The role of iNKT cells on the phenotypes of allergic airways in a mouse model

Early-life interactions between the microbiota and immune system: impact on immune system development and atopic disease

Prenatal and early postnatal life represent key periods of immune system development. In addition to genetics and host biology, environment has a large and irreversible role in the immune maturation and health of an infant. One key player in this process is the gut microbiota, a diverse community of microorganisms that colonizes the human intestine. The diet, environment and medical interventions experienced by an infant determine the establishment and progression of the intestinal microbiota, which interacts with and trains the developing immune system. Several chronic immune-mediated diseases have been linked to an altered gut microbiota during early infancy. The recent rise in allergic disease incidence has been explained by the 'hygiene hypothesis', which states that societal changes in developed countries have led to reduced early-life microbial exposures, negatively impacting immunity. Although human cohort studies across the globe have established a correlation between early-life microbiota composition and atopy, mechanistic links and specific host-microorganism interactions are still being uncovered. Here, we detail the progression of immune system and microbiota maturation in early life, highlight the mechanistic links between microbes and the immune system, and summarize the role of early-life host-microorganism interactions in allergic disease development.

Type 2 and Type 17 Invariant Natural Killer T Cells Contribute to Local Eosinophilic and Neutrophilic Inflammation and Their Function Is Regulated by Mucosal Microenvironment in Nasal Polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by heterogeneous inflammatory endotypes of unknown etiology. Invariant natural killer T (iNKT) cells are multifunctional innate T cells that exhibit Th1-, Th2-, and Th17-like characteristics. We investigated functional relationships between iNKT cells and inflammatory subtypes of CRSwNP. Eighty patients with CRSwNP and thirty-two control subjects were recruited in this study. Flow cytometry was used to analyze the frequencies and functions of iNKT cells and their subsets in peripheral blood mononuclear cells (PBMCs) and tissues. Polyp tissue homogenates were used to study the multifunctionality of iNKT cells. iNKT cells were significantly increased in polyps (0.41%) than in control mucosa (0.12%). iNKT cells were determined in the paucigranunlocytic (n=20), eosinophilic (n=22), neutrophilic (n=23), and mixed granulocytic (n=13) phenotypes of CRSwNP. The percentages of iNKT cells and HLA-DR⁺PD-1⁺ subsets were lower in eosinophilic or mixed granulocytic polyps than those of other phenotypes. iNKT cells and subsets were enriched in polyp tissues than in matched PBMCs. The evaluation of surface markers, transcription factors, and signature cytokines indicated that the frequencies of iNKT2 and iNKT17 subsets were significantly increased in eosinophilic and neutrophilic polyps, respectively, than in the paucigranulocytic group. Moreover, the production of type 2 (partially dependent on IL-7) and type 17 (partially dependent on IL-23) iNKT cells could be stimulated by eosinophilic and neutrophilic homogenates, respectively. Our study revealed that type 2 and type 17 iNKT cells were involved in eosinophilic and neutrophilic inflammation, respectively, in CRSwNP, while different inflammatory microenvironments could modulate the functions of iNKT cells, suggesting a role of iNKT cells in feedback mechanisms and local inflammation.

The role of ICOS in allergic disease: Positive or Negative?

With the rapid increase in the incidence of allergic diseases, the mechanisms underlying the development of these diseases have received a great deal of attention, and this is particularly true in regard to the role of ICOS in allergic diseases. Current studies have revealed that ICOS affects the functional activity of multiple immune cells that modulate the adaptive immune system. Additionally, ICOS also plays a crucial role in mediating cellular immunity and coordinating the response of the entire immune system, and thus, it plays a role in allergic reactions. However, the ICOS/ICOS-ligand (ICOS-L) axis functions in a dual role during the development of multiple allergic diseases. In this review, we explore the role of ICOS/ICOSL in the context of different immune cells that function in allergic diseases, and we summarize recent advances in their contribution to these diseases.

Methods for Studying Mouse and Human Invariant Natural Killer T Cells

Invariant natural killer T (iNKT) cells are a unique subset of T lymphocytes that recognize lipid antigens presented by nonpolymorphic major histocompatibility complex (MHC) I-like molecule CD1d. iNKT cells play essential roles in regulating immune responses against cancer, viral infection, autoimmune disease, and allergy. However, the study and application of iNKT cells have been hampered by their very small numbers (0.01-1% in mouse and human blood). Here, we describe protocols to (1) generate mouse iNKT cells from mouse mononuclear cells or from mouse hematopoietic stem cells engineered with iNKT T cell receptor (TCR) gene (denoted as mMNC-iNKT cells or mHSC-iNKT cells, respectively), (2) generate human iNKT cells from human peripheral blood mononuclear cells or from human HSC cells engineered with iNKT TCR gene (denoted as hPBMC-iNKT cells or hHSC-iNKT cells, respectively), and (3) characterize mouse and human iNKT cells in vitro and in vivo.

