system may have unique susceptibilities when compared to the adult immune system. Understanding the full extent of this potential has been complicated by a paucity of data detailing the development of the immune system during critical life stages as well as by the complexities of comparisons across species. Notably, there are differences between humans and nonhuman species used in toxicity testing that include specific differences relative to the timing of the development of the immune system as well as more general anatomic differences, and these differences must be factored into the interpretation of DIT studies. Likewise, understanding how the timing of the immune development impacts on various immune parameters is critical to the design of DIT studies, parameters most extensively characterized to date in young adult animals. Other factors important to DIT, which are considered in this review, are the recognition that effects other than suppression (e.g., allergy and autoimmunity) are important; the need to improve our understanding of how to assess the potential for DIT in humans; and the role that pathology has played in DIT studies in test animals. The latter point receives special emphasis in this review because pathology evaluations have been a major component of standard nonclinical toxicology studies, and could serve an important role in studies to evaluate DIT. This possibility is very consistent with recommendations to incorporate a DIT evaluation into standard developmental and reproductive toxicology (DART) protocols. The overall objective of this review is to provide a ‘snapshot’ of the current state-of-the-science of DIT. Despite significant progress, DIT is still evolving and it is our hope that this review will advance the science.

Modification of dendritic cell function as a tool to prevent and treat allergic asthma

Atopic asthma is a chronic inflammatory disease of the airways, characterized by airway hyperreactivity and mucus hypersecretion that result in intermittent airway obstruction. This chronic inflammation is the result of an aberrant Th2-mediated response to innocuous environmental proteins. The prevalence of this disease has increased dramatically in the industrialized world in the last decades. Current treatment is mainly based on pharmacological interventions, which control the disease but are not curative. Although the etiology is not completely understood, it becomes increasingly clear that dendritic cells play an important role in both the sensitization phase and maintenance of the disease. In this review, we explore the different possibilities to exploit dendritic cell vaccines in order to prevent the development of (or inhibit established) atopic asthma.

Biomarkers to assess potential developmental immunotoxicity in children

Clinical tests are readily available for assessing severe loss of immune function in children with diseases such as AIDS or primary immunodeficiency. However tests that could reliably identify subtle immune changes, as might be expected to result from exposure to developmental immunotoxic agents, are not readily available. A number of tests are described which we believe have potential applicability for epidemiological studies involving developmental immunotoxicity. Several of the tests, such as T cell receptor rearrangement excision circles (TRECs) and cytokine measurements, while highly relevant from a biological standpoint, may be precluded from use at the current time, for either technical issues or insufficient validation. Immunophenotyping and measurement of serum immunoglobulin levels, on the other hand, are well validated. Yet they may require extraordinary care in experimental design and technical performance in order to obtain data that would consistently detect subtle changes, as these tests are not generally considered highly sensitive. Quantification of the immune response to childhood vaccine, while up to the present used sparingly, may represent an excellent indicator for developmental immunotoxicity when conducted under appropriate conditions.

Dendritic cells retrovirally overexpressing IL-12 induce strong Th1 responses to inhaled antigen in the lung but fail to revert established Th2 sensitization

It has been postulated that low-level interleukin (IL)-12 production of antigen-presenting cells is associated with the risk of developing atopic asthma. To study the relationship between IL-12 production capacity of dendritic cells (DCs) and development of T helper type 2 (Th2) responses in the lung, we genetically engineered DCs to constutively overexpress bioactive IL-12. Retrovirally mediated overexpression of IL-12 in DCs strongly polarized naive ovalbumin (OVA)-specific CD4+ T cells toward Th1 effector cells in vitro. After intratracheal injection, OVA-pulsed IL-12-overexpressing DCs failed to induce Th2 responses in vivo and no longer primed mice for Th2-dependent eosinophilic airway inflammation upon OVA aerosol challenge, readily observed in mice immunized with sham-transfected, OVA-pulsed DCs. Analysis of a panel of cytokines and chemokines in the lung demonstrated that the lack of Th2 sensitization was accompanied by increased production of the Th1 cytokine interferon-gamma (IFN-gamma), chemokines induced by IFN-gamma, and the immunoregulatory cytokine IL-10. When Th2 priming was induced using OVA/alum prior to intratracheal DC administration, DCs constitutively expressing IL-12 were no longer capable of preventing eosinophilic airway inflammation and even enhanced it. These data show directly that high-level expression of IL-12 in DCs prevents the development of Th2 sensitization. Enhancing IL-12 production in DCs should be seen as a primary prevention strategy for atopic disorders. Enhancing IL-12 production in DCs is less likely to be of benefit in already Th2-sensitized individuals.