The NKT cell ligand αgalactosylceramide suppresses allergic airway inflammation by induction of a Th1 response

Effects of Dendritic Cell Subset Manipulation on Airway Allergy in a Mouse Model

BACKGROUND

Two major distinct subsets of dendritic cells (DCs) are arranged to regulate immune responses: DEC-205+ DCs drive Th1 polarization and 33D1+ DCs establish Th2 dominancy. Th1 polarization can be achieved either by depletion of 33D1+ DCs with a 33D1-specific monoclonal antibody (mAb) or by activation of DEC-205+ DCs via intraperitoneal injection of α-galactosylceramide (α-GalCer). We studied the effect of 33D1+ DC depletion or DEC-205+ DC activation in vivo using an established mouse model of allergic rhinitis (AR).

METHODS

Mice were injected intraperitoneally with OVA plus alum and challenged 4 times with daily intranasal administration of OVA. Immediately after the last challenge, allergic symptoms such as sneezing and nasal rubbing as well as the number of cells in the bronchoalveolar lavage fluid (BALF) and nasal lavage fluid (NALF) were counted. The levels of serum OVA-specific IgG1, IgG2a, and IgE were also determined by ELISA.

RESULTS

The allergic symptom scores were significantly decreased in 33D1+ DC-depleted or DEC-205+ DC-activated AR mice. The levels of OVA-specific IgG1, IgG2a, and IgE, and the number of NALF cells, but not BALF cells, were reduced in 33D1+ DC-depleted but not in DEC-205+ DC-activated AR mice. Moreover, the activated DEC-205+ DCs suppressed histamine release from IgE-sensitized mast cells, probably through IL-12 secretion.

CONCLUSIONS

The manipulation of innate DC subsets may provide a new therapeutic strategy for controlling various allergic diseases by reducing histamine release from IgE-sensitized mast cells by driving the immune response towards Th1 dominancy via activation of DEC-205+ DCs in vivo.

Administration of α-Galactosylceramide Improves Adenine-Induced Renal Injury

Natural killer T (NKT) cells are a subset of lymphocytes that reacts to glycolipids presented by CD1d. Invariant NKT cells (iNKT) correspond to >90% of the total population of NKTs and reacts to α-galactosylceramide (αGalCer). αGalCer promotes a complex mixture of Th1 and Th2 cytokines, as interferon (IFN)-γ and interleukin (IL)-4. NKT cells and IFN-γ are known to participate in some models of renal diseases, but further studies are still necessary to elucidate their mechanisms. The aim of our study was to analyze the participation of iNKT cells in an experimental model of tubule-interstitial nephritis. We used 8-wk-old C57BL/6j, Jα18KO and IFN-γKO mice. They were fed a 0.25% adenine diet for 10 d. Both adenine-fed wild-type (WT) and Jα18KO mice exhibited renal dysfunction, but adenine-fed Jα18KO mice presented higher expression of kidney injury molecule-1 (KIM-1), tumor necrosis factor (TNF)-α and type I collagen. To analyze the role of activated iNKT cells in our model, we administered αGalCer in WT mice during adenine ingestion. After αGalCer injection, we observed a significant reduction in serum creatinine, proinflammatory cytokines and renal fibrosis. However, this improvement in renal function was not observed in IFN-γKO mice after αGalCer treatment and adenine feeding, illustrating that this cytokine plays a role in our model. Our findings may suggest that IFN-γ production is one of the factors contributing to improved renal function after αGalCer administration.

Impact of endobronchial allergen provocation on macrophage phenotype in asthmatics

Background

The role of M2 polarized macrophages (MΦ) during the allergic airway inflammation has been discussed in various animal models. However, their presence and relevance during the chronic and acute phase of allergic airway inflammation in humans has not been fully elucidated so far. In the present study we phenotypically characterized macrophages with regard to M2 polarization in mice, a human in vitro and a human ex vivo model with primary lung cells after endobronchial provocation.