Data Analysis-Driven Precise Asthmatic Treatment by Targeting Mast Cells

BACKGROUND

Although the importance of mast cells in asthma has been studied, mast cellsinduced global changes in lungs are largely unknown. Data-driven identification contributes to discovering significant biomarkers or therapeutic targets, which are the basis of effective clinical medications.

OBJECTIVE

This study aims to explore the effects of mast cells on gene expression in asthmatic lungs, and to assess the curative effects of inhaled budesonide (BUD).

METHODS

Pulmonary gene expression in KitWsh mice with or without mast cell engraftment was analyzed with R software. Functional enrichment of Gene Ontology and KEGG was carried out through the DAVID online tool. Hub genes were identified with String and Cytoscape software.

RESULTS

The array analyses showed that the mast cell engraftment enhanced inflammation/immune response, cytokine/chemokine signal, and monocyte/neutrophil/lymphocyte chemotaxis. Interleukin (IL)-6 was identified to be a significant hub gene with the highest interaction degree. Based on this, the effects of BUD were investigated on the aspects of anti-inflammation. BUD's treatment was found to reduce serum IL-6 content and pulmonary inflammation in ovalbumin-induced asthma rats. The treatment also downregulated beta-tryptase expression both in lung tissues and serum. Morphologically, the accumulation and degranulation of mast cells were significantly suppressed. Notably, the effects of BUD on inflammation and degranulation were comparable with Tranilast (a classic mast cell inhibitor), while a remarkable synergy was not observed.

CONCLUSION

This study presented a unique pulmonary gene profile induced by mast cell engraftment, which could be reversed through blockage of mast cells or inhaled BUD.

Role of CD1d- and MR1-Restricted T Cells in Asthma

Innate T lymphocytes are a group of relatively recently identified T cells that are not involved in either innate or adaptive immunity. Unlike conventional T cells, most innate T lymphocytes express invariant T cell receptor to recognize exogenous non-peptide antigens presented by a family of non-polymorphic MHC class I-related molecules, such as CD1d and MHC-related molecule-1 (MR1). Invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells quickly respond to the antigens bound to CD1d and MR1 molecules, respectively, and immediately exert effector functions by secreting various cytokines and granules. This review describes the detrimental and beneficial roles of iNKT cells in animal models of asthma and in human asthmatic patients and also addresses the mechanisms through which iNKT cells are activated by environmental or extracellular factors. We also discuss the potential for therapeutic interventions of asthma by specific antibodies against NKT cells. Furthermore, we summarize the recent reports on the role of MAIT cells in allergic diseases.

NKT cells contribute to basal IL-4 production but are not required to induce experimental asthma

CD1d-deficiency results in a selective deletion of NKT cells in mice that is reported to prevent murine allergic airway disease (AAD). Because we find 2–3 fold lower basal IL-4 production in CD1d^- mice than in wild-type (WT) mice, we hypothesized that the contribution made by NKT cells to AAD would depend on the strength of the stimulus used to induce the disease. Consequently, we compared CD1d-deficient mice to WT mice in the development of AAD, using several models of disease induction that differed in the type and dose of allergen, the site of sensitization and the duration of immunization. Surprisingly we found equivalent allergic inflammation and airway disease in WT and CD1d^- mice in all models investigated. Consistent with this, NKT cells constituted only ~2% of CD4⁺ T cells in the lungs of mice with AAD, and IL-4-transcribing NKT cells did not expand with disease induction. Concerned that the congenital absence of NKT cells might have caused a compensatory shift within the immune response, we administered an anti-CD1d monoclonal Ab (mAb) to block NKT function before airway treatments, before or after systemic sensitization to antigen. Such Ab treatment did not affect disease severity. We suggest that the differences reported in the literature regarding the significance of NKT cells in the induction of allergic airway disease may have less to do with the methods used to study the disease and more to do with the animals themselves and/or the facilities used to house them.

Animal models of asthma: utility and limitations

Clinical studies in asthma are not able to clear up all aspects of disease pathophysiology. Animal models have been developed to better understand these mechanisms and to evaluate both safety and efficacy of therapies before starting clinical trials. Several species of animals have been used in experimental models of asthma, such as Drosophila, rats, guinea pigs, cats, dogs, pigs, primates and equines. However, the most common species studied in the last two decades is mice, particularly BALB/c. Animal models of asthma try to mimic the pathophysiology of human disease. They classically include two phases: sensitization and challenge. Sensitization is traditionally performed by intraperitoneal and subcutaneous routes, but intranasal instillation of allergens has been increasingly used because human asthma is induced by inhalation of allergens. Challenges with allergens are performed through aerosol, intranasal or intratracheal instillation. However, few studies have compared different routes of sensitization and challenge. The causative allergen is another important issue in developing a good animal model. Despite being more traditional and leading to intense inflammation, ovalbumin has been replaced by aeroallergens, such as house dust mites, to use the allergens that cause human disease. Finally, researchers should define outcomes to be evaluated, such as serum-specific antibodies, airway hyperresponsiveness, inflammation and remodeling. The present review analyzes the animal models of asthma, assessing differences between species, allergens and routes of allergen administration.