• Correlation of changes in basophil receptor occupancy with a reduction in maximum symptom days, inhaled corticosteroid dosage, sputum, and peripheral blood eosinophils, and frequency of exacerbations [ Time Frame: 1.5 years ] [ Designated as safety issue: No ]
  

• Effect of omalizumab therapy on basophil activation markers [ Time Frame: 1.5 years ] [ Designated as safety issue: No ]
  
• Effect of omalizumab therapy on the skin test response to allergen and correlation of this change in skin test endpoint titration with maximum symptom days [ Time Frame: 1.5 years ] [ Designated as safety issue: No ]
  
• Effect of omalizumab therapy on the skin test response to allergen and correlation of this change in skin test endpoint titration with inhaled corticosteroid dosage, sputum and peripheral blood eosinophils, and frequency of exacerbations [ Time Frame: 1.5 years ] [ Designated as safety issue: No ]
  

Immunoglobulin E (IgE) is important in the development of allergic responses and may determine asthma severity. Omalizumab is a man-made monoclonal antibody that directly blocks the cause of allergic reactions. There are three main objectives to this study. The first is to gain an understanding of how omalizumab affects cells involved in the immune response. The second objective is to determine whether response to omalizumab is influenced by exposure to environmental factors, including allergens and viral infections. The third objective is to determine what clinical markers can be used to determine which patients would most benefit from omalizumab therapy. This study will evaluate the immune and allergic responses of inner-city children with moderate to severe asthma who are receiving omalizumab or placebo as part of a parallel study (Inner-City Anti-IgE Therapy for Asthma).

Nasal secretions will be collected from all participants at the beginning of this study, toward the middle of the study, and with each asthma exacerbation requiring a clinical visit. Some participants will participate in either the basophil or T-cell studies and associated procedures. These studies require blood collection at five study visits. Sputum collection will occur at four study visits. Those participants involved in the basophil studies will also undergo skin testing at three study visits.