Results

Macrophages remained polarized beyond clearance of the acute allergic airway inflammation in mice. Alveolar macrophages of asthmatics revealed increased mRNA expression of CCL13, CCL17 and CLEC10A in response to allergen challenge as well as increased surface expression of CD86. Further, mRNA expression of CCL13, CCL17, and CLEC10A was increased in asthmatics at baseline compared to healthy subjects. The mRNA expression of CCL17 and CLEC10A correlated significantly with the degree of eosinophilia (each P < .01). Furthermore, macrophages from asthmatics released significant amounts of CCL17 protein in vitro which was also found increased in BAL fluid after allergen provocation.

Conclusions

This study supports previous findings of M2 macrophage polarization in asthmatic subjects during the acute course of the allergic inflammation and provides evidence for their contribution to the Th2 inflammation.

The role of natural killer (NK) and NK T cells in the loss of tolerance in murine primary biliary cirrhosis

One of the major obstacles in dissecting the mechanism of pathology in human primary biliary cirrhosis (PBC) has been the absence of animal models. Our laboratory has focused on a model in which mice, following immunization with a xenobiotic chemical mimic of the immunodominant autoepitope of the E2 component of pyruvate dehydrogenase complex (PDC-E2), develop autoimmune cholangitis. In particular, following immunization with 2-octynoic acid (a synthetic chemical mimic of lipoic acid-lysine located within the inner domain of PDC-E2) coupled to bovine serum albumin (BSA), several strains of mice develop typical anti-mitochondrial autoantibodies and portal inflammation. The role of innate immune effector cells, such as natural killer (NK) cells and that NK T cells, was studied in this model based on the hypothesis that early events during immunization play an important role in the breakdown of tolerance. We report herein that, following in-vivo depletion of NK and NK T cells, there is a marked suppression of anti-mitochondrial autoantibodies and cytokine production from autoreactive T cells. However, there was no change in the clinical pathology of portal inflammation compared to controls. These data support the hypothesis that there are probably multiple steps in the natural history of PBC, including a role of NK and NK T cells in initiating the breakdown of tolerance. However, the data suggest that adaptive autoimmune effector mechanisms are required for the progression of clinical disease.

The role of natural killer (NK) and NK T cells in the loss of tolerance in murine primary biliary cirrhosis

One of the major obstacles in dissecting the mechanism of pathology in human primary biliary cirrhosis (PBC) has been the absence of animal models. Our laboratory has focused on a model in which mice, following immunization with a xenobiotic chemical mimic of the immunodominant autoepitope of the E2 component of pyruvate dehydrogenase complex (PDC-E2), develop autoimmune cholangitis. In particular, following immunization with 2-octynoic acid (a synthetic chemical mimic of lipoic acid-lysine located within the inner domain of PDC-E2) coupled to bovine serum albumin (BSA), several strains of mice develop typical anti-mitochondrial autoantibodies and portal inflammation. The role of innate immune effector cells, such as natural killer (NK) cells and that NK T cells, was studied in this model based on the hypothesis that early events during immunization play an important role in the breakdown of tolerance. We report herein that, following in-vivo depletion of NK and NK T cells, there is a marked suppression of anti-mitochondrial autoantibodies and cytokine production from autoreactive T cells. However, there was no change in the clinical pathology of portal inflammation compared to controls. These data support the hypothesis that there are probably multiple steps in the natural history of PBC, including a role of NK and NK T cells in initiating the breakdown of tolerance. However, the data suggest that adaptive autoimmune effector mechanisms are required for the progression of clinical disease.

MicroRNAs are key regulators controlling iNKT and regulatory T-cell development and function

MicroRNAs (miRNAs) are an abundant class of evolutionarily conserved, small, non-coding RNAs that post-transcriptionally regulate expression of their target genes. Emerging evidence indicates that miRNAs are important regulators that control the development, differentiation and function of different immune cells. Both CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells and invariant natural killer T (iNKT) cells are critical for immune homeostasis and play a pivotal role in the maintenance of self-tolerance and immunity. Here, we review the important roles of miRNAs in the development and function of iNKT and Treg cells.