Despite the evidence for the role of inflammation in cancer initiation, promotion, and progression, the precise mechanism by which the inflammation within tumor is orchestrated by inflammatory cells remains to be determined. Here IntroductionChronic inflammation, a "promoting force" in the tumor microenvironment, has long been known to be commonly braided with the initiation, promotion, and progression of tumorigenesis. [1][2][3][4][5] To date, however, it is still incompletely understood how the inflammation in the tumor microenvironment is orchestrated by inflammatory cells. Recently, mast cells were highlighted as not only a major participator but also an important regulator of inflammation, 6,7 and their accumulation in tumors has also been well documented, [8][9][10][11][12][13] implying that mast cells may possibly play an important role in orchestrating the inflammation in tumors.The tumor microenvironment is regarded as a "smoldering" inflammation site in which a lot of cytokines, chemokines, and enzymes mediate the inflammatory process and drive malignant progression. 14,15 Among them, TNF-␣, IL-6, VEGF, iNOS, Cox-2, and MMP-9 are of particular interest. [15][16][17][18] Coincidentally, all of them can be produced by mast cells. However, the tumor microenvironment is also characterized by its immunoediting from immunosurveillance to immunosuppression. 19 Mast cells have been found to play a critical role in the suppression of immune reactions. 20 They not only produce inhibitory cytokine IL-10, 21 but they also are essential for the immune tolerance mediated by regulatory T (Treg) cells. 22 Thus, mast cell infiltration into tumor may possibly remodel tumor microenvironment and profoundly influence tumor behavior by participating and regulating inflammatory and immune reactions. However, although some studies have shown that mast cells promote tumor angiogenesis and tumor growth because of their properties as inflammatory cells, [23][24][25] the roles of mast cells in tumor progression have been incompletely understood so far. Several key questions remain unclear, especially how mast cells are recruited into the tumor site and whether they can remodel the tumor microenvironment.Mast cell migration to the tumor site and the following activation may be the prerequisite for their promoting effect on tumors. In this regard, stem cell factor (SCF) is possibly involved, because SCF triggers the c-Kit signaling pathway for the differentiation, migration, maturation, and survival of mast cells. 26 In the present study, we investigated the relation of mast cells and SCF in tumor progression and showed that SCF recruited and activated mast cells, the activated mast cells remodeled the tumor microenvironment by intensifying inflammation and immunosuppression, the tumor cell NF-B and AP-1 activities were augmented, and the suppression of T cells and natural killer (NK) cells was exacerbated in such remodeled microenvironments. These findings provide a new insight into the role of mast cells in tumors and the relati...

IL-17 is a pivotal proinflammatory molecule in asthmatics. However, the cellular source of IL-17 in asthma has not been identified to date. In this study, we report that macrophages rather than Th17 cells are the main producer of IL-17 in allergic inflammation related to asthma. After OVA challenge in a mouse model mimicking allergic asthma, the increased IL-17+ cells in the lung were mainly CD11b+F4/80+ macrophages, instead of T cells or others. Importantly, IL-17+ alveolar macrophages (AMs), but not IL-17+ interstitial macrophages, were significantly increased after allergen challenge. The increase of IL-17+ AMs was not due to the influx of IL-17+ macrophages from circulation or other tissues, but ascribed to the activation of AMs by mediator(s) secreted by IgE/OVA-activated mast cells. Depleting alveolar macrophages or neutralizing IL-17 prevented the initiation of OVA-induced asthma-related inflammation by inhibiting the increase of inflammatory cells and inflammatory factors in bronchoalveolar lavage fluid. Th2 cytokine IL-10 could down-regulate IL-17 expression in alveolar macrophages. The increased IL-17 and the decreased IL-10 in bronchoalveolar lavage fluid were further confirmed in asthmatic patients. These findings suggest that IL-17 is mainly produced by macrophages but not Th17 cells in allergic inflammation related to asthma. Mast cell-released mediators up-regulate the expression of IL-17 by macrophages, whereas IL-10 down-regulates IL-17 expression.

Pregnant women have both the local immune tolerance at the maternal-fetal interface and the systemic immune defense against pathogens. To date, regardless of the extensive investigation on the maternal-fetal immune tolerance, the maintenance of systemic immune defense in pregnant women still remains poorly understood. In the present study, we demonstrate that the immunoregulatory molecule T cell Ig and mucin domain (Tim)-3 plays important roles in innate and adaptive immunity of human pregnancy. During pregnancy, Tim-3 is strikingly up-regulated in peripheral blood of pregnant women, most by monocytes but not by T or B cells. The increased IL-4/STAT6 signaling may contribute to such up-regulation of Tim-3. In turn, the increased Tim-3 enhances not only innate immunity but also Th1-associated immune responses of pregnant women against pathogens. In contrast, our clinical data show that abnormal Tim-3 expression level might be connected to the pregnancy loss. In conclusion, our data show in this study that an immune regulatory molecule Tim-3, by virtue of its up-regulation in innate immune cells in pregnant women, enhances both innate and adaptive immune responses. Nevertheless, the abnormality of Tim-3 in pregnant woman may be deleterious to normal pregnancy.

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Myeloid-derived suppressor cells (MDSCs), a heterogeneous population including myeloid progenitor and immature myeloid cells, are known to inhibit T cell responses. The issue of whether tumour-derived MDSCs regulate the immune response in an asthma environment is currently unclear. Here, we have reported that tumour-derived MDSCs shift the balance back to normal in a Th2-dominant asthmatic environment. In an ovalbumin (OVA)-induced mouse asthma model, injected tumour-derived MDSCs were recruited to the lungs of asthmatic mice by CC chemokine ligand 2 (CCL2). MDSCs transferred into asthmatic mice via i.v. injection suppressed the infiltration of inflammatory cells into the lung, the Th2 cytokine, IL-4, concentration in bronchial lavage fluid and the serum level of OVA-specific IgE. Increased TGF-b1 production in the lung was detected after transfer of MDSCs. The inhibitory effects of MDSCs were reversed upon treatment with an anti-TGF-b1 antibody, suggesting dependence of these activities on TGF-b1. Our findings imply that tumour-derived MDSCs inhibit the Th2 cell-mediated response against allergen in a TGF-b1-dependent manner. Based on the collective results, we propose that asthma may be effectively targeted using a novel MDSC-based cell therapy approach.