Allergic asthma is caused primarily by an inappropriate CD4+ Th2 response, which results in symptoms mediated by Th2 cytokines, including IL-13 provoking airways hyperresponsiveness and mucus production, IL-4 promoting the production of antigen specific IgE, and IL-5 inducing eosinophilia [2]. The gene discussed is CD4; the disease is allergic asthma.