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Propolis is a resinous mixture produced by honey bees that contains cinnamic acid derivatives and flavonoids. Although propolis has been reported to inhibit mast cell functions and mast cell-dependent allergic responses, the effect of propolis on basophil biology remains unknown. This study aimed to investigate the inhibitory effect of propolis on FcεRI-mediated basophil activation.

The family of signal-transducing adapter proteins (STAPs) has been reported to be involved in a variety of intracellular signaling pathways and implicated as transcriptional factors. We previously cloned STAP-2 as a c-Fms interacting protein and explored its effects on chronic myeloid leukemia (CML) leukemogenesis. STAP-2 binds to BCR-ABL, upregulates BCR-ABL phosphorylation, and activates its downstream molecules. In this study, we evaluated the role of STAP-1, another member of the STAP family, in CML pathogenesis. We found that the expression of STAP-1 is aberrantly upregulated in CML stem cells (LSCs) in patients’ bone marrow. Using experimental model mice, deletion of STAP-1 prolonged the survival of CML mice with inducing apoptosis of LSCs. The impaired phosphorylation status of STAT5 by STAP-1 ablation leads to downregulation of antiapoptotic genes, Bcl-2 and Bcl-xL. Interestingly, transcriptome analyses indicated that STAP-1 affects several signaling pathways related to BCR-ABL, JAK2, and PPARγ. This adapter protein directly binds to not only BCR-ABL, but also STAT5 proteins, showing synergistic effects of STAP-1 inhibition and BCR-ABL or JAK2 tyrosine kinase inhibition. Our results identified STAP-1 as a regulator of CML LSCs and suggested it to be a potential therapeutic target for CML.

The reported prevalences of IgG autoantibodies (AAbs) to FcεRIα and IgE in sera from patients with chronic spontaneous urticaria (CSU) have varied, and these AAbs are also often observed in healthy control subjects. Regarding the histamine release activity of purified IgG from patients with CSU, the number of examined patients has been small. Thus, we sought to determine the prevalence and FcεRI crosslinking ability of these AAbs in a large number of patients with CSU and non-atopic control (NC) subjects.

Although rodent decidual mast cells (MCs) reportedly play an important role in implantation and placenta formation, the characterization of human decidual MCs has been not well clarified. The aims of this study were to investigate the distribution and characteristics of MCs in human decidua and to establish a culture system for decidua-derived MCs.

Neural pathways are thought to be directly involved in the pathogenesis of rheumatoid arthritis (RA). Although synovial mast cells (MCs) are activated by substance P (SP), the role of MCs in neural pathways in RA remains unknown. The aims of this study were to investigate 1) whether tachykinins are produced by synovial MCs and whether production differs in RA and osteoarthritis (OA) patients, and 2) what is the responsible receptor for SP in synovial MCs.

Interleukin (IL)-17A plays a pivotal role in the pathogenesis of rheumatoid arthritis (RA). The expression of IL-17A in synovial mast cells (MCs) in RA and osteoarthritis (OA) has been reported, but the frequencies of IL-17A expression in synovial MCs have varied. The aim of this study was to investigate whether IL-17A expression is upregulated in human synovial MCs in RA and to elucidate the mechanism of IL-17A expression in synovial MCs.

Atopic dermatitis (AD) is a chronic inflammatory skin disease. Here, we show that phospholipase C-β3 (PLC-β3)-deficient mice spontaneously develop AD-like skin lesions and more severe allergen-induced dermatitis than wild-type mice. Mast cells were required for both AD models and remarkably increased in the skin of Plcb3−/−mice because of the increased Stat5 and reduced SHP-1 activities. Mast cell-specific deletion of Stat5gene ameliorated allergen-induced dermatitis, whereas that of Shp1gene encoding Stat5-inactivating SHP-1 exacerbated it. PLC-β3 regulates the expression of periostin in fibroblasts and TSLP in keratinocytes, two proteins critically involved in AD pathogenesis. Furthermore, polymorphisms in PLCB3, SHP1, STAT5A, and STAT5Bgenes were associated with human AD. Mast cell expression of PLC-β3 was inversely correlated with that of phospho-STAT5, and increased mast cells with high levels of phospho-STAT5 were found in lesional skin of some AD patients. Therefore, STAT5 regulatory mechanisms in mast cells are important for AD pathogenesis.

