Phenotypic changes to the endogenous antigen-specific CD8+ T cell response correlates with the development and resolution of allergic airway disease

IL-15-deficient mice develop enhanced allergic responses to airway allergen exposure

BACKGROUND

Interleukin-15 is a pleiotropic cytokine that is critical for the development and survival of multiple haematopoietic lineages. Mice lacking IL-15 have selective defects in populations of several pro-allergic immune cells including natural killer (NK) cells, NKT cells, and memory CD8+ T cells. We therefore hypothesized that IL-15-/- mice will have reduced inflammatory responses during the development of allergic airway disease (AAD).

OBJECTIVE

To determine whether IL-15-/- mice have attenuated allergic responses in a mouse model of AAD.

METHODS

C57BL/6 wild-type (WT) and IL-15-/- mice were sensitized and challenged with ovalbumin (OVA), and the development of AAD was ascertained by examining changes in airway inflammatory responses, Th2 responses, and lung histopathology.

RESULTS

Here, we report that IL-15-/- mice developed enhanced allergic responses in an OVA-induced model of AAD. In the absence of IL-15, OVA-challenged mice exhibited enhanced bronchial eosinophilic inflammation, elevated IL-13 production, and severe lung histopathology in comparison with WT mice. In addition, increased numbers of CD4+ T and B cells in the spleens and bronchoalveolar lavage (BAL) were also observed. Examination of OVA-challenged IL-15Rα-/- animals revealed a similar phenotype resulting in enhanced airway eosinophilia compared to WT mice. Adoptive transfer of splenic CD8+ T cells from OVA-sensitized WT mice suppressed the enhancement of eosinophilia in IL-15-/- animals to levels observed in WT mice, but had no further effects.

CONCLUSION AND CLINICAL RELEVANCE

These data demonstrate that mice with an endogenous IL-15 deficiency are susceptible to the development of severe, enhanced Th2-mediated AAD, which can be regulated by CD8+ T cells. Furthermore, the development of disease as well as allergen-specific Th2 responses occurs despite deficiencies in several IL-15-dependent cell types including NK, NKT, and γδ T cells, suggesting that these cells or their subsets are dispensable for the induction of AAD in IL-15-deficient mice.

Long-Term Exposure to House Dust Mite Leads to the Suppression of Allergic Airway Disease Despite Persistent Lung Inflammation

BACKGROUND

Allergic asthma is a major cause of worldwide morbidity and results from inadequate immune regulation in response to innocuous, environmental antigens. The need exists to understand the mechanisms that promote nonreactivity to human-relevant allergens such as house dust mite (HDM) in order to develop curative therapies for asthma. The aim of our study was to compare the effects of short-, intermediate- and long-term HDM administration in a murine asthma model and determine the ability of long-term HDM exposure to suppress allergic inflammation.

METHODS

C57BL/6 mice were intranasally instilled with HDM for short-term (2 weeks), intermediate-term (5 weeks) and long-term (11 weeks) periods to induce allergic airway disease (AAD). The severity of AAD was compared across all stages of the model via both immunological and pulmonary parameters.

RESULTS

Short- and intermediate-term HDM exposure stimulated the development of AAD that included eosinophilia in the bronchoalveolar lavage fluid (BALF), pronounced airway hyperreactivity (AHR) and evidence of lung inflammation. Long-term HDM exposure promoted the suppression of AAD, with a loss of BALF eosinophilia and AHR despite persistent mononuclear inflammation in the lungs. Suppression of AAD with long-term HDM exposure was associated with an increase in both Foxp3+ regulatory T cells and IL-10-positive alveolar macrophages at the site of inflammation.

CONCLUSIONS

This model recapitulates the key features of human asthma and may facilitate investigation into the mechanisms that promote immunological tolerance against clinically relevant aeroallergens.

Regulatory B cells in allergic airways disease and asthma

B cells have long been known to participate in both innate and adaptive immune responses by contributing to antigen presentation and by producing antigen-specific antibodies. Recent evidence shows that certain B-cell subsets can also inhibit T-cell immune responses. Like regulatory T cells (Treg), these regulatory B cells (Breg) appear to comprise several subpopulations. How Breg cells are generated and how they control immune responses in vivo are just beginning to be elucidated. Here, we provide detailed instructions for the identification, isolation, and functional characterization of Breg cells in a murine model of allergic airway disease.

A novel pentapeptide originated from calf thymus named TIPP shows an inhibitory effect on lung allergic inflammation

Thymic immunosuppressive pentapeptide (TIPP) is a novel pentapeptide originally obtained from calf thymic immunosuppressive extract. In this study we aimed to investigate the anti-inflammatory effect and mechanisms of TIPP in vivo with an ovalbumin-induced mouse allergic asthma model. We investigated the effects of TIPP on the infiltration of inflammation cells, immune cell subtypes, Th2 cytokines in BALF and IgE in serum, mRNA levels of IL-4, IL-10, TNF-α and eotaxin-1, expression of MCP-1, VCAM-1 and COX-2, and activation of MAP kinases and NF-κB. Our results showed that TIPP significantly inhibited the increase in Th2 cytokines and OVA-specific IgE production, mRNA levels of IL-4, TNF-α and eotaxin-1 and the expression of MCP-1, VCAM-1 and COX-2 in lung tissues, as well effectively resisting the balance changes of cells in BALF. In addition, it was found that the administration of TIPP attenuated the activation of MAP kinases and NF-κB in the lung tissues of the allergic mice. Our data suggest that TIPP effectively suppresses the allergic and inflammatory responses in allergic mice via blocking MAP kinases/NF-κB signalling pathway. The investigation indicated that TIPP may become an anti-allergic and anti-inflammatory drug.