2826 Abstracts / Molecular Immunology 46 (2009) 2818–2871 Session 4: Complement in autoimmune and inflammatory dis- eases (6 September, 17:20–19:00) O22 Factor H plays an essential role in the control of airway hyper- responsiveness and eosinophilic pulmonary inflammation in experimental asthma V. Michael Holers a,b,c,d,∗ , Kat Takeda a,b,c,d , Joshua M. Thurman a,b,c,d , Steve Tomlinson a,b,c,d , Viviana P. Ferreira a,b,c,d , Claudio Cortes a,b,c,d , Michael K. Pangburn a,b,c,d , Erwin W. Gelfand a,b,c,d a Department of Medicine, University of Colorado Denver, School of Medicine, Aurora, CO, United States b National Jewish Health, Denver, CO, United States c Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC, United States d Department of Biochemistry, University of Texas Health Sciences Cen- ter, Tyler, TX, United States The alternative pathway has been shown to play an essen- tial role in the development of airway hyperresponsiveness (AHR) and inflammation in a mouse model of asthma. The current study hypothesis is that the inability of factor H to fully control C3 con- vertases following allergen challenge leads to enhanced airway disease. We utilized a recombinant protein that increases the local deposition of the regulatory domain of murine factor H (mu-CR2- fH), or a dominant negative inhibitor that blocks factor H activities (mu-fHSCR19-20). Mu-CR2-fH contains the iC3b/C3d-binding frag- ment of mouse complement receptor 2 (CR2) linked to SCR1-5 of factor H. Mu-fHSCR19-20 blocks factor H binding to target sur- faces and impairs factor H ability to control local C3 activation. In a primary allergen challenge model, C57BL/6 mice were sensi- tized to OVA with alum by intraperitoneal (ip) injection followed by three consecutive days of 1% OVA inhalation. Mice were treated by ip administration of mu-CR2-fH, CR2 alone or vehicle control 2 h prior to each OVA inhalation. In the secondary allergen challenge model, mice were sensitized to OVA, received three consecutive days of 0.2% OVA inhalation one week later, and then two weeks later received ip mu-CR2-fH or mu-fHSCR19–20 2 h prior to a single provocative (secondary) challenge with aerosolized 1% OVA. In both challenge models, 48 h after the last challenge, mice were assessed for airway responsiveness to inhaled methacholine and biomark- ers in bronchoalveolar lavage (BALF). Treatment with mu-CR2-fH significantly reduced AHR, eosinophilic airway inflammation and goblet cell hyperplasia, accompanied by decreased C3a and Th2 cytokine levels in BALF, in both the primary and secondary chal- lenge models. Conversely, mu-fHSCR19-20 greatly increased AHR, C3a generation and eosinophilia. These data demonstrate that fac- tor H normally suppresses allergen-induced airway disease and that supplementing its activities has therapeutic potential. doi:10.1016/j.molimm.2009.05.208 O23 Opposing roles for C5aR and C5l2 in allergic asthma Xun Zhang a,∗ , Jörg Köhl a,b a Division of Molecular Immunology, Cincinnati Children’s Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, OH, USA b Institute for Systemic Inflammation Research, University of Lübeck, Lübeck, Germany Allergic asthma is a chronic inflammatory disease of the upper airways. It is well appreciated that maladaptive Th2-biased immune responses promote the allergic phenotype, however, the mecha- nisms that initiate such responses remain elusive. Many allergens such as house dust mite (HDM)-derived proteins have protease activity which can cleave C3 and C5 into C3a and C5a. In previ- ous studies, we have shown that C5a can mediate both pro- and anti-allergic properties. During allergen sensitization, C5a protects from the development of maladaptive Th2 immunity whereas in an established allergic environment it acts as a strong proinflamma- tory mediator. C5a exerts its effector function mainly through C5aR (CD88) but can also bind to C5L2, a 7TM receptor uncoupled from G-proteins. The role of C5L2 in allergic asthma is unclear. Here, we describe opposing roles for C5aR and C5L2 in the development of airway hyperresponsiveness (AHR), eosinophilic inflammation, Th2 cytokine production (IL-4, IL-5 and IL-13) and IgE production in two models of experimental allergy, i.e. HDM and ovalbumin-induced allergic asthma. C5aR -/- mice suffer from increased eosinophilic inflammation, Th2 cytokine and IgE production as compared with wildtype (WT) controls, whereas AHR is unchanged. In contrast, eosinophil numbers, Th2 cytokine production, IgE serum concen- tration and AHR are substantially lower in C5L2-deficient mice than in WT. In fact, C5L2 -/- mice exhibit a phenotype which is essentially the same as that observed for C3aR -/- mice. These data suggest that C5L2 either suppresses the protective effects of C5aR signal- ing during allergen sensitization and/or acts synergistically with C5aR signaling to promote inflammation during the allergic effec- tor phase. To differentiate between the two possibilities, we are in the process of specifically targeting C5aR signaling in C5L2 -/- mice in the HDM model of pulmonary allergy. doi:10.1016/j.molimm.2009.05.209 O24 Proteases from the fungal allergen Aspergillus regulate airway epithelial expression of complement component C3 and its acti- vation fragment C3A Eva Morschl a,∗ , Anne T. Bell a , Paul Porter b , David B. Corry b , Scott M. Drouin a a Research Center for Immunology and Autoimmune Diseases, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, The University of Texas Health Science Center at Houston, USA b Departments of Medicine and Immunology, Baylor College of Medicine, Houston, TX 77030, USA Our laboratory has established a prominent role for C3a in airway obstructive diseases by demonstrating the regulation of air- way epithelial mucins by C3a and its receptor in rodent models of allergic airway disease. To investigate the mechanisms leading to complement activation, C3a generation, and mucin expression, we examined the activation of complement by proteases from the fungal allergen Aspergillus in cultures of primary mouse airway epithelium.