Tumor-induced suppression of interferon-γ production and enhancement of interleukin-10 production by natural killer (NK) cells: paralleled to CD4+ T cells

CD1dhiPD-L1hiCD27+ Regulatory Natural Killer Subset Suppresses Atopic Dermatitis

Effector and regulatory functions of various leukocytes in allergic diseases have been well reported. Although the role of conventional natural killer (NK) cells has been established, information on its regulatory phenotype and function are very limited. Therefore, the objective of this study was to investigate the phenotype and inhibitory functions of transforming growth factor (TGF)-β-producing regulatory NK (NKreg) subset in mice with MC903-induced atopic dermatitis (AD). Interestingly, the population of TGF-β-producing NK cells in peripheral blood monocytes (PBMCs) was decreased in AD patients than in healthy subjects. The number of TGF-β⁺ NK subsets was decreased in the spleen or cervical lymph node (cLN), but increased in ear tissues of mice with AD induced by MC903 than those of normal mice. We further observed that TGF-β⁺ NK subsets were largely included in CD1d^hiPD-L1^hiCD27⁺ NK cell subset. We also found that numbers of ILC2s and T_H2 cells were significantly decreased by adoptive transfer of CD1d^hiPD-L1^hiCD27⁺ NK subsets. Notably, the ratio of splenic Treg per T_H2 was increased by the adoptive transfer of CD1d^hiPD-L1^hiCD27⁺ NK cells in mice. Taken together, our findings demonstrate that the TGF-β-producing CD1d^hiPD-L1^hiCD27⁺ NK subset has a previously unrecognized role in suppressing T_H2 immunity and ILC2 activation in AD mice, suggesting that the function of TGF-β-producing NK subset is closely associated with the severity of AD in humans.

Cytokine expression in response to root repair agents

AIM

To evaluate the expression of TNF-α, IL-6, IFN-γ, TGF-β, IL-4, IL-10, RANKL, RANK and OPG on mouse calvarial bone treated with MTA, Geristore^® and Emdogain^® .

METHODOLOGY

Bone wounds were made on the heads of C57BL/6 mice, breaking the periosteum and the cortical surface of the calvaria. Each repair agent was inserted into sectioned Eppendorf microtubes and placed on the bone wound, and soft tissues were sutured. At 14 and 21 days, animals were sacrificed and the treated region was dissected. The calvaria bone was removed, and RNA was extracted. mRNA expression of the aforementioned cytokines was assessed using real-time PCR. Data were analysed by nonparametric methods, including the Mann-Whitney and Kruskal-Wallis tests (P < 0.05).

RESULTS

Following treatment with Emdogain^® and MTA, mRNA expression of RANKL, RANK and OPG increased significantly (P < 0.05) between days 14 to 21. Geristore^® did not alter the basal expression of these mediators during the same period of evaluation. Whilst treatment with Emdogain^® did cause a significant increase in TNF-α mRNA expression between days 14 and 21 (P < 0.05), treatment with MTA did not alter the basal expression of this cytokine at either experimental time point. However, TNF-α mRNA expression was down-regulated significantly at day 21 (P < 0.05) when Geristore^® was applied. A significant increase in the mRNA expression of IL-6, TGF-β, IL-10, IL-4 and IFN-γ was observed with Emdogain^® and MTA treatment between days 14 to 21, whereas Geristore^® reduced significantly the expression of IL-6, TGF-β and IL-4 (P < 0.05).

CONCLUSION

The clinical indication of these repair agents depends on the root resorption diagnosis. Whilst MTA and Emdogain^® induce a pro- and anti-inflammatory response early and late, respectively, Geristore^® was not associated with an inflammatory reaction when compared with both repair agents.

NK-derived IFN-γ/IL-4 triggers the sexually disparate polarization of macrophages in CVB3-induced myocarditis

Coxsackievirus B3 (CVB3) is a common etiology of myocarditis with an increased morbidity and mortality in males. We previously reported that differential polarization of macrophages contributed to sexually dimorphic susceptibility of mice to CVB3-induced myocarditis. However, the underlying kinetics, impetus as well as the molecular mechanism remain unclear. Here, we demonstrated that myocardial macrophages started to polarize at as early as day 5 post CVB3 infection in both genders of BALB/c mice, with M1 phenotype detected in males and M2a phenotype in females, and this trend was further amplified at day 7 when myocarditis reached peak. In addition, we identified that prevailed IFN-γ in males and dominant IL-4 in females were critical myocardial cytokines for the disparate macrophage polarization, which respectively activated JAK1-STAT1 and JAK3-STAT6 pathways. Strikingly, we found that the main source of IFN-γ and IL-4 cytokines in both genders were myocardial infiltrating NK cells, which differentially secreted cytokines in various microenvironments manifested synergistically by sex hormones and CVB3 infection. Consistently, depletion of NK cells significantly impeded the myocardial macrophage polarization in both genders of CVB3-infected mice. Collectively, these data indicated that myocardial NK-derived IFN-γ/IL-4 was critical for the differential polarization of macrophages in CVB3-induced myocarditis via activating JAK1-STAT1 and JAK3-STAT6 pathways respectively. Our study may help understand the mechanism of sexually differential polarization of macrophages and provide clues for the gender bias in CVB3-induced myocarditis.

