Basophil-Derived IL-4 and IL-13 Protect Intestinal Barrier Integrity and Control Bacterial Translocation during Malaria

Our previous work demonstrated that basophils regulate a suite of malaria phenotypes, including intestinal mastocytosis and permeability, the immune response to infection, gametocytemia, and parasite transmission to the malaria mosquito Anopheles stephensi. Given that activated basophils are primary sources of the regulatory cytokines IL-4 and IL-13, we sought to examine the contributions of these mediators to basophil-dependent phenotypes in malaria. We generated mice with basophils depleted for IL-4 and IL-13 (baso IL-4/IL-13 (-)) and genotype controls (baso IL-4/IL-13 (+)) by crossing mcpt8-Cre and Il4/Il13fl/fl mice and infected them with Plasmodium yoelii yoelii 17XNL. Conditional deletion was associated with ileal mastocytosis and mast cell (MC) activation, increased intestinal permeability, and increased bacterial 16S levels in blood, but it had no effect on neutrophil activation, parasitemia, or transmission to A. stephensi. Increased intestinal permeability in baso IL-4/IL-13 (-) mice was correlated with elevated plasma eotaxin (CCL11), a potent eosinophil chemoattractant, and increased ileal MCs, proinflammatory IL-17A, and the chemokines MIP-1α (CCL3) and MIP-1β (CCL4). Blood bacterial 16S copies were positively but weakly correlated with plasma proinflammatory cytokines IFN-γ and IL-12p40, suggesting that baso IL-4/IL-13 (-) mice failed to control bacterial translocation into the blood during malaria infection. These observations suggest that basophil-derived IL-4 and IL-13 do not contribute to basophil-dependent regulation of parasite transmission, but these cytokines do orchestrate protection of intestinal barrier integrity after P. yoelii infection. Specifically, basophil-dependent IL-4/IL-13 control MC activation and prevent infection-induced intestinal barrier damage and bacteremia, perhaps via regulation of eosinophils, macrophages, and Th17-mediated inflammation.

Changes in type 2 innate lymphoid cells and serum cytokines in sublingual immunotherapy in pediatric patients with allergic rhinitis

BACKGROUND

Type 2 innate lymphoid cells (ILC2) are upregulated in childhood allergic rhinitis (AR) and are associated with AR severity. This study aimed to investigate changes in the ILC2 milieu in pediatric patients with AR after sublingual immunotherapy (SLIT).

METHODS

Forty- pediatric patients with AR received house dust mite (HDM) allergen extract for SLIT group and thirty pediatric patients received placebo in the study, respectively. The levels of ILC2, ILC2-related cytokines (IL-5/IL-13) and their transcription factors (GATA binding protein 3, retinoic acid-related orphan receptor α) in the circulation were assessed after 1- and 2-year SLIT. Moreover, peripheral blood mononuclear cells (PBMCs) in patients were prepared and stimulated by recombinant thymic stromal lymphopoietin, IL-25, and IL-33 after 2-year SLIT. Subsequently, the levels of ILC2, IL-5, and IL-13 were tested.

RESULTS

The frequency of ILC2 and the levels of their transcription factors in the circulation were significantly decreased after SLIT in the SLIT group. The levels of ILC2-related cytokines in the SLIT group showed the same trend. The frequency of ILC2 was positively correlated with transcription factors and cytokines after SLIT. SLIT was observed to reduce the ability of HDM sensitization to generate the ILC2 milieu in PBMCs.

CONCLUSIONS

Changes in the ILC2 milieu may be correlated with the curative effect and immune regulation function of SLIT. Our results suggested that the regulatory effect on ILC2 is part of the therapeutic mechanism of SLIT.

Regulation of Skin Barrier Function via Competition between AHR Axis versus IL-13/IL-4‒JAK‒STAT6/STAT3 Axis: Pathogenic and Therapeutic Implications in Atopic Dermatitis

Atopic dermatitis (AD) is characterized by skin inflammation, barrier dysfunction, and chronic pruritus. As the anti-interleukin-4 (IL-4) receptor α antibody dupilumab improves all three cardinal features of AD, the type 2 cytokines IL-4 and especially IL-13 have been indicated to have pathogenic significance in AD. Accumulating evidence has shown that the skin barrier function is regulated via competition between the aryl hydrocarbon receptor (AHR) axis (up-regulation of barrier) and the IL-13/IL-4‒JAK‒STAT6/STAT3 axis (down-regulation of barrier). This latter axis also induces oxidative stress, which exacerbates inflammation. Conventional and recently developed agents for treating AD such as steroid, calcineurin inhibitors, cyclosporine, dupilumab, and JAK inhibitors inhibit the IL-13/IL-4‒JAK‒STAT6/STAT3 axis, while older remedies such as coal tar and glyteer are antioxidative AHR agonists. In this article, I summarize the pathogenic and therapeutic implications of the IL-13/IL-4‒JAK‒STAT6/STAT3 axis and the AHR axis in AD.

