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.

The presence of CD8+ invariant NKT cells in mice

Invariant natural killer T (iNKT) cells develop in the thymus upon recognition of CD1d expressed on developing thymocytes. Although CD4 and CD8 coreceptors are not directly involved in the interaction between CD1d and the T cell receptors (TCRs) of iNKT cells, a conspicuous lack of CD8+ iNKT cells in mice raised the question of whether CD8+ iNKT cells are excluded due to negative selection during their thymic development, or if there is no lineage commitment for the development of murine CD8+ iNKT cells. To address this question, we analyzed iNKT cell-specific TCR Valpha14+ transgenic mice, where the Valpha14 transgene forces the generation of iNKT cells. This allows detailed study of the iNKT cell repertoire. We were able to identify CD8+ iNKT cells which respond to the NKT cell-specific glycolipid ligand alpha-galactosylceramide. Unlike conventional iNKT cells, CD8+ iNKT cells produce predominantly IFN-gamma but not IL-4 upon antigen stimulation. We also confirmed the presence of CD8+ iNKT cells in wild type mice. Our results suggest that CD8+ NKT cells do exist in mice, although their population size is quite small. Their Th1-skewed phenotype might explain why the population size of this subtype needs to be controlled tightly.

IL-12 p40-Expressing Immune Cells Revealed by Cytokine Reporter Mouse System / 체질인류학회지

Interleukin-12 (IL-12), consisting of p35 and p40, plays important roles in linking innate and adaptive immunity. While p35 is constitutively expressed, IL-12 p40 gene expression is induced upon activation by Toll-like receptor ligands. Recently, with gene targeting technology, the cytokine IL-12 p40 reporter mouse has been developed to express the p40 gene linked via a viral IRES element with yellow fluorescence protein (YFP) fluorescent reporter. We investigated whether this novel system would be useful to reveal IL-12 p40-producing immune cells. We first investigated whether macrophages and dendritic cells from these mice faithfully reported p40 induction. Next, we tested if microglial cells, macrophages in the brain, could induce IL-12 p40. Finally we tested whether B cells could produce IL-12 p40 because there were very few reports for IL-12 production by B cells. Our results confirmed that macrophages and dendritic cells are main producer of IL-12 p40. Then, we found that microglial cells could produce IL-12 p40 upon stimulation with various TLR ligands. Finally we found that a subset of B cells could produce IL-12 p40 in TLR9-dependent manner. Taken all together, our system will be a valuable tool to identify the type of immune cells that produce IL-12 p40.

Anti-tumor immunostimulatory effect of heat-killed tumor cells

As a part of our ongoing search for a safe and efficient anti-tumor vaccine, we attempted to determine whether the molecular nature of certain tumor antigens would influence immune responses against tumor cells. As compared with freeze-thawed or formaldehyde-fixed tumor antigens, heat-denatured tumor antigens elicited profound anti-tumor immune responses and greatly inhibited the growth of live tumor cells. The heat-denatured tumor antigens induced a substantial increase in the anti-tumor CTL response in the absence of any adjuvant material. This response appears to be initiated by strong activation of the antigen-presenting cells, which may recognize heat-denatured protein antigens. Upon recognition of the heat-denatured tumor antigens, macrophages and dendritic cells were found to acutely upregulate the expression of co-stimulatory molecules such as B7.2, as well as the secretion of inflammatory cytokines such as IL-12 and TNF-alpha. The results of this study indicate that heat-denatured tumor extracts might elicit protective anti-tumor adaptive immune responses and also raise the possibility that a safe and efficient adjuvant-free tumor vaccine might be developed in conjunction with a dendritic cell-based tumor vaccine.

The Immunostimulatory Effect of B16 Freezing/thawing Anti-tumor Vaccine / 체질인류학회지

