2a). Treatment with anti-IgE mAb inhibited the increased level of endogenous OVA-specific IgE in serum, but not OVA-specific IgG1, and a biphasic increase in airway resistance at the fourth challenge. Furthermore, a biphasic increase in airway resistance, airway hyper-responsiveness to methacholine, OVA-specific IgE and IgG1 production, and infiltrations by neutrophils and eosinophils in the lungs at the seventh challenge were suppressed by treatment; airway remodelling, such as goblet cell hyperplasia and sub-epithelial fibrosis, was also reduced. In addition, the production of interleukin-17A, interleukin-33 and CXCL1 in the lungs related to these IgE-mediated responses was decreased by treatment. Collectively, we found that the mechanism leading to the exacerbation of allergic asthma is closely related to IgE/antigen-mediated enhancement of IgE production, suggesting that this may create a vicious circle leading to the chronic status in asthmatic patients having levels of antigen-specific IgE ready to form complexes with antigen. 005 and ** 001 compared with OE-1 (7th) + rat IgG1 group. Treatment with anti-IgE mAb and anti-Fc 005 compared with OE-1 (4th) + rat IgG1 group. In addition, on days C 2, C 1 and 0, a dose (10 g/mouse) of anti-FcmAb (Mar-1, hamster IgG; BioLegend, San Diego, CA) or hamster IgG was administered intraperitoneally twice a day to mice sensitized with OE-1 ( Fig. 2a). It has been reported that mast cells and basophils in the lungs of a murine model of asthma were depleted by treatment with Mar-1 by about 70%, and the depletion was sustained for 7 days.20,21 Open in a separate window Figure 2 Effect of anti-Fc 005 compared with OE-1 (4th) + rat IgG1 group. Measurement of OVA-specific IgE and IgG1 in serumLevels of OVA-specific IgE and IgG1 antibodies in serum were AT-1001 measured by ELISA, as described previously.14 Serum samples were collected 24 hr after the fourth (day 9) or seventh (day 16) antigen challenge in IgE-sensitized mice. OVA-specific IgE antibody was detected using plates coated with anti-mouse IgE antibody and adding biotin-labelled OVA. StreptavidinChorseradish peroxidase was added, the plate was developed with 3,3,5,5-tetramethylbenzidine, and measurements were made at 450 nm using a microplate reader after stopping the reaction with sulphuric acid. Values for serum OVA-specific IgE (1 : 5) are expressed as absorbance units. Ovalbumin-specific IgG1 was detected using plates coated with OVA and adding alkaline phosphate-conjugated anti-mouse IgG1. The plates were developed with for 10 min at 4. The levels of IL-4, IL-5, IL-13, IL-33, CXCL1 (R&D Systems, Minneapolis, MN) and IL-17 (BioLegend) in supernatants of lung homogenates were measured using quantitative colorimetric sandwich ELISA kits. Statistical analysesData are shown as the mean SEM. Statistical analyses between the two groups were performed using Student’s 005 was considered significant. Results Effect of anti-IgE mAb on IgE-mediated biphasic increase in airway resistance at the fourth challenge We have previously found that the level of antigen-specific IgE at the fourth and seventh antigen challenges in IgE-sensitized mice was AT-1001 higher than that in non-sensitizedchallenged mice; additionally, the levels significantly increased over the level of injection of OE-1 alone without antigen challenges.14 Furthermore, the fourth and seventh challenges caused a biphasic increase in airway resistance.14,16,17 First, we examined whether the depletion of endogenous IgE using anti-IgE mAb reduced the biphasic increase in airway resistance at the fourth challenge. OVA-specific IgE and IgG1 in the serum of mice sensitized with OE-1 were significantly AT-1001 increased 24 hr after the fourth challenge (day Rabbit Polyclonal to SCN4B 9) compared with non-sensitizedCchallenged mice; treatment with anti-IgE mAb significantly inhibited OVA-specific IgE in serum, but not OVA-specific IgG1 (Fig. ?(Fig.1b).1b). Furthermore, the fourth challenge induced early-phase and late-phase increased airway resistance in IgE-sensitized mice; the biphasic increase in airway resistance was suppressed by treatment with anti-IgE mAb (Fig. ?(Fig.11c). Effect of anti-Fc 005 compared with OE-1 (7th) + rat IgG1 group. Effect of anti-IgE mAb on IgE-mediated cytokine and chemokine production at the seventh challenge We have reported that a biphasic increase in airway resistance and AHR was induced via neutrophilic inflammation associated with ELR+ chemokines such as CXCL1 induced by IL-33 and IL-17A in IgE-sensitized mice;15C17 furthermore, airway remodelling was related to the expression of IL-33.15 Therefore, we examined the effect of anti-IgE mAb on cytokine and chemokine production. The levels of IL-4, IL-5, IL-13, IL-17A, IL-33 and CXCL1 in the lung 24 hr after the seventh challenge in IgE-sensitized mice were greater than in non-sensitizedCchallenged mice (Fig. ?(Fig.5).5). Treatment with anti-IgE mAb at the fourth challenge inhibited the production of IL-17A, IL-33 and CXCL1 at the seventh challenge in IgE-sensitized mice; furthermore, T helper type 2 cytokines such as IL-5 and IL-13, but not.