The proposed study is a phase II clinical trial of TNFR:Fc therapy in a segmental allergen bronchoprovocation model of atopic asthma. The goal of this study is to assess whether inhibition of tumor necrosis factor (TNF) bioactivity can attenuate airway inflammation in mild-to-moderate allergic asthmatics. This protocol will utilize a randomized, double-blind, placebo-controlled trial design. TNF bioactivity will be inhibited via systemic administration (e.g., subcutaneous injection) of a dimeric fusion protein consisting of the extracellular ligand- binding domain of the 75-kilodalton TNF receptor linked to the Fc portion of human IgG1 (TNFR:Fc, Immunex). The data generated by this study will address the utility of anti-TNF therapy for patients with asthma.