The Role of the TL1A/DR3 Axis in the Activation of Group 2 Innate Lymphoid Cells in Subjects with Eosinophilic Asthma

Rationale: Group 2 innate lymphoid cells (ILC2s) are critical for type 2 inflammation. In murine models of asthma, some ILC2s remain activated in the absence of epithelial cell-derived cytokine signaling, implicating alternate stimulatory pathways. DR3 (death receptor 3), a member of the tumor necrosis factor receptor superfamily, is expressed on ILC2s. Genome-wide association studies report an association between DR3 ligand, TL1A (tumor necrosis factor-like protein 1A), and chronic inflammatory conditions.Objectives: We investigated the TL1A/DR3 axis in airway ILC2 biology in eosinophilic asthma.Methods: Stable subjects with mild asthma were subject to allergen inhalation challenge, and DR3 expression on sputum cells was assessed. We investigated cytokine regulation of DR3 expression on ILC2s and steroid sensitivity. Airway TL1A was assessed in sputum from subjects with mild asthma and subjects with prednisone-dependent severe eosinophilic asthma.Measurements and Main Results: There was a significant increase in sputum DR3⁺ ILC2s 24 hours after allergen challenge, and DR3 expression on ILC2s was upregulated by IL-2, IL-33, or TSLP in vitro. Stimulation with TL1A significantly increased IL-5 expression by ILC2s and was attenuated by dexamethasone, an effect that was negated in the presence of TSLP. Airway TL1A levels were increased 24 hours after allergen challenge in subjects with mild asthma but were significantly greater in those with severe eosinophilic asthma. The highest levels were detected in subjects with severe asthma with airway autoimmune responses. C1q⁺ immune complexes from the sputa of subjects with severe asthma with high autoantibody levels stimulated TL1A production by monocytes.Conclusions: The TL1A/DR3 axis is a costimulator of ILC2s in asthma, particularly in the airways of patients with a predisposition to autoimmune responses.

Characterization of immune responses and the lung transcriptome in a murine model of IL-33 challenge

IL-33 induces airway inflammation and hyper-responsiveness in respiratory diseases. Although defined as a therapeutic target, there are limited studies that have comprehensively investigated IL-33-mediated responses in the lungs in vivo. In this study, we characterized immunological and physiological responses induced by intranasal IL-33 challenge, in a mouse model. We identified specific cytokines, IL-4, IL-5, IL-6, IL-10, IP-10 and MIP1-α, that are increased in bronchoalveolar lavage and lung tissues by IL-33. Using transcriptomics (RNA-Seq) we demonstrated that 2279 transcripts were up-regulated and 1378 downregulated (≥ 2-fold, p < 0.01) in lung tissues, in response to IL-33. Bioinformatic interrogation of the RNA-Seq data was used to predict biological pathways and upstream regulators involved in IL-33-mediated responses. We showed that the mRNA and protein of STAT4, a predicted upstream regulator of IL-33-induced transcripts, was significantly enhanced in the lungs following IL-33 challenge. Overall, this study provides specific IL-33-induced molecular targets and endpoints that can be used as a resource for in vivo studies, e.g. in preclinical murine models examining novel interventions to target downstream effects of IL-33.

Salidroside suppresses group 2 innate lymphoid cell-mediated allergic airway inflammation by targeting IL-33/ST2 axis

Salidroside, an active component extracted from Rhodiola rosea, has been reported to inhibit allergic asthma. However, its mechanism has not been fully elucidated. Group 2 innate lymphoid cells (ILC2s) accumulate in the lung and cooperate with other cells to drive type 2 inflammation stimulated by inhaled allergens. The study aims to explore the suppressive effect of salidroside on ILC2s and IL-33/IL-33R (ST2) axis in allergic airway inflammation. The ovalbumin (OVA)-sensitized/challenged mice were established. Airway eosinophil recruitment, increased total IgE in the serum and type 2 cytokines IL-4, IL-5, and IL-13 in the bronchoalveolar lavage fluids and lung tissues were identified in the OVA-induced mice model, all of which were inhibited by pretreatment with different doses of salidroside. Moreover, salidroside suppressed lung total ILC2 and ST2-expressing ILC2 accumulation, lung IL-33 and ST2 expressions in mice. In vitro, OVA could induce IL-33 expression in BEAS-2B cells, which was also effectively inhibited by salidroside. This study firstly reveals salidroside as a potential therapeutic drug for allergic asthma by inhibiting ILC2-mediated airway inflammation via targeting IL-33/ST2 axis.

