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Itakura A.,Iwaki Meisei University | Itakura A.,Hamamatsu University School of Medicine | Ikutani M.,University of Toyama | Takatsu K.,University of Toyama | And 2 more authors.
International Archives of Allergy and Immunology | Year: 2013

Background: Elicitation of contact hypersensitivity requires antigen-specific immunoglobulin M (IgM) antibodies that trigger recruitment of effector T cells to the local tissue. These antigen-specific IgM antibodies are produced by B-1-like 'initiator B cells'. In this study, we compared susceptibility to hapten-induced contact hypersensitivity between BALB/c and C57BL/6 mice. Methods: BALB/c and C57BL/6 mice were sensitized by painting oxazolone onto the skin and were challenged on the ears with the same hapten on day 4. Ear thickness and serum hapten-specific IgM levels were measured at 24 h post-challenge. Peritoneal cells were harvested and the numbers of B cell subpopulations were counted. Interleukin (IL)-5 was intraperitoneally injected into BALB/c and C57BL/6 mice, and the change in numbers of B cell subpopulations and serum IgM levels was monitored. Results: Oxazolone induced stronger ear swelling and specific IgM responses in BALB/c mice than in C57BL/6 mice. BALB/c mice had higher numbers of peritoneal B-1 cells than C57BL/6 mice at steady state. IL-5 injection increased the number of peritoneal B-1 cells and serum IgM levels more significantly in BALB/mice than in C57BL/6 mice. Conclusions: BALB/c mice exhibit higher susceptibility to hapten-induced contact hypersensitivity than C57BL/6 mice, most likely because they have a higher number of B-1 cells, leading to massive production of hapten-specific IgM antibodies upon contact sensitization. The differences in the number of B-1 cells and IgM responses between the two strains of mice may be attributed to the difference in responsiveness of B-1 cells to IL-5. © 2013 S. Karger AG, Basel.

Watanabe Y.,University of Toyama | Nagai Y.,University of Toyama | Takatsu K.,University of Toyama | Takatsu K.,Toyama Prefectural Institute for Pharmaceutical Research
Nutrients | Year: 2013

Obesity-associated chronic tissue inflammation is a key contributing factor to type 2 diabetes mellitus, and a number of studies have clearly demonstrated that the immune system and metabolism are highly integrated. Recent advances in deciphering the various immune cells and signaling networks that link the immune and metabolic systems have contributed to our understanding of the pathogenesis of obesity-associated inflammation. Other recent studies have suggested that pattern recognition receptors in the innate immune system recognize various kinds of endogenous and exogenous ligands, and have a crucial role in initiating or promoting obesity-associated chronic inflammation. Importantly, these mediators act on insulin target cells or on insulin-producing cells impairing insulin sensitivity and its secretion. Here, we discuss how various pattern recognition receptors in the immune system underlie the etiology of obesity-associated inflammation and insulin resistance, with a particular focus on the TLR (Toll-like receptor) family protein Radioprotective 105 (RP105)/myeloid differentiation protein-1 (MD-1). © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Sasaki S.,University of Toyama | Nagai Y.,University of Toyama | Yanagibashi T.,University of Toyama | Watanabe Y.,University of Toyama | And 6 more authors.
Molecular Immunology | Year: 2012

MD-1 is a secreted protein that forms a complex with radioprotective 105 (RP105) and this complex plays a crucial role in lipopolysaccharide (LPS) recognition by B cells. Disease progression is known to improve in RP105-deficient lupus-prone MRLlpr/lpr mice. Furthermore, a soluble form of the homologous MD-2 protein is present in the plasma of septic patients and can opsonize gram-negative bacteria in cooperation with Toll-like receptor (TLR) 4. We have now established a flow cytometry-based assay to detect the soluble form of murine MD-1 (sMD-1) and explored potential roles in autoimmunity. The assay was quantitative and validated with sera from MD-1-deficient mice. Interestingly, heat-inactivated murine serum diminished the ability of sMD-1 to bind RP105. The sMD-1 was secreted by bone marrow-derived macrophages from C57BL/6 mice. Autoimmune prone MRLlpr/lpr mice had higher levels of sMD-1 than control MRL+/+ mice, and levels markedly increased with disease progression. Expression of MD-1 but not MD-2 mRNA increased with age in the liver and kidney of MRLlpr/lpr mice. Finally, immunohistochemical analyses revealed that MD-1 was present in infiltrated macrophages within perivascular lesions of the MRLlpr/lpr kidney. This correlation suggests that sMD-1 may contribute to pathogenesis in this autoimmune disease model. © 2011 Elsevier Ltd.

Takatsu K.,Toyama Prefectural Institute for Pharmaceutical Research
Frontiers in Immunology | Year: 2014

This is a perspective based on the paper "Cloning of complementary DNA encoding T cell replacing factor and identity with B cell growth factor II", by Kinashi T, Harada N, Severinson E, Tanabe T, Sideras P, Konishi M, Azuma C, Tominaga A, Bergstedt-Lindqvist S, Takahashi M, Matsuda F, Yaoita Y, Takatsu K, and Honjo, T. Nature (1986) 32(6092): 70-3. We have been interested in understanding the molecular basis of T-B cell cooperation for antibody formation. Although many investigators had described a number of different soluble factors that appeared to have biological relevance to T-B cell interactions, molecular basis of such active substances remained unknown for a long period of time. In this perspective, I will briefly summarize the history of the initial discovery of T cell-replacing factor/B cell growth factor II that appeared to be involved in B-cell growth and differentiation, and outline the discovery and characterization of interleukin-5. Studies of interleukin-5 have provided strong evidence that a single cytokine exerts a variety of activities on diverse target cells. © 2014 Takatsu.

Fujisaka S.,University of Toyama | Usui I.,University of Toyama | Ikutani M.,University of Toyama | Aminuddin A.,University of Toyama | And 8 more authors.
Diabetologia | Year: 2013

Aims/hypothesis: As obesity progresses, adipose tissue exhibits a hypoxic and inflammatory phenotype characterised by the infiltration of adipose tissue macrophages (ATMs). In this study, we examined how adipose tissue hypoxia is involved in the induction of the inflammatory M1 and anti-inflammatory M2 polarities of ATMs. Methods: The hypoxic characteristics of ATMs were evaluated using flow cytometry after the injection of pimonidazole, a hypoxia probe, in normal-chow-fed or high-fat-fed mice. The expression of hypoxia-related and inflammation-related genes was then examined in M1/M2 ATMs and cultured macrophages. Results: Pimonidazole uptake was greater in M1 ATMs than in M2 ATMs. This uptake was paralleled by the levels of inflammatory cytokines, such as TNF-α, IL-6 and IL-1β. The expression level of hypoxia-related genes, as well as inflammation-related genes, was also higher in M1 ATMs than in M2 ATMs. The expression of Il6, Il1β and Nos2 in cultured macrophages was increased by exposure to hypoxia in vitro but was markedly decreased by the gene deletion of Hif1a. In contrast, the expression of Tnf, another inflammatory cytokine gene, was neither increased by exposure to hypoxia nor affected by Hif1a deficiency. These results suggest that hypoxia induces the inflammatory phenotypes of macrophages via Hif1a-dependent and -independent mechanisms. On the other hand, the expression of inflammatory genes in cultured M2 macrophages treated with IL-4 responded poorly to hypoxia. Conclusions/interpretation: Adipose tissue hypoxia induces an inflammatory phenotype via Hif1a-dependent and Hif1a-independent mechanisms in M1 ATMs but not in M2 ATMs. © 2013 Springer-Verlag Berlin Heidelberg.

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