T helper 2 cells (Th2 cells) and type 2 cytokines (e.g., IL-4, -5 and -13) promote airway eosinophilia, bronchial hyperresponsiveness, mucus overproduction, airway remodeling and immunogloubulin E (IgE) synthesis in asthma [2] (Figure 1). The gene discussed is IL4; the disease is asthma.