The role of type 2 innate lymphoid cells in eosinophilic asthma

Eosinophilic asthma has conventionally been proposed to be a T helper 2 driven disease but emerging evidence supports a central role of type 2 innate lymphoid cells (ILC2s). These are non-T, non-B cells that lack antigen specificity and produce more IL-5 and IL-13 than CD4⁺ T lymphocytes, on a cell per cell basis, in vitro. Although it is clear that ILC2s and CD4⁺ T cells work in concert with each other to drive type 2 immune responses, kinetic studies in allergic asthma suggest that ILC2s may act locally within the airways to "initiate" eosinophilic responses, whereas CD4⁺ T cells act locally and systemically to "perpetuate" eosinophilic inflammatory responses. Importantly, ILC2s are increased within the airways of severe asthmatics, with the greatest number of IL-5⁺ IL-13⁺ ILC2s being detected in sputum from severe asthmatics with uncontrolled eosinophilia despite high-dose steroid therapy. Although the precise relationship between ILC2s and steroid sensitivity in asthma remains unclear, controlling the activation of ILC2s within the airways may provide an effective therapeutic target for eosinophilic inflammation in airways diseases.

The Endothelin-A Receptor Antagonist Zibotentan Induces Damage to the Nasal Olfactory Epithelium Possibly Mediated in Part through Type 2 Innate Lymphoid Cells

Zibotentan, an endothelin-A receptor antagonist, has been used in the treatment of various cardiovascular disorders and neoplasia. Castrated athymic nude mice receiving zibotentan for a preclinical xenograft efficacy study experienced weight loss, gastrointestinal bloat, and the presence of an audible respiratory click. Human side effects have been reported in the nasal cavity, so we hypothesized that the nasal cavity is a target for toxicity in mice receiving zibotentan. Lesions in the nasal cavity predominantly targeted olfactory epithelium in treated mice and were more pronounced in castrated animals. Minimal lesions were present in vehicle control animals, which suggested possible gavage-related reflux injury. The incidence, distribution, and morphology of lesions suggested direct exposure to the nasal mucosa and a possible systemic effect targeting the olfactory epithelium, driven by a type 2 immune response, with group 2 innate lymphoid cell involvement. Severe nasal lesions may have resulted in recurrent upper airway obstruction, leading to aerophagia and associated clinical morbidity. These data show the nasal cavity is a target of zibotentan when given by gavage in athymic nude mice, and such unanticipated and off-target effects could impact interpretation of research results and animal health in preclinical studies.

Endotypes of severe allergic asthma patients who clinically benefit from anti-IgE therapy

BACKGROUND

Omalizumab, a recombinant monoclonal anti-IgE antibody, was developed for the treatment of severe allergic asthma. Not all these patients respond to omalizumab.

OBJECTIVE

This study aimed to evaluate whether the proinflammatory cytokine profiles in the severe allergic asthma patients were different between who responded and nonresponded to omalizumab therapy.

METHODS

A prospective study was conducted to examine type 2 cytokines and epithelium-derived cytokines in the bronchial tissues by immunohistochemistry, Western blot and PCR analysis among patients with severe allergic asthma before and after omalizumab therapy.

RESULTS

Fourteen of 23 patients with unstable severe allergic asthma improved their asthma control after 4 months of omalizumab treatment (Responders), while nine failed to improve (Non-Responders). Most of Responders were type 2-high endotype (12/14) with upregulated expression of IL-33, IL-25 and TSLP in their bronchial tissues, while most of Non-Responders were type 2-low endotype (8/9). Repeated bronchoscopic biopsy was done in nine responders after omalizumab treatment and showed a decline in IL-13, IL-33, IL-25 and TSLP expression in the bronchial tissues. Among 14 Responders who continued omalizuamb treatments to a total 12 months, six patients achieved a well control of asthma (ACT ≥ 23), while eight patients required additional treatment for asthma symptoms and had more rhinosinusitis comorbidities and a mixed eosinophilic and neutrophilic inflammation in their bronchial tissues.

CONCLUSION

Most of the severe allergic asthma patients who benefited from omalizumab treatment were IL-33, IL-25 and TSLP aggravated type 2-high endotype. Rhinosinusitis or with a mixed eosinophilic and neutrophilic airway inflammation should be evaluated in patients who partially responded to omalizumab treatment.

The Hunt for the Source of Primary Interleukin-4: How We Discovered That Natural Killer T Cells and Basophils Determine T Helper Type 2 Cell Differentiation In Vivo

Interleukin (IL)-4 plays a central role in determining the phenotype of naïve CD4⁺ T cells by promoting their differentiation into IL-4-producing T helper type 2 (Th2) cells, which are crucial for the induction of allergic inflammation. However, to date, the potential sources of “primary IL-4” in vivo, as distinguished from IL-4 produced by Th2 cells, remain unclear. Here, I describe the research I carried out in collaboration with Dr. William E. Paul to identify “primary IL-4”-producing cells and Th2 cell differentiation in vivo.