Toll-like receptor-dependent IL-12 production by dendritic cells is required for activation of natural killer cell-mediated Type-1 immunity induced by Chrysanthemum Coronarium L

A Designed α-GalCer Analog Promotes Considerable Th1 Cytokine Response by Activating the CD1d-iNKT Axis and CD11b-Positive Monocytes/Macrophages

Selective helper T cell 1 (Th1) priming agonists are a promising area of investigation for immunotherapeutic treatment of various diseases. α-galactosylceramide (α-GalCer, KRN7000), a well-studied Th1-polarizer, simultaneously induces helper T cell 2 (Th2)-type responses, which is a major drawback for its clinical applications. Based on surflex-docking computation, α-GalCer-diol, with added hydroxyl groups in the acyl chain, is designed and synthesized. Structural analyses reveal stronger affinity between α-GalCer-diol and cluster of differentiation 1d (CD1d), leading to enhanced antigen presentation by dendritic cells (DCs) and self-activation, as reflected by tight binding of the T-cell receptor (TCR)/KRN7000/CD1d ternary complex and elevated production of interleukin 12 (IL-12) and interferon-γ (IFN-γ). Consequently, invariant natural killer T cells (iNKTs) are activated and exhibit an improved Th1-type cytokine profile ex vivo and in vivo. Different from KRN7000, α-GalCer-diol markedly boosts the expansion of the CD11b+ subpopulation and enhances IFN-γ content in CD11b+ cells. These reinforced Th1-type responses collectively endow α-GalCer-diol more robust antitumor activity in a xenograft animal model using B16-F10 melanoma cells. Together, the data demonstrate a new mechanism through which α-GalCer-diol induces stronger Th1-type responses by stimulating CD11b+ leukocyte expansion and DC-conducted CD1d-restricted and TCR-mediated iNKT activation. Hence, this study may facilitate the development of novel Th1 priming agonists.

Enhancement of natural killer activity and IFN-γ production in an IL-12-dependent manner by a Brassica rapa L

Certain food components possess immunomodulatory effects. The aim of this study was to elucidate the mechanism of the immunostimulatory activity of Brassica rapa L. We demonstrated an enhancement of natural killer (NK) activity and interferon (IFN)-γ production in mice that were orally administered an insoluble fraction of B. rapa L. The insoluble fraction of B. rapa L. significantly induced IFN-γ production in mouse spleen cells in an interleukin (IL)-12-dependent manner, and NK1.1+ cells were the main cells responsible for producing IFN-γ. Additionally, the results suggested that the active compounds in the insoluble fraction were recognized by Toll-like receptor (TLR) 2, TLR4, and C-type lectin receptors on dendritic cells, and they activated signaling cascades such as MAPK, NF-κB, and Syk. These findings suggest that B. rapa L. is a potentially promising immuno-improving material, and it might be useful for preventing immunological disorders such as infections and cancers by activating innate immunity.

Modulation of dendritic cell immune functions by plant components

Dendritic cells (DCs) are the key linkage between innate and adoptive immune response. DCs are classified as specialized antigen-presenting cells that initiate T-cell immune responses during infection and hypersensitivity, and maintain immune tolerance to self-antigens. Initiating T-cell immune responses may be beneficial in infectious diseases or cancer management, while, immunosuppressant or tolerogenic responses could be useful in controlling autoimmunity, allergy or inflammatory diseases. Several types of plant-derived components show promising properties in influencing DC functions. Various types of these components have been proven useful in clinical application and immune-based therapy. Therefore, focusing on the benefits of plant-based medicine regulating DC functions may be useful, low-cost, and accessible strategies for human health. This review illustrates recent studies, investigating the role of plant components in manipulating DC phenotype and function towards immunostimulating or immunosuppressing effects either in vitro or in vivo.

TLR7/8 agonists promote NK-DC cross-talk to enhance NK cell anti-tumor effects in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common cancer worldwide and the third leading cause of cancer death. Immunotherapy is considered a promising treatment with the aim to boost or arouse HCC-specific immune responses. TLR7 and TLR8 agonists are effective immunomodulators and have been applied topically for the treatment of certain skin tumors and viral infections. Here, we explored the role of TLR7 and TLR8 agonists on the activation of dendritic cells (DCs) and natural killer (NK) cells. We demonstrated that these agonists could directly activate NK cells, promoting the maturation of immature DCs. Meanwhile, DCs also assisted in the function of NK cells, resulting in enhanced anti-tumor immune responses to HCC. Importantly, the combination therapy with NK cells stimulated with DCs and TLR7/8 agonist Gardiquimod (GDQ) significantly suppresses the growth of human HepG2 liver carcinoma xenografts. This study provides a new immunotherapeutic approach for human HCC based on DC-NK cross-talk and also suggests that TLR7 and/or TLR8 agonists, particularly GDQ, may serve as potent innate and adaptive immune response immunomodulators in tumor therapy.

The immunoregulatory effects of Chinese herbal medicine on the maturation and function of dendritic cells

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese herbal medicine (CHM) has a long-history for treatment of various human diseases including tumors, infection, autoimmune diseases in Asian countries, especially in China, Japan, Korea and India. CHM was traditionally used as water extracts and many Chinese herbs were considered to be good for health, which can regulate immune system to protect host from diseases. With the progress of technology, the components of CHM were identified and purified, which included polysaccharides, saponins, phenolic compounds, flavonoids and so on. Recently, accumulating evidence indicates that CHM and its components can regulate immune system through targeting dendritic cells (DCs). We hereby reviewed the immunoregulatory effects of CHM on the maturation, cytokine production and function of DCs. This should help to shed light on the potential mechanism of CHM to improve the usage and clinical efficacy of CHM.

MATERIALS AND METHODS

Literatures about the effects of CHM on DCs were searched in electronic databases such as Pubmed, Google Scholar and Scopus from 2000 to 2014. 'CHM', 'DC' or 'immune' were used as keywords for the searches. We only reviewed literatures published in English.

RESULTS

Over 600 publications were found about 'CHM&immune' and around 120 literatures about 'CHM&DC' were selected and reviewed in this paper. All publications are backed by preclinical or clinical evidences both in vitro and in vivo. Some CHM and its components promote the maturation, pro-inflammatory cytokine production and function of DCs and as the adjuvant enhance immune responses against tumor and infection. In contrast, other CHM and its components suppress the activation status of DCs to induce regulatory T cells, inhibit allergic and inflammatory responses, ameliorate autoimmune diseases, and prolong the allograft survival. A large body of evidence shows that CHM and its components regulate the activation status of DCs through TLRs, NF-κB, MAPK signaling pathways.

CONCLUSION

This review provides useful information for understanding the mechanism of CHM on the treatment of diseases, which facilitates to improve the efficacy of CHM. Based on the immunoregulatory effects of CHM on DCs, it indicated that some CHM and its components could be use to develop adjuvant to enhance antigen-specific immune responses or tolerogenic adjuvant to generate antigen-specific immune tolerance.

Functions of invariant NK T cells are modulated by TLR ligands and IFN-α

Invariant NK T (iNKT) cells perform numerous immunoregulatory functions. In mice, they express a unique and invariant Vα14-Jα18 rearrangement of α chain in their TCR recognizing glycolipid Ags presented by CD1d. This recognition results in the rapid release of both Th1- and Th2-type cytokines, making them early mediators of the immune response. Owing to their rapid activation and genetic rigidity of their TCR, iNKT cells share characteristics with innate lymphocytes. Therefore, we investigated whether iNKT cells could be induced to express TLRs, a class of pathogen recognition receptor. Mouse iNKT cells were stimulated with anti-CD3 monoclonal Ab and IFN-α, resulting in an increase in the transcription of TLRs 3, 5, 7 and 9, and increased surface expression of TLR3. These cells were subsequently stimulated with TLR ligands, resulting in an increase in the production of IFN-γ, IL-4 and TNF-α. Supernatants from these cells also increased macrophage production of IL-6 and prostaglandin E2, and increased their phagocytic activity and CD80 expression. These supernatants also reduced vesicular stomatitis virus-GFP replication in fibroblasts. This study demonstrates the role of IFN-α in iNKT cell activation, as well as the direct modulatory effects of TLR ligands on iNKT cell function, including antiviral activity.

The role of natural killer cells, gamma delta T-cells and other innate immune cells in spondyloarthritis

PURPOSE OF REVIEW

Natural killer (NK) cells, gamma delta (γδ) T-cells and other innate immune cells are important lymphocyte subsets able both to produce cytokines including the pro-inflammatory cytokine IL-17 and to kill cellular targets. This review describes the features of NK cells, γδ T-cells and other innate immune cells, and outlines the evidence for their potential pathogenic roles in spondyloarthritis (SpA).

RECENT FINDINGS

NK cells and T cells both express receptors that recognize aberrantly folded human leucocyte antigen. This interaction seems to polarize towards a type 17 immunity programme which has been increasingly implicated in SpA pathology. γδ T-cells have also been shown to be polarized towards a type 17 immunity programme in SpA. Gut interactions with the microbiome can influence NK and innate lymphoid immune responses in SpA and other related diseases. A newly identified population of resident lymphoid cells at the enthesis for the first time offers an explanation for the anatomical localization of SpA.

SUMMARY

NK cells, γδ T-cells and other innate immune cells are capable of sharing expression of both transcription factors, including RORγt, and cell surface receptors, such as the killer immunoglobulin-like receptors. There is increasing genetic and functional evidence that they contribute to the RORγt-driven inflammatory type 17 immune responses, and they may link gut inflammation and joint pathology in SpA.