Natural killer cells in patients with allergic diseases

Natural killer (NK) cells not only exert cytotoxic activity against tumor cells or infected cells but also act to regulate the function of other immune cells through secretion of cytokines and chemokines or cell contact-dependent mechanisms. NK cells are able to polarize in vitro into 2 functional distinct subsets, NK1 or NK2 cells, which are analogous to the T-cell subsets TH1 or TH2. In addition, a regulatory NK cell subset has been described that secretes IL-10, shows antigen-specific T-cell suppression, and suppresses IgE production. Although it has been demonstrated that NK cells play important roles in autoimmunity, cancer, transplantation, and pregnancy, the role of NK cells in allergy has not been extensively discussed. This review aims to discuss our understanding of NK cells and NK cell subsets in allergic inflammation and IgE regulation.

Regulatory NK cells in autoimmune disease

As major components of innate immunity, NK cells not only exert cell-mediated cytotoxicity against tumor cells or infected cells, but also act to regulate the function of other immune cells by secretion of cytokines and chemokines, thus providing surveillance in early defense against viruses, intracellular bacteria and cancer cells. However, the effector function of NK cells must be exquisitely controlled in order to prevent inadvertent attack against self normal cells. The activity of NK cells is defined by integration of signals coming from inhibitory and activation receptors. Inhibitory receptors not only distinguish healthy from diseased cells by recognize self-MHC class I molecules on cell surfaces with "missing-self" model, but also provide an educational signal that generates functional NK cells. NK cells enrich in immunotolerance organ and recent findings of different regulatory NK cell subsets have indicated the unique role of NK cells in maintenance of homeostasis. Once the self-tolerance is broken, autoimmune response may occur. Although data has demonstrated that NK cells play important role in autoimmune disorders, NK cells seemed to act as a two edged weapon and play opposite roles with both regulatory and inducer activity even in the same disease. The precise role and regulatory mechanisms need to be further determined. In this review, we focus on recent research on the association of NK cells and antoimmune diseases, particularly the genetic correlation, the immune tolerance and misrecognition of NK cells, the regulatory function of NK cells, and their potential role in autoimmunity.

Natural killer T cells suppress zymosan A-mediated granuloma formation in the liver by modulating interferon-γ and interleukin-10

Wild-type (WT) and CD1d(-/-) [without natural killer (NK) T cells] mice were treated with zymosan A to induce granuloma formation in the liver. Increased granuloma formation was seen in NKT-less mice on days 7 and 14 after administration. WT mice showed limited granuloma formation, and zymosan A eventually induced NKT cell accumulation as identified by their surface marker (e.g. CD1d-tetramer). Zymosan A augmented the expression of Toll-like receptor 2 on the cell surface of both macrophages and NKT cells. One possible reason for accelerated granuloma formation in NKT-less mice was increased production of interferon- γ (IFN-γ); a theory that was confirmed using IFN-γ(-/-) mice. Also, zymosan A increased interleukin-10 production in WT mice, which suppresses IFN-γ production. Taken together, these results suggest that NKT cells in the liver have the potential to suppress zymosan A-mediated granuloma formation.

Restraint stress modulates virus specific adaptive immunity during acute Theiler's virus infection

Multiple sclerosis (MS) is a devastating CNS disease of unknown origin. Multiple factors including genetic background, infection, and psychological stress affect the onset or progression of MS. Theiler's murine encephalomyelitis virus (TMEV) infection is an animal model of MS in which aberrant immunity leads to viral persistence and subsequently results in demyelination that resembles MS. Here, we examined how stress during acute TMEV infection altered virus-specific cell mediated responses. Using immunodominant viral peptides specific for either CD4(+) or CD8(+) T cells, we found that stress reduced IFN-gamma producing virus-specific CD4(+) and CD8(+) T cells in the spleen and CD8(+) T cells CNS. Cytokine production by cells isolated from the CNS or spleens following stimulation with virus or viral peptides, indicated that stress decreased both type 1 and type 2 responses. Glucocorticoids were implicated in the decreased T cell function as the effects of stress were partially reversed by concurrent RU486 administration but mimicked by dexamethasone. As T cells mediate viral clearance in this model, our data support the hypothesis that stress-induced immunosuppression may provide a mechanism for enhanced viral persistence within the CNS.