Since cancer has become the second most common cause of death, next to heart disease and approximately 20% of human population dies from cancer, it is much desired to develop therapeutic anti-tumor vaccine with safety and efficacy. Here we investigated the immunostimulatory effects of B16 freezing/thawing (F/T) anti-tumor vaccine (hereafter F/T vaccine), one of whole cell anti-tumor vaccines. To this end, we took advantage of the IL12 p40 reporter system which is designed for monitoring the induction of IL12 expression via the detection of co-expressed yellow fluorescent protein. First, we examined whether F/T vaccine can induce IL12 expression using bone marrow-derived dendritic cells (BMDCs) from IL12 p40 reporter mice. Second, we examined whether F/T vaccine can change the expression level of MHC molecules and co-stimulatory molecules during the activation of dendritic cells. Third, to dissect what component of F/T vaccines accounts for the immunostimulatory activities, we examined the effect of F/T vaccine on BMDC activation after treating it with DNase or proteinase. Lastly, we used MyD88 knockout mice to investigate whether F/T vaccine activates BMDCs in a TLRdependent manner. We found that treatment of BMDCs with F/T vaccine induced IL12 expression as well as the increase of MHC II expression and co-stimulatory molecules such as CD86. Interestingly, we also found that F/T vaccine increased CD1d expression on BMDCs, which may influence the activation of natural killer T cells known to be involved in anti-tumor immune responses. In addition, we found that treatment of F/T vaccine with proteinase but not DNase abolished its immunostimulatory effect, indicating that proteins in F/T vaccine mainly have its adjuvant activity. Furthermore, the activation of BMDCs with F/T vaccine was dependent on MyD88 adaptor molecule. Taken together, our findings in this study demonstrated that the F/T vaccine might be one of the valuable reagents to provide a new insight for underlying mechanism of whole-cell anti-tumor vaccines and an important clue for the development of better therapeutic anti-cancer vaccines.

Screening of Interleukin-12/interleukin-23 p40 Inducers in Rheumatoid Synovial Fluids by Fluorescence Reporter Mouse System / 체질인류학회지

Although rheumatoid arthritis has been known to be a common autoimmune disease characterized by chronic inflammation mainly evident in diarthrodial joints, its pathogenesis remains to be clarified. In the present study, to investigate the pathogenic signaling system taken place in the rheumatoid joints, we assessed whether synovial fluid obtained from patients with rheumatoid arthritis contains inducers for proinflammatory cytokines such as interleukin (IL)-12 and IL-23. Peritoneal macrophages isolated from IL-12/IL-23 p40-YFP reporter mice were stimulated with synovial fluid, followed by flow cytometry to screen CD11b+ and YFP-expressing cells, reflective of IL-12/IL-23 p40-producing macrophages. The expression levels of Toll-like receptor (TLR)-2 and -4, which have a potential to mediate IL-12/IL- 23 p40 induction, were determined in synovial cells obtained from a patient with rheumatoid arthritis by RT-PCR analyses. One out of 10 synovial fluid from rheumatoid arthritis patients induced IL-12/IL-23 p40 expression, while all of 10 synovial fluid from osteoarthritis patients did not. Synoviocytes constitutively expressed Toll-like receptor (TLR)-2 and -4 which are candidate receptors for IL-12/IL-23 inducers. Upon LPS stimulation, the levels of TLR-2 and -4 were downregulated and upregulated, respectively. Taken together, these results suggest that some patients with rheumatoid arthritis elicit synovitis through TLR-2- and -4-mediated induction of proinflammatory cytokines IL-12 and IL-23.

Alteration of Innate Immune T and B Cells in the NC/Nga Mouse

BACKGROUND: Millions of people in the world are suffering from atopic dermatitis (AD), which is a chronic inflammatory skin disease triggered by Th2 immune responses. The NC/Nga mouse is the most extensively studied animal model of AD. Like human AD, NC/Nga mice demonstrate increased levels of IgE, a hallmark of Th2 immune responses. Adaptive immunity cannot be generated without help of innate immunity. Especially natural killer T (NKT) cells and marginal zone B (MZB) cells have been known to play important roles in linking innate immunity to adaptive immunity. METHODS: Through flow cytometric analysis and ELISA assay, we investigated whether these lymphocytes might be altered in number in NC/Nga mice. RESULTS: Our data demonstrated that the number of NKT cells was reduced in NC/Nga mice and IFNgamma production by NKT cells upon alpha-GalCer stimulation decreased to the levels of CD1d KO mice lacking in NKT cells. However, reduction of NKT cells in NC/Nga mice was not due to CD1d expression, which was normal in the thymus. Interestingly, there was a significant increase of CD1d(high)B220+ cells in the spleen of NC/Nga mice. Further, we confirmed that CD1d(high)B220+ cells are B cells, not dendritic cells. These CD1d(high)B220+ B cells show IgM(high)CD21(high)CD23low, a characteristic phenotype of MZB cells. CONCLUSION: We provide the evidence that there are decreased activities of NKT cells and increased number of MZB cells in the NC/Nga mice. Our findings may thus explain why NC/Nga mice are susceptible to AD.