Results are expressed as mean SEM

Results are expressed as mean SEM. 0.01) lower response to MCh throughout the doseCresponse curve compared to the sensitized and challenged = 12), challenged-only = 12), sensitized and challenged = 12), and challenged-only = 12). ?, 0.05 compared with 0.05 compared with = 8), sensitized and challenged = 8), challenged-only = 8), challenged-only = 8). ?, 0.05 compared with = 12), sensitized and challenged = 12), challenged-only = 12), and sensitized and challenged = 12). Results are expressed as mean SEM. ?, 0.05 compared with all other groups; #, 0.05 compared with = 10) showed no decrease in BAL total cell counts (mean SEM; 163 35 103 cells) or lymphocyte (28 9 103 cells) and eosinophil (98 23 103 cells) numbers compared with the sensitized and challenged control mice (= 10; 175 53, 35 12, and 115 32 103 cells, respectively). In addition, sensitized and challenged = 10), sensitized and challenged = 10), challenged-only = 10), and challenged-only = 10). (and = 8), and sensitized and challenged mice treated with systemic (?, light gray bars, = 8) or nebulized (, dark gray bars, = 8) control Ab, challenged-only mice (, white bars, = 8), sensitized and challenged mice treated with systemic (?, dotted bars, = 8) or nebulized (, hatched bars, = 8) anti-fB mAb. Mean SEM are given. ?, 0.05 compared with challenged, anti-fB i.p., and anti-fB inhal-treated mice. #, 0.05 compared with challenged-only mice. (= 8), challenged-only = 8), treatment of sensitized and challenged = 8). Mean SEM are given. ?, 0.05 compared with all other groups; #, 0.05 compared with challenged-only mice. As shown in Fig. 4= 8). Discussion A number of studies have suggested that activation of complement occurs after allergen exposure of sensitized hosts (1, 2), and an increasing number of studies using either genetically deficient animals (1, 3, 4, 14) or complement inhibitors (6, 7, 15) have shown that complement activation and generation of complement split products (C3a and C5a) contribute to the development of allergic airway disease. Currently, it is not known which pathway of complement dominates after allergen exposure, and all three (classical, alternative, and lectin pathways) could contribute to complement activation after allergen exposure (9). In the present study we confirmed that complement activation after sensitization and challenge does indeed occur as demonstrated by the elevation of C3a desArg levels in BAL fluid and immunostaining for C3 deposition in the lungs. Evidence for complement activation was markedly reduced in sensitized and challenged and (34). This antibody also has been Isorhynchophylline shown to effectively protect mice from antiphospholipid-induced fetal injury (34). In the present study, the antibody was administered either systemically or locally into the lung by nebulization, which has been shown to be an effective route for administration of other complement inhibitors (7). Indeed, C57BL/6 mice treated after sensitization but during the challenge phase with either systemic or local anti-fB showed a significant decrease in AHR and an inhibition of airway inflammation and eosinophils in the Isorhynchophylline airways and the lung tissue. In addition, the number of goblet cell was reduced. These results are similar to studies that used complement inhibitors that affect both the classical and alternative pathways and block the development of a late airway response (6) and AHR (7). The mechanism of activation of the alternative pathway after allergen exposure is unclear. The alternative pathway can be activated on the surface of pathogens that have neutral- or positive-charge characteristics and do not express or contain complement inhibitors. This phenomenon is caused by a process termed tickover of C3 that occurs spontaneously, involves the interaction of conformationally altered C3 with factor B, and results in the fixation of active C3b on pathogens Isorhynchophylline or other surfaces (20). Further potential pathways for activation include antibodies that block endogenous regulatory mechanisms (35), reduction (36C40), or dysfunction (41, 42) of regulatory proteins. In addition, the alternative pathway is CR2 activated by a mechanism, the amplification loop, when C3b that is deposited onto targets via the classical or lectin pathways then binds factor B (20). Interestingly, there have been several recent reports showing a critical role for the alternative pathway in different models Isorhynchophylline of antibody-mediated disease that have previously been associated with classical pathway activation (43C47). In allergic airway disease it has been proposed that antigenic epitopes on the surface of the allergen might directly activate the alternative pathway Isorhynchophylline (9). However, at this time further studies are needed to identify the mechanism(s) underlying alternative pathway activation after.