ORIGINAL PAPER Anti-tumor necrosis factor-a antibody treatment reduces pulmonary inflammation and methacholine hyper-responsiveness in a murine asthma model induced by house dust J. Kim, L. McKinley, S. Natarajan, G.L. Bolgos, J. Siddiqui, S. Copeland and D. G. Remick Department of Pathology, University of Michigan Medical School, Ann Arbor, MI , USA Clinical and Experimental Allergy Correspondence: Jiyoun Kim, Department of Pathology, University of Michigan Medical School, M2210 Med Sci I, 1301 Catherine Road, Ann Arbor, MI 48109-0602, USA. E-mail: jiyoukim@umich.edu Summary Background/Aims Recent studies documented that sensitization and exposure to cockroach allergens significantly increase children’s asthma morbidity as well as severity, especially among inner city children. TNF-a has been postulated to be a critical mediator directly contributing to the bronchopulmonary inflammation and airway hyper-responsiveness in asthma. This study investigated whether an anti-TNF-a antibody would inhibit pulmonary inflammation and methacholine (Mch) hyper-responsiveness in a mouse model of asthma induced by a house dust extract containing both endotoxin and cockroach allergens. Methods A house dust sample was extracted with phosphate-buffered saline and then used for immunization and two additional pulmonary challenges of BALB/c mice. Mice were treated with an intravenous injection of anti-TNF-a antibody or control antibody 1 h before each pulmonary challenge. Results In a kinetic study, TNF-a levels within the bronchoalveolar lavage (BAL) fluid increased quickly peaking at 2 h while BAL levels of IL-4, IL-5, and IL-13 peaked at later time-points. Mch hyper-responsiveness was measured 24 h after the last challenge, and mice were killed 24 h later. TNF inhibition resulted in an augmentation of these Th2 cytokines. However, the allergic pulmonary inflammation was significantly reduced by anti-TNF-a antibody treatment as demonstrated by a substantial reduction in the number of BAL eosinophils, lymphocytes, macrophages, and neutrophils compared with rat IgG-treated mice. Mch hyper-responsiveness was also significantly reduced in anti-TNF-a antibody-treated mice and the pulmonary histology was also significantly improved. Inhibition of TNF significantly reduced eotaxin levels within the lung, suggesting a potential mechanism for the beneficial effects.These data indicate that anti-TNF-a antibody can reduce the inflammation and pathophysiology of asthma in a murine model of asthma induced by a house dust extract. Keywords antibodies, chemokines, cytokines, eosinophils, lipopolysaccharide Submitted 6 January 2005; revised 2 September 2005; accepted 17 October 2005 Introduction Asthma is a complicated chronic inflammatory disease of the airways characterized by reversible airway obstruc- tion, inflammatory mediator production, and airways hyper- responsiveness (AHR) [1]. Following exposure to allergens, numerous inflammatory cells and structural cells are activated such as macrophages, eosinophils, lymphocytes, and epithelial cells [1]. Upon activation, several inflammatory changes in the airways are triggered with the subsequent release of a wide variety of immuno- modulator molecules into the airway [2]. Asthma is known as a T helper type 2 (Th2) disease with a specific cytokine profile including IL-4, IL-5, and IL-13 [3]. How- ever, recent publications suggested that other cytokines categorized as T helper type 1 are also associated with asthmatic pulmonary inflammation in animals as well as in humans [4, 5]. TNF-a, a potent pro-inflammatory mediator, plays various roles in the immunoregulation of asthma such as alteration of bronchial hyper-responsive- ness [6], airway infiltration of neutrophils [7], activation of airway smooth muscle [8], activation of myofibroblasts [9], and changes in vascular permeability [10] including up-regulation of adhesion molecules such as E-selection, vascular cell adhesion molecule-1 and intercellular adhe- sion molecule-1 [11, 12]. In addition, TNF-a plays an Clinical and Experimental Allergy, 36, 122–132 c 2006 Blackwell Publishing Ltd