Ag-dependent activation of IgE-bearing mast cells is a critical first step in immediate hypersensitivity and other allergic responses. Recent studies have revealed Ag-independent effects of monoclonal mouse IgE molecules on mast cell survival and activation. However, no studies have been performed on the effects of polyclonal IgE molecules. Here, we tested whether polyclonal mouse and human IgE molecules affect survival and cytokine production in mast cells.

Antigen‐dependent activation of IgE‐bound mast cells is critical for immediate hypersensitivity and other allergic disorders. Recent studies have revealed the effects of monomeric IgEs on mast cell survival and activation. Furthermore, IgE molecules exhibit a wide range of heterogeneity in the ability to induce mast cell activation in the absence of antigen. Highly cytokinergic (HC) IgEs can induce a variety of activation events including cell survival, degranulation, cytokine production, and migration, whereas poorly cytokinergic (PC) IgEs can do so inefficiently. Here, we show that culture of bone marrow cells in the presence of monomeric IgEs results in an increased number of mast cells compared with cultures grown without IgE. Furthermore, time in culture required to generate ≥80% pure mast cells is decreased. IgE molecules can directly influence mast cell progenitors to differentiate into mast cells. mRNA expression of several mast cell proteases and mast cell‐related transcription factors is higher in mast cells cultured with an HC IgE than those cultured with a PC IgE or without IgE. Expression of early growth response factor‐1, a transcription factor that is involved in the production of TNF‐α in mast cells, is enhanced in cultures containing high and low concentrations of HC IgE and a high concentration of PC IgE. Consistent with this, expression of TNF‐α is higher in mast cells cultured with HC IgE than PC IgE. Therefore, our results suggest that monomeric IgEs, especially HC IgEs, not only promote mast cell development but also modulate the mast cell phenotype.

Human mast cells (MCs) were classified into at least two subtypes, i.e.,tryptase- and chymase-positive MCs (MCtc)and tryptase-only-positive MCs (MCt).However, differences in global molecular expression between these subtypes are unknown.

Mast cells express high-affinity IgE receptors (FcεRI) on their surface and can be activated to secrete a variety of biologically active mediators by cross-linking of receptor-bound IgE. Recent studies in animal models indicate that mouse mast cells may play a protective role in host defense against bacteria through the production of tumor necrosis factor-α, mainly as a result of Toll-like receptor (TLR) 4- or CD48-mediated activation. Moreover, several recent observations in animal models have indicated that mast cells may also play a pivotal role in coordinating the early phases of autoimmune diseases, particularly those involving auto-antibodies. We recently identified functional TLR4 and FcγRI on human mast cells, in which their expression had been upregulated by interferon-γ. We compared each of the receptor-mediated gene expression profiles with the FcεRI-mediated gene expression profile using high-density oligonucleotide probe arrays and discovered that human mast cells may modulate the immune system in a receptor-specific manner.

Rodent mast cells (MCs) are reported to play a pivotal role in both innate and adaptive immunity. However, there is so far no evidence that human MCs are involved in innate immunity. We found that a functional Toll-like receptor 4 (TLR4) was expressed on human MCs when it was up-regulated by interferon γ (IFN-γ). To systematically explore how human MCs modulate the immune system following TLR4-mediated activation and FcϵRI aggregation, we used high-density oligonucleotide probe arrays (GeneChip) to compare the lipopolysaccharide (LPS)-induced gene expression profile with the IgE/anti-IgE-mediated profile in MCs. Both a shared core response, and LPS- or anti-IgE-specific programs of gene expression were observed in MCs. Furthermore, MCs exhibited an antiviral response gene program in response to IFN-γ, and LPS sustained that expression. Compared with the LPS-stimulated gene expression profile of human peripheral blood mononuclear cells, LPS-stimulated MCs specifically induced a subset of genes that included a Th2 cytokine and chemokines that recruit Th2 cells and eosinophils. These results reveal that human MCs express tailored pathogen- and antigen-specific immune responses and that human MCs may play important roles in innate and adaptive immunity.(Blood. 2003;102:2547-2554)

Rodent mast cells (MCs) are reported to play a pivotal role in both innate and adaptive immunity. However, there is so far no evidence that human MCs are involved in innate immunity. We found that a functional Toll-like receptor 4 (TLR4) was expressed on human MCs when it was up-regulated by interferon γ (IFN-γ). To systematically explore how human MCs modulate the immune system following TLR4-mediated activation and FcϵRI aggregation, we used high-density oligonucleotide probe arrays (GeneChip) to compare the lipopolysaccharide (LPS)-induced gene expression profile with the IgE/anti-IgE-mediated profile in MCs. Both a shared core response, and LPS- or anti-IgE-specific programs of gene expression were observed in MCs. Furthermore, MCs exhibited an antiviral response gene program in response to IFN-γ, and LPS sustained that expression. Compared with the LPS-stimulated gene expression profile of human peripheral blood mononuclear cells, LPS-stimulated MCs specifically induced a subset of genes that included a Th2 cytokine and chemokines that recruit Th2 cells and eosinophils. These results reveal that human MCs express tailored pathogen- and antigen-specific immune responses and that human MCs may play important roles in innate and adaptive immunity.(Blood. 2003;102:2547-2554)

Differentiation of human T cells into T helper (Th)1 and Th2 cells is vital for the development of cell-mediated and humoral immunity, respectively. However, the precise mechanism responsible for the Th1 cell differentiation is not fully clarified. We have studied the expression and function of Txk, a member of the Tec family of nonreceptor tyrosine kinases. We found that Txk expression is restricted to Th1/Th0 cells with IFN-γ producing potential. Txk transfection of Jurkat T cells resulted in a several-fold increase of IFN-γ mRNA expression and protein production; interleukin (IL)-2 and IL-4 production were unaffected. Antisense oligodeoxynucleotide of Txk specifically inhibited IFN-γ production of normal peripheral blood lymphocytes, antigen-specific Th1 clones, and Th0 clones; IL-2 and IL-4 production by the T cells was unaffected. Txk cotransfection led to the enhanced luciferase activity of plasmid (p)IFN-γ promoter/enhancer (pIFN-γ[-538])-luciferase–transfected Jurkat cells upon mitogen activation. Txk transfection did not affect IL-2 and IL-4 promoter activities. Thus, Txk specifically upregulates IFN-γ gene transcription. In fact, Txk translocated from cytoplasm into nuclei upon activation and transfection with a mutant Txk expression plasmid that lacked a nuclear localization signal sequence did not enhance IFN-γ production by the cells, indicating that nuclear localization of Txk is obligatory for the enhanced IFN-γ production. In addition, IL-12 treatment of peripheral blood CD4+ T cells enhanced the Txk expression, whereas IL-4 treatment completely inhibited it. These results indicate that Txk expression is intimately associated with development of Th1/Th0 cells and is significantly involved in the IFN-γ production by the cells through Th1 cell–specific positive transcriptional regulation of the IFN-γ gene.

Ichii: Celgene K.K.: Speakers Bureau; Kowa Pharmaceutical Co.,LTD.: Speakers Bureau; Novartis Pharma K.K.: Speakers Bureau. Shibayama:Takeda Pharmaceutical Co.,LTD.: Honoraria, Research Funding; Mundipharma K.K.: Honoraria, Research Funding; Jansen Pharmaceutical K.K: Honoraria; Ono Pharmaceutical Co.,LTD: Honoraria, Research Funding; Fujimoto Pharmaceutical: Honoraria, Research Funding; Novartis Pharma K.K.: Honoraria, Research Funding; Bristol-Meyer Squibb K.K: Honoraria, Research Funding; Celgene K.K.: Honoraria, Research Funding. Oritani:Novartis Pharma: Speakers Bureau. Kanakura:Alexion Pharmaceuticals, Inc.: Consultancy, Honoraria, Research Funding.

Ichii: Celgene K.K.: Speakers Bureau; Kowa Pharmaceutical Co.,LTD.: Speakers Bureau; Novartis Pharma K.K.: Speakers Bureau. Shibayama:Fujimoto Pharmaceutical: Honoraria, Research Funding; Takeda Pharmaceutical Co.,LTD.: Honoraria, Research Funding; Celgene K.K.: Honoraria, Research Funding; Jansen Pharmaceutical K.K: Honoraria; Ono Pharmaceutical Co.,LTD: Honoraria, Research Funding; Novartis Pharma K.K.: Honoraria, Research Funding; Mundipharma K.K.: Honoraria, Research Funding; Bristol-Meyer Squibb K.K: Honoraria, Research Funding. Oritani:Novartis Pharma: Speakers Bureau. Kanakura:Alexion Pharmaceuticals, Inc.: Consultancy, Honoraria, Research Funding.

Chronic myelogenous leukemia (CML) is a clonal myeloproliferative disorder caused by hematopoietic stem cells expressing the BCR-ABL fusion oncoprotein, which constitutively activates multiple signal transduction pathways such as mitogen-activated protein kinase, phosphatidylinositol 3-kinase/Akt, and Janus kinase/signal transducer and activator of transcription (JAK/STAT). Although tyrosine kinase inhibitor (TKI) therapy results in dramatic clinical success, studies have shown that TKIs are unable to eradicate leukemic stem cells (LSCs). Several key signaling molecules and pathways have been proposed to regulate the survival of CML LSCs in the presence of TKI; however, the details remain unclear. It is necessary to elucidate the mechanisms that maintain LSCs to better understand the pathogenesis of CML and develop new treatment approaches.

Graft-versus-host-disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the most frequent complication and one of the major causes of non-relapse mortality. However, its pathogenesis has not yet been fully understood. We cloned signal-transducing adaptor protein (STAP)-2 as a c-fms binding protein from a fetal liver library in 2003. The family that contains STAP-1 and STAP-2 has a pleckstrin homology (PH) and Src-homology 2 (SH2)-like domains, suggesting that this adapter protein functions as an immune and inflammatory regulator. Indeed, STAP-2 regulates adhesion and chemotaxis in T cells (Sekine et al., J Immunol. 2009). In this study, we aimed to elucidate the roles of STAP family in GVHD.

All lineages of blood cell production from hematopoietic stem cells (HSC) are maintained for an entire lifetime. That is consistent under homeostatic condition, while hematopoiesis is changed in response to various types of stress, including infections and aging. It has been reported that hematopoietic stem and progenitor cells (HSPC) are targets of pathogen products and danger signals. After the exposure to Gram-negative lipopolysaccharide (LPS) that is the ligand of Toll-like receptor (TLR) 4, HSC enter cell-cycle and differentiate into myeloid lineage cells while B lymphopoiesis is suppressed. Although the regulation of hematopoiesis by HSC is well studied, many questions still remain regarding how progenitors contribute the response to hematopoietic demands. Signal-transducing adaptor protein-2 (STAP-2) was cloned as a c-fms/M-CSFR interacting protein in 2003, and the interaction with a variety of signaling or transcriptional molecules such as STAT5, MyD88 and IκB kinase (IKK) in macrophages or T cells has been reported. The function as an adaptor protein in various cell types and signaling pathways, and its ubiquitous expression promoted us to investigate the effect of STAP-2 on HSPC under hematopoietic stress using gene-modified mice.

Chronic myelogenous leukemia (CML) is a clonal myeloproliferative disorder that is caused by hematopoietic stem cells expressing the BCR-ABL fusion oncoprotein, which constitutively activates multiple signal transduction pathways, regulates cell proliferation, and is involved in apoptosis. Since the approval of tyrosine kinase inhibitors for the management of CML, treatments have been dramatically improved. However, some proportion of patients still cannot achieve an optimal response, and the discovery of novel targets for CML treatment is required. In this study, we showed that the signal-transducing adaptor protein (STAP) family is a potent therapeutic target for CML. STAP-1, one of the two related proteins, is a c-kit interacting protein that was cloned from a hematopoietic stem cell cDNA library in 2000. Three years later, we cloned STAP-2 as a c-fms interacting protein from a fetal liver library. These proteins share 33% of overall amino acid identity, and have a pleckstrin homology (PH) and Src-homology 2 (SH2) -like domain, which are typical structures of an adaptor protein. Recently, we have reported that STAP-2 binds to BCR-ABL via its SH2-like domain and enhances BCR-ABL activity (Sekine et al. Oncogene 2012), while the function of STAP-1 is largely unknown. In this study, we aimed to elucidate the roles of STAP family members in CML.

A large body of evidence has demonstrated that treatment with omalizumab is clinically effective for the management of moderate to severe allergic asthma, emphasizing the importance of IgE in the pathogenesis of allergic asthma. We hypothesized that IgE accelerates FcεRI-mediated responsiveness of “immature” human mast cells (MCs) and that omalizumab downregulates the acceleration.