(DOCX) Click here for additional data file.(116K, docx) S2 FigInduction of proinflammatory cytokines in the course of degranulation. by mast cell activation in the course of rejection and following tolerance induction [23]. Transient elevation of hepatic histone H1 and circulating anti-histone H1 Ab in the course of rejection is one of important events for overcoming rejection [24], and these data strongly suggest the involvement of histone H1 and corresponding Ab for regulation of mast cell activity in transplant immunology. To further explore underlying mechanism regarding histone H1 and corresponding Ab in mast cells, we shift our focus on mast cell-mediated allergic response in the present study. Allergic rhinitis, which includes pollinosis, is categorized as a type I hyperreactivity and depends on the conversation between antigens and the antigen-specific IgE Ab attached to mast cells [25]. Recently, several studies have detected the induction of nasal HMGB1 in allergic rhinitis [26], chronic rhinosinusitis [27], and upper airway inflammatory diseases [28], suggesting the involvement of nuclear antigens in the induction of allergic responses. In the course of a bona-fide experimental allergen sensitization model upon co-injection with alum adjuvant, the alum causes cell Rabbit Polyclonal to NSG2 death and the subsequent release of host cell DNA mediates allergen-specific Th2 response and IgE production [29]. A recent paper also noted the significance of host cell DNA complexed with core histones, but not linker histone H1, in the initiation of a T cell-intrinsic Th2 cell differentiation by unknown innate immune mechanisms [30]. However, it is unclear about the role of histone H1 in mast cell-mediated type I hyperreactivity. In this study, we show impact of endogenous linker histone H1 around the progression of allergic rhinitis-like nasal symptoms in mice as well as on its positive regulatory role in mast cell degranulation. The therapeutic potential of a newly developed monoclonal Ab (mAb) against a histone H1 peptide mimotope (SSVLYGGPPSAA) referred to as SSV mAb, which is responsible for the immunosuppression of anti-histone H1 mAb [31], was also evaluated. Materials and Methods Ethics statement Our experimental design was reviewed and approved by the Institutional Animal Care and Use Committee in Kaohsiung Chang Gung Memorial Hospital (approval No.: 2014101601). The Committee recognizes that the proposed animal experiment follows the Animal Protection Law by the Council of Agriculture, Executive Yuan, R.O.C. and the guideline shown in the Guide for the Care and Use of Laboratory RQ-00203078 Animals, as promulgated by the Institute of Laboratory Animal Resources, National Research Council, USA. Animals Male Lewis rats and female BALB/c mice were obtained at 5 weeks of age from RQ-00203078 the National Laboratory Animal Breeding and Research Center (Taipei, Taiwan) or Charles River Laboratories (Yokohama, Japan). All animals were maintained under specific pathogen-free animal facilities with water and commercial diet < 0.01 versus IgE only (0 g/ml of histone H1). (B) Exogenous histone H1 enhanced DNP-BSA-induced degranulation of RBL-2H3 cells in a dose-dependent manner. **, < 0.01 versus (IgE + Ag: 0 g/ml of histone H1). (C) Histone H1-targeted SSV mAb ameliorated DNP-BSA-induced degranulation of RBL-2H3 cells in a dose-dependent manner. **, < 0.01 versus (IgE + Ag: 0 g/ml of SSV mAb) or (IgE + Ag: 100 g/ml of isotype IgG1). (D) The extracellular secretion of endogenous histone H1 by DNP-BSA (0.1 and 0.5 g/ml) in BMMCs. Western blot data are representative of three impartial experiments. Calf thymus histone H1 was loaded as a positive control. Enhancement of PCA by histone H1 and inhibition of PCA by corresponding SSV mAb To explore the impact RQ-00203078 of histone H1 on PCA response model of mast cell degranulation, exogenous histone H1 induced mast cell degranulation without DNP-BSA stimulation and further enhanced DNP-BSA-induced degranulation by exogenous histone H1 in a dose-dependent manner (Fig 3). Of note, IgE sensitization may be indispensable for histone H1-mediated induction of mast cell degranulation due to the lack of allergic rhinitis in PBS/Alum-sensitized and histone H1-challenged mice (Fig 2A) and the lack of PCA response in PBS/histone H1-injected ear (Fig 4A). The most probable mechanism of mast cell degranulation by histone H1 must be the autocrine/paracrine effects